tag:blogger.com,1999:blog-17167812093859285842024-02-19T05:26:14.453-05:00Audio, etc.chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.comBlogger11125tag:blogger.com,1999:blog-1716781209385928584.post-86102286805488759062021-11-11T05:24:00.005-05:002022-12-08T20:53:31.877-05:00Interchannel Subsample Delays in Commodity USB Audio Interfaces<h3 style="text-align: left;">Summary</h3><p style="text-align: left;">Some USB audio interfaces suffer from left/right output channel delays which tend to be at subsample magnitude, manifesting as frequency-dependent phase distortion.</p><h3 style="text-align: left;">Test results</h3><p style="text-align: left;">Some had interchannel delays, some did not: <br /></p><p style="text-align: left;"><span style="color: red;">Subsample Delay:</span> Behringer UCA202 (ID 08bb:2902 Texas Instruments PCM2902 Audio Codec)</p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitlJ3fHdqaJqLOzx97OR1NeOtzNRJ3Bq_q8En_lF45TxNFn16OSpQnfywZjB-g7m-g8yO0pJoUrMYPmDEXwH-7IiuNxLtkgUVcFkyf1_RroPdNb4iNL5RV6oGgVci4IuiURrx7pfKJiDY/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="1536" data-original-width="2048" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEitlJ3fHdqaJqLOzx97OR1NeOtzNRJ3Bq_q8En_lF45TxNFn16OSpQnfywZjB-g7m-g8yO0pJoUrMYPmDEXwH-7IiuNxLtkgUVcFkyf1_RroPdNb4iNL5RV6oGgVci4IuiURrx7pfKJiDY/" width="320" /></a></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj57EWkHVIIqBVQWEGdvk3ruIAPk4ST6FGeF_XyiI2i4KSxAaYV0AC0ek39thc81nDmm-ux95tCL-QYXXZBWfMPjJHfyBFCWWRT9L0cH-uJGa7i7dxCnNKkO4aU4jORqKrZ2a_V1VhKkxk/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="1536" data-original-width="2048" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEj57EWkHVIIqBVQWEGdvk3ruIAPk4ST6FGeF_XyiI2i4KSxAaYV0AC0ek39thc81nDmm-ux95tCL-QYXXZBWfMPjJHfyBFCWWRT9L0cH-uJGa7i7dxCnNKkO4aU4jORqKrZ2a_V1VhKkxk/" width="320" /></a></div><br /></div><p style="text-align: left;"><span style="color: red;">Subsample Delay:</span> Cable Creation (ID 0d8c:0014 C-Media Electronics, Inc. Audio Adapter [Unitek Y-247A])</p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIChtAaVTyriqQUkatwVvOFoKy1foH5f4aQqErbQLZq6ZH6com9FSTrHKy-njzChIGANIG8mtmjoclqxa93G3OeCJ34aaxrhgXJXz_YOqtzNfopCMicmUE7YxHY3KGo-JFjwcTbvp2RFo/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="2048" data-original-width="1536" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIChtAaVTyriqQUkatwVvOFoKy1foH5f4aQqErbQLZq6ZH6com9FSTrHKy-njzChIGANIG8mtmjoclqxa93G3OeCJ34aaxrhgXJXz_YOqtzNfopCMicmUE7YxHY3KGo-JFjwcTbvp2RFo/" width="180" /></a></div><p style="text-align: left;"><br /> ... the back is featureless black.</p><p style="text-align: left;"> </p><p style="text-align: left;"></p><p style="text-align: left;"></p><p style="text-align: left;"><span style="color: #04ff00;">No Delay:</span> Behringer U-Phoria UMC404HD (and 202HD) (ID 1397:0509 BEHRINGER International GmbH): </p><p style="text-align: left;"></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhayaELmsU3khlPR4e_Ffw16QCI76LkRSuETZ9i9nAoxY4CLcafu1LZyeFZCnCNHq0wnMWWcMNQg-ffr5D7j4BvARbE1zGKKIfrf8ksXjhgrNrnkdO6SkioxIzsYn4cDTWpnMcXADb7WwA/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="768" data-original-width="2807" height="88" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhayaELmsU3khlPR4e_Ffw16QCI76LkRSuETZ9i9nAoxY4CLcafu1LZyeFZCnCNHq0wnMWWcMNQg-ffr5D7j4BvARbE1zGKKIfrf8ksXjhgrNrnkdO6SkioxIzsYn4cDTWpnMcXADb7WwA/" width="320" /></a></div><br /> <p style="text-align: left;"><span style="color: #04ff00;">No Delay:</span> Early 2000s unbranded white USB audio dongle, UMD-10 (ID 074d:3556 Micronas GmbH Composite USB-Device):</p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyqz2vASKbSRNstoqSvDffW6V_6LBt4RDW7COWvxl8lV46cVJZkcy-XgtDt7B7nASDBQy-z2i_HlbxqGJWAJTyOKuzyOTpUhtBuveleP9YSeijIL3sfeipNXvfh4HdJS1GsT3aaqfptuE/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="2048" data-original-width="1536" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgyqz2vASKbSRNstoqSvDffW6V_6LBt4RDW7COWvxl8lV46cVJZkcy-XgtDt7B7nASDBQy-z2i_HlbxqGJWAJTyOKuzyOTpUhtBuveleP9YSeijIL3sfeipNXvfh4HdJS1GsT3aaqfptuE/" width="180" /></a></div><br /><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyDDgo9wXfsY06rq3rN4NEOnK-iGW5AdHHeTE9iP-U1WzTtOEv4Knpk6ZFL_0Oi78kmgNAMOxG_d-d4gdCyLBjOL8r43Ss3qZJlG_H6V60eMimXg3oA3APc58mVUSGUIGOqGnWgQX8kPs/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="2048" data-original-width="1536" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhyDDgo9wXfsY06rq3rN4NEOnK-iGW5AdHHeTE9iP-U1WzTtOEv4Knpk6ZFL_0Oi78kmgNAMOxG_d-d4gdCyLBjOL8r43Ss3qZJlG_H6V60eMimXg3oA3APc58mVUSGUIGOqGnWgQX8kPs/" width="180" /></a></div><br /><br /><p style="text-align: left;"><br /></p><h3 style="text-align: left;">Significance Of Delays</h3><p style="text-align: left;">For users who strictly listen casually, these phase issues are negligible and possibly an enhancement. All of these interfaces were enjoyable.<br /></p><p style="text-align: left;">For producing audio content, I don't recommend these devices- even for casual listening- as they can train the listener to prefer this phase distortion and develop a habit of expecting it in the content they produce.</p><p style="text-align: left;">The consequent phase distortion is unacceptable for pro audio for obvious reasons, and ham radio use when encoding I/Q streams, as they will introduce frequency-dependent imaging at baseband.</p><h3 style="text-align: left;">Discovery<br /></h3><p style="text-align: left;">James Ahlstrom's <a href="http://james.ahlstrom.name/phase_corr.html">extensive write-up</a> illustrated the issue of between-channel (left/right) sample delays in some consumer computer audio interfaces introducing phase distortion and imaging on transmission and receive when using in-phase/quadrature (I/Q) intermediate frequency in software-defined transceivers.</p><p style="text-align: left;">Especially of note was the image on the writeup labeled <i>"Phase correction at fixed VFO for the 40 meter band"</i> which showed a ramping of phase adjustment whose deviation increased linearly with frequency away from center (zero Hz).</p><p style="text-align: left;">In practice, compensating for phase was difficult because the offset would change between power-ups of the device. The linear nature of the phase distortion hinted that there may still be between-channel time delay despite optimal sample delay settings, pointing to the possibility that there is a sub-sample delay happening internally with these interfaces. In other words, though these devices generally max out at 48khz sample rates to the user, their internal sampling rate may be much higher, then down-sampled within the chip, possibly to introduce steeper anti-aliasing filters for better frequency response at a reduced price.</p><p style="text-align: left;">A compensatory subsample delay was achieved in GNU Radio Companion by first upsampling the stream by an arbitrarily large number (i.e. 10) with no antialiasing filters, applying the delay to said stream, applying an antialiasing lowpass followed by a decimator. This causes the delay to still manifest as frequency-dependent phase shift.</p><p style="text-align: left;">This addressed the issue very well - at least until a reboot. There was no need to apply additional phase corrections in quisk. Delays tended to be on the order of 0.5-1.5 samples.</p><p style="text-align: left;">Adjustments had to be made with each use and it's far more practical to use a proper audio interface which doesn't have these issues. I had good luck with the Behringer UMC***HD interfaces, pending frequency content is kept below 45khz, above which introduces spurs as found in this <a href="https://gearspace.com/board/so-much-gear-so-little-time/1312956-need-help-getting-frequency-phase-response-behringer-umc404hd.html">forum thread</a>.</p><h3 style="text-align: left;">Test Proofs</h3><p style="text-align: left;">Testing was performed by a Behringer UMC404HD. It was verified by engaging the mono switch, and routing its headphone output to inputs 1/2 and checking the sample alignment with a 20khz sine with 192khz sample rate. This means every sample output from a tested interface at 48khz would have a 4-sample-long sample as seen by the UMC404HD at 129khz:<br /></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhx2XFBGx3DDLWt5jLWcaQroEDcwnwBRy-f0Pc1mqndKvO2S1O_UZmQlpQ7yLT-FVIo9SZTOmfDf_XfcuO7j5QgQRUpx-DU-G-E9HkcUP_D772ru3CbTkRXBpu9VXAoan6pgPd9M-Xdpss/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="447" data-original-width="1392" height="103" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhx2XFBGx3DDLWt5jLWcaQroEDcwnwBRy-f0Pc1mqndKvO2S1O_UZmQlpQ7yLT-FVIo9SZTOmfDf_XfcuO7j5QgQRUpx-DU-G-E9HkcUP_D772ru3CbTkRXBpu9VXAoan6pgPd9M-Xdpss/" width="320" /></a></div><p style="text-align: left;"></p><p style="text-align: left;"></p><p style="text-align: left;"></p><p style="text-align: left;"></p><p style="text-align: left;"><br />Sine generation is with GNU Radio Companion: </p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOE4O1RSaHB7Ep_wqKqebgH5Od4101x-HVH-tvICAsd10qNNfwY5ZqKTHDYp3GLjKwpLMrwbuDAnoOYqkcgkt5iS0FteX9Nzpirg5EbxREe3ibo_7aLrLXqmTlBhQy5ExEbONoOGDP0GQ/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="339" data-original-width="895" height="121" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhOE4O1RSaHB7Ep_wqKqebgH5Od4101x-HVH-tvICAsd10qNNfwY5ZqKTHDYp3GLjKwpLMrwbuDAnoOYqkcgkt5iS0FteX9Nzpirg5EbxREe3ibo_7aLrLXqmTlBhQy5ExEbONoOGDP0GQ/" width="320" /></a></div><br />Sometimes subsample anomalies are hard to see if the offset is close to 1 sample. Then a 1-sample delay is applied:<p style="text-align: left;"></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuNpQw6KrLCh1E_KyCuP1LAM-RX-gE_erzzP25ud5lkHUGG8SNXnSSvduUEhqaqcpoXhadA_VSEqZpjWDPrr-O_4EnNQS1Oli_O5JklOcJqsA1CWDAn3H3C03XTGX7rHPtXo-qb4qhjBQ/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="307" data-original-width="1086" height="90" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiuNpQw6KrLCh1E_KyCuP1LAM-RX-gE_erzzP25ud5lkHUGG8SNXnSSvduUEhqaqcpoXhadA_VSEqZpjWDPrr-O_4EnNQS1Oli_O5JklOcJqsA1CWDAn3H3C03XTGX7rHPtXo-qb4qhjBQ/" width="320" /></a></div><br />... the remainder is then easier to see in the graphs below.<br /><p style="text-align: left;"></p><p style="text-align: left;">Tested items output a stereo 20khz sine (identical per channel) at 48khz sample rate, routed into channels 1/2 of the UMC404HD.<br /></p><h3 style="text-align: left;">Behringer UCA202 (PCM2902 Audio Codec)<br /></h3><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglz3IbFnWtgF40Dp1KdjuiPAdk8J2SWcrFBBFzLjti0z3_btN9EIQwcb5r8x3vIGygUnIOKXhR7iuzwbwBsR1x5QOSFxjX3BTxvUzAcEFhzz8AsqREDyq3hLJrz9xcXEK-YV1IxumZ_to/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="301" data-original-width="1490" height="65" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEglz3IbFnWtgF40Dp1KdjuiPAdk8J2SWcrFBBFzLjti0z3_btN9EIQwcb5r8x3vIGygUnIOKXhR7iuzwbwBsR1x5QOSFxjX3BTxvUzAcEFhzz8AsqREDyq3hLJrz9xcXEK-YV1IxumZ_to/" width="320" /></a></div>At first glance this looks like a 1-sample offset (4 oversamples), but applying the 1-sample (4-oversample) delay and trying again we still see a roughly quarter-sample misalignment (1 oversample).<p style="text-align: left;"></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKZtTYpa_-TEDSIWzacq5Y1k3crYzzlOZgWKc0CAum5gji6VRo5kDI94ZSXpXM2jZOW7VzxOQ0qcRtfM5NtiaN3w62GKNVUiD9nnkY-jHxufgQDy5S5nbjK1ozjCu-m5F9ezXCrI_XJik/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="292" data-original-width="1485" height="63" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjKZtTYpa_-TEDSIWzacq5Y1k3crYzzlOZgWKc0CAum5gji6VRo5kDI94ZSXpXM2jZOW7VzxOQ0qcRtfM5NtiaN3w62GKNVUiD9nnkY-jHxufgQDy5S5nbjK1ozjCu-m5F9ezXCrI_XJik/" width="320" /></a></div><h3 style="text-align: left;">Cable Creation (Unitek Y-247A) from Amazon</h3><p style="text-align: left;"></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhu_zYXcCqciVE3LCQFZF-2czr_PppVFIMNZ_UuUEDXuxmACEZt2GPLNWTA1V98xDG_E9ZoduTg_fIjA8eXESVCpEWQP7o798dHkXcDXjZNaw4wq0tCtvp8XSFQKa2yiOXTzhIeMr8wtL0/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="296" data-original-width="1490" height="64" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhu_zYXcCqciVE3LCQFZF-2czr_PppVFIMNZ_UuUEDXuxmACEZt2GPLNWTA1V98xDG_E9ZoduTg_fIjA8eXESVCpEWQP7o798dHkXcDXjZNaw4wq0tCtvp8XSFQKa2yiOXTzhIeMr8wtL0/" width="320" /></a></div>... 2 oversample delay, probably 0.5 samples.<br /><br /><h3 style="text-align: left;">Unbranded early-2000s white audio dongle "UMD-10"</h3><p style="text-align: left;"></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"></div><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjvpvymW9KUQeCejoWIl2zYrjQ1OBzRZ1sUhM3V0ZwamayRwSbnLzYa-m6V5I-ebF0i7yElFqyzjPXGn5WYJnaZNJw0_43Aij3KrT1rDcNAzDkfUvm_7xucbxWplvSQUbEY4NNymw7cvA/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="307" data-original-width="1487" height="66" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhjvpvymW9KUQeCejoWIl2zYrjQ1OBzRZ1sUhM3V0ZwamayRwSbnLzYa-m6V5I-ebF0i7yElFqyzjPXGn5WYJnaZNJw0_43Aij3KrT1rDcNAzDkfUvm_7xucbxWplvSQUbEY4NNymw7cvA/" width="320" /></a></div><br />... no issues, even after several plug/unplug cycles.<br /><p style="text-align: left;"></p><h3 style="text-align: left;">Compensation/Proof</h3><p style="text-align: left;">A subsample delay as described above was constructed in GNU Radio Companion 3.8.10 and can be downloaded <a href="https://drive.google.com/file/d/1sLJ9vCO7_wu23r96m9j_VXM-1Wea4JvM/view?usp=sharing">here</a>. A pulseaudio dummy and loopback sink had to be employed to splice it into the audio or I/Q stream.<br /></p><p style="text-align: left;"></p><div class="separator" style="clear: both; text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLcTxLPPpxarGPV4qP-dg9lCUoi1e5MXjU-qKnugKACPL2GLPrVr0EzjSHZ5tKljtHGUFP5QzZOK6DBxWjqgTQuTxTILkEtx5o3O9MLMoTOl2BUOECy921f3qPbuNgQRQAidiw9HJB_b8/" style="margin-left: 1em; margin-right: 1em;"><img alt="" data-original-height="612" data-original-width="1367" height="143" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhLcTxLPPpxarGPV4qP-dg9lCUoi1e5MXjU-qKnugKACPL2GLPrVr0EzjSHZ5tKljtHGUFP5QzZOK6DBxWjqgTQuTxTILkEtx5o3O9MLMoTOl2BUOECy921f3qPbuNgQRQAidiw9HJB_b8/" width="320" /></a></div><br />...this temporarily fixed the issues well.<br /><br /><br /><p style="text-align: left;"></p>chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com1tag:blogger.com,1999:blog-1716781209385928584.post-69978223265004836232013-09-04T06:09:00.000-04:002013-09-04T06:26:08.337-04:00Comparing tropo fade rates of closely-clustered Green Bay TV stationsA comparison of Green Bay TV stations over ~180 mi. tropo to explore whether their fades are in sync or if fades are frequency dependent. These stations were chosen because of their similar power levels, heights, and tight grouping which make them within 5 degrees of each other in relation to the antenna beam. Taken between 1am and 2:30am EST.<br />
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Antenna used was UHF Parabolic Antenna w/ 20-22dB reflector.<br />
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<br />chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-31706991545169630782013-09-03T03:49:00.000-04:002013-09-28T05:44:56.116-04:00UHF Parabolic Antenna (assembly)This is part of a larger article, <a href="http://chuckritola.blogspot.com/2013/08/parabolic-uhf-troposcatter-antenna-for.html" target="_blank">Parabolic UHF Troposcatter Antenna for TV and Amateur Radio</a>.
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjWSe2mdrqdE7ThGNxOj-iCgnWZOF-oEqfUvMaSp3dSkav96Jd1p4ll-Bdehn-DWsp7jMITbXMZUrkBOpuqYY3fDz3O9c9PI1TckElr4Vn4mrH8yCTCzpWqL1iiZlnYW7E9c-FdnJz1Jw/s1600/schematic.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgjWSe2mdrqdE7ThGNxOj-iCgnWZOF-oEqfUvMaSp3dSkav96Jd1p4ll-Bdehn-DWsp7jMITbXMZUrkBOpuqYY3fDz3O9c9PI1TckElr4Vn4mrH8yCTCzpWqL1iiZlnYW7E9c-FdnJz1Jw/s1600/schematic.png" width="226" /></a></div>
<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRn2-5MBgkzvDFD4m1P1PGnMTrvnOD89yJjpVye-vuTcDmFGm5cWzW0lMDMc1fjHGJJZEFsB6hOCpmWOJwq8LHqfYiGD8V9Cs2xzqXaOSOVVAl7Ocd4FWfZZNwUq0EUzfoCD0M_a7AobA/s1600/reflector-0003.jpeg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a>Parts List<br />
<table>
<tbody>
<tr><th>Item</th><th>qty</th></tr>
<tr><td>10' ABS 1.5" DWV pipe</td><td>9</td></tr>
<tr><td>ABS Cement</td><td>8oz</td></tr>
<tr><td>5' ABS 2" DWV pipe</td><td>1</td></tr>
<tr><td><a href="http://www.amazon.com/Skywalker-Signature-Series-U-bolt-Assembly/dp/B009P6JM0E/ref=sr_1_5?ie=UTF8&qid=1380361196&sr=8-5&keywords=antenna+u-bolt">U-bolt Nest Assembly</a></td><td>6</td></tr>
<tr><td>wood, 10' 2x2</td><td>2</td></tr>
<tr><td>10'x6" OSB (smaller pieces mended ok)</td><td>1</td></tr>
<tr><td>20' x 5' galv. screen 2" x 4" grid</td><td>1</td></tr>
<tr><td>4-way ABS Tee, all 1.5"</td><td>2</td></tr>
<tr><td>3-way ABS Tee, all 1.5"</td><td>4</td></tr>
<tr><td>45 deg. ABS elbow, 1.5"</td><td>1</td></tr>
<tr><td>Zip ties, >8"</td>20+<td>
<tr><td>Bolt, 1/4"D x 2"L (or similar) w/ nut</td><td>1</td></tr>
<tr><td>Bolt, 1/4"D x 3"L (or similar) w/ nut</td><td>1</td></tr>
<tr><td>Washer, 1/4" Hole Dia, 1" outer Dia (or similar) w/ nut</td><td>15+</td></tr>
<tr><td>2"x1" copper pipe (instead of washers between swivel plates)</td><td>1</td></tr>
<tr><td>Screw Eye 1/2" eye dia, 1/8" screw Dia. (or similar)</td><td>14</td></tr>
<tr><td>1/8" nylon rope</td><td>~40ft</td></tr>
<tr><td>AntennasDirect C1</td><td>1 or 4</td></tr>
<tr><td>Sealable Container</td><td>1</td></tr>
<tr><td>PPC AquaTight RG-6 conn.</td><td>11+</td></tr>
<tr><td>RG6 raw cable</td><td>20ft+</td></tr>
<tr><td>4:1 RG6 combiner</td><td>1</td></tr>
<tr><td>#10 Copper Wire</td><td>20ft+</td></tr>
<tr><td>3/16" Wire Rope Clamp</td><td>15+</td></tr>
<tr><td>Grounding Clamp (if tripod is new install)</td><td>1</td></tr>
<tr><td>Installed Tripod w/ Rotor</td><td>1</td></tr>
<tr><td>Stainless Steel (or painted steel) plate 6" x 6" x 1/4"</td><td>2</td></tr>
</tbody></table>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi15E07llydkO-UEB77zvhB4KD57JhpzzAkZhl5d_t99gLmouj15y4H-zRBHOIb5ivw9RWnUkYDzuHvodrcNA1vlS1xYesIwQTwIhqfzkPqboVljpw1FVLxcxNROoO-SnY2FoOmxk-8P8E/s1600/assembly.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi15E07llydkO-UEB77zvhB4KD57JhpzzAkZhl5d_t99gLmouj15y4H-zRBHOIb5ivw9RWnUkYDzuHvodrcNA1vlS1xYesIwQTwIhqfzkPqboVljpw1FVLxcxNROoO-SnY2FoOmxk-8P8E/s1600/assembly.png" width="226" /></a><br />
Tool List
<br />
<table>
<tbody>
<tr><td>Saw, blade 18 teeth/inch or coarser (for ABS)</td></tr>
<tr><td>Metal-cutting saw (for trimming bolts)</td></tr>
<tr><td>Metal-cutting oil</td></tr>
<tr><td>Metal file (for deburring trimmed bolts)</td></tr>
<tr><td>Drill w/ metal-capable bits 1/8"-1/4"</td></tr>
<tr><td>Socket wrench (extender recommended)</td></tr>
<tr><td></td><td></td><td></td></tr>
<tr></tr>
</tbody></table>
<br />
<br />
<b>CONSTRUCTION</b><br />
All pieces follow same curvature and thus need only one form.<br />
ABS plastic is light and good strength to weight ratio. Must be painted to resist UV. ABS is invisible to UHF.<br />
Spine of form should be at least 2x2 as it must oppose the force of the bent pipe(s) until they soften.<br />
Legs of form were 2x2<br />
curved surface was 1/2" OSB. Overlap not particularly crucial.<br />
Heat gun in 750 degree mode was used, about 20min per end, pipe was covered in fiberglass insulation. If there is a smell then it is too hot. Hair dryer is too weak.<br />
1100 degree mode is too hot; causes burning.<br />
First pipe was overheated and melted on one end, strap was melted. Still usable.<br />
Second and third were doubled into the form. Strap was used mostly near center to minimize melting. Some negligible deformation due to crushing strap force.<br />
Wanted to avoid using sand so that pipe could be heated inside-out without tedious scanning of the pipe with heat gun.<br />
Duct tape was used dead-center as temporary anchor to hold pipes in place while strap was applied.<br />
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: left; margin-right: 1em; text-align: left;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIOwl8UYuN5O8lNf_B5Efmh8Eg1aXLdsPs3vKaNTSao0lC283tMlBIrmwiNbXPge-ZAVdHdNBiPTiCtkSn2JY755OQfdIwlY1YejFoe8RCsqBDbTwU-MazINgHTSS0NOhOlR4P-BDfpAc/s1600/reflector-0001.jpeg" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgIOwl8UYuN5O8lNf_B5Efmh8Eg1aXLdsPs3vKaNTSao0lC283tMlBIrmwiNbXPge-ZAVdHdNBiPTiCtkSn2JY755OQfdIwlY1YejFoe8RCsqBDbTwU-MazINgHTSS0NOhOlR4P-BDfpAc/s1600/reflector-0001.jpeg" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
Duct tape negligibly gunked on the pipe (not surprising as its max temp is close to ABS softening temp). Consider hi-temp tape or remove prior to heat.<br />
Ideas: Use old shirts/rags as straps pending they have high melting point; more surface area, less crush. Or wrap hi-temp insulative quilt.<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRn2-5MBgkzvDFD4m1P1PGnMTrvnOD89yJjpVye-vuTcDmFGm5cWzW0lMDMc1fjHGJJZEFsB6hOCpmWOJwq8LHqfYiGD8V9Cs2xzqXaOSOVVAl7Ocd4FWfZZNwUq0EUzfoCD0M_a7AobA/s1600/reflector-0003.jpeg" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjRn2-5MBgkzvDFD4m1P1PGnMTrvnOD89yJjpVye-vuTcDmFGm5cWzW0lMDMc1fjHGJJZEFsB6hOCpmWOJwq8LHqfYiGD8V9Cs2xzqXaOSOVVAl7Ocd4FWfZZNwUq0EUzfoCD0M_a7AobA/s1600/reflector-0003.jpeg" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Nylon strap has melted due to<br />
overheating. </td></tr>
</tbody></table>
Not flawless but good enough for the antenna,<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZpCYr-exH_EzEh2TzRugM4bxnDJ6to4OIzM4QaShCyc8IR2GisDErQnXxGjo4pD5lbI-DhDq2cHM9db6s_18unKWdk7qUTKV7JVQViMwMfOh3w58LppY64GVHqlavlRDx6HU8IV5z1R0/s1600/reflector-0006.jpeg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiZpCYr-exH_EzEh2TzRugM4bxnDJ6to4OIzM4QaShCyc8IR2GisDErQnXxGjo4pD5lbI-DhDq2cHM9db6s_18unKWdk7qUTKV7JVQViMwMfOh3w58LppY64GVHqlavlRDx6HU8IV5z1R0/s1600/reflector-0006.jpeg" width="200" /></a>4-way 1.5" tee may be difficult to find as they tend to be banned in plumbing codes. Menards sells in batches in 5 if pre-ordered.<br />
Also consider internet for Tee, as phone searching may be more cost in time.<br />
Mesh attached with zip-ties.<br />
Reflector mesh uses widest squares available without leaking too much of upper frequencies. <a href="http://www.menards.com/main/building-materials/fencing/utility/galvanized/60-x-50-welded-utility-fence/p-1356927-c-5769.htm" target="_blank">2x4" menards</a>. <br />
<br />
1.5" high would be ideal however 2" high will be lighter and losses may be negligible.<br />
If using reciprocating saw, use 18 teeth per inch or coarser.<br />
Cut spine into thirds, be sure to label parts and write which way is 'up' and which way is 'forward' such that curve doesn't end up crooked.<br />
Cut arms into halves, label the direction toward the spine so they don't get reversed and 'forward' as with the spine.<br />
<br />
Dry-fit the parts, sand inside edges of tees with Dremel grinder if deformation of pipes made them too tight.<br />
Glue, ensure arms are going to be parallel with ground and not perpendicular to spine's curve.<br />
Sand down surface and paint white. No primer necessary but multiple coats needed.<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMskvv8YwNrBiR438XOD6Sb-h638tpZBUkpJjStaG2RiBGZz8JUBykLZCT_V-UlKipXNa_2JD35O6UZ1h1p2sBOnEeAMbdn3bxb_Lemrf4lAW1EjEr92WFurZsR5cqu5t-F7b9JZ5sKJc/s1600/reflector-0007.jpeg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgMskvv8YwNrBiR438XOD6Sb-h638tpZBUkpJjStaG2RiBGZz8JUBykLZCT_V-UlKipXNa_2JD35O6UZ1h1p2sBOnEeAMbdn3bxb_Lemrf4lAW1EjEr92WFurZsR5cqu5t-F7b9JZ5sKJc/s1600/reflector-0007.jpeg" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Side-arms must be bent half-at-a-time,<br />
flipped around and bent again.</td></tr>
</tbody></table>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifi10pa4fguJBUkHmmN65k3XpHlGHHhJT8ErssBAzq1Hwpkd1ixSibfsZsx_niuwNxCwWkQp-WHPssmPORfeJbMBajiP2hPAMv7yQlJrcd1ntFCgYLKMGWHVoD3DrX976W6-j9HJf_fAA/s1600/reflector-0005.jpeg" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEifi10pa4fguJBUkHmmN65k3XpHlGHHhJT8ErssBAzq1Hwpkd1ixSibfsZsx_niuwNxCwWkQp-WHPssmPORfeJbMBajiP2hPAMv7yQlJrcd1ntFCgYLKMGWHVoD3DrX976W6-j9HJf_fAA/s1600/reflector-0005.jpeg" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Rest heat gun on elevated<br />
platform to avoid blowing directly<br />
on pipe walls</td></tr>
</tbody></table>
The 3/4" PVC vertical curvature supports on either side of the reflector could have been made of 1.5" ABS as it has similar weight but greater strength due to greater diameter. <br />
Testing finds that PVC softens (and burns) far more easily than ABS.<br />
<br />
<b>Swivel</b><br />
for 1+1/4" dia pipe, used 1+3/4 in-dia u-bolt.<br />
for 1+1/2" ABS, used 2" in-dia u-bolt<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNrZwcO2MNCuCeNpfjpChy7xlJssTM0h11-ZZWAFwgXhy2Yy5L8Oy3jC6-60mzn3dkj12vgg1YnOK5gdgYBg6jZSFthzW_-XoFTDYPI-qMue8ohX8XQxkMjQ88006X-BA4YNRGi5JflCs/s1600/reflector-0008.jpeg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjNrZwcO2MNCuCeNpfjpChy7xlJssTM0h11-ZZWAFwgXhy2Yy5L8Oy3jC6-60mzn3dkj12vgg1YnOK5gdgYBg6jZSFthzW_-XoFTDYPI-qMue8ohX8XQxkMjQ88006X-BA4YNRGi5JflCs/s1600/reflector-0008.jpeg" width="200" /></a>Cut off excess bolt thread to make room. File roughness on bolt after cutting to make easier for nut to thread. The area between the two plates can be separated with all washers or a piece of copper pipe between two washers.<br />
<br />
Optionally paint inside of LNA container with conductive paint or foil to reduce static. Drill holes in LNA container for RG6, add LNA, drill a weep hole
on the lowest part of container to drain accumulated water. Seal around
RG6 and container lid with hot glue (or something better if you have
it). Shown in picture is a <a href="http://www.ham-radio.com/k6sti/balun.htm" target="_blank">98.7MHz choke balun</a> to quell outer shield noise spillage into C1s.<br />
<table>
<tbody>
<tr><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2JaIv3W9i4gXH5FEhyYxR86udhLqHVpQTR7Br-oMnMs-_9C_zjuR0YTnRi1Rm8l5775YpGY1gdxPBL8qRYwH8GnFm-YPlA5pR6v6GZfJxaOSHzQa-NZbEbAPfeMjKWh-mcgRNwvxvcnM/s1600/reflector-0021.jpeg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="200" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2JaIv3W9i4gXH5FEhyYxR86udhLqHVpQTR7Br-oMnMs-_9C_zjuR0YTnRi1Rm8l5775YpGY1gdxPBL8qRYwH8GnFm-YPlA5pR6v6GZfJxaOSHzQa-NZbEbAPfeMjKWh-mcgRNwvxvcnM/s1600/reflector-0021.jpeg" width="150" /></a></td><td><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgR-rUXhsq6gRwzbqPOLO3Q9v4UkQ2vU32Xwj5Vp-3KqCNI9Zt-vIn_xX6NI1vwRf-Z8B1UTZ6YTtY-YENlifQXxVzSS1R2n2pz9AWf1I54w-fTEwuHtr3on6OCcp1CZ4L7aGWZHRbRp50/s1600/reflector-0022.jpeg" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgR-rUXhsq6gRwzbqPOLO3Q9v4UkQ2vU32Xwj5Vp-3KqCNI9Zt-vIn_xX6NI1vwRf-Z8B1UTZ6YTtY-YENlifQXxVzSS1R2n2pz9AWf1I54w-fTEwuHtr3on6OCcp1CZ4L7aGWZHRbRp50/s1600/reflector-0022.jpeg" width="200" /></a></td><td><div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiI8_-MyB4DmnrFGp4mevGU6an_vvyLyX1UMAq4JtemFqO0xTB2MdYPJh6Ssi_5kNDDMuEuA0o4q_c40SQ3nXdkTPFc8QSjcmzb5WvmWA7sz6JQCtyuXpGo-aF9Hj3qtrQuqF5Sf2bc984/s1600/reflector-0024.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="150" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiI8_-MyB4DmnrFGp4mevGU6an_vvyLyX1UMAq4JtemFqO0xTB2MdYPJh6Ssi_5kNDDMuEuA0o4q_c40SQ3nXdkTPFc8QSjcmzb5WvmWA7sz6JQCtyuXpGo-aF9Hj3qtrQuqF5Sf2bc984/s1600/reflector-0024.jpeg" width="200" /></a></div>
<br /></td><td><br /></td></tr>
</tbody></table>
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi2JaIv3W9i4gXH5FEhyYxR86udhLqHVpQTR7Br-oMnMs-_9C_zjuR0YTnRi1Rm8l5775YpGY1gdxPBL8qRYwH8GnFm-YPlA5pR6v6GZfJxaOSHzQa-NZbEbAPfeMjKWh-mcgRNwvxvcnM/s1600/reflector-0021.jpeg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><br /></a></div>
Reflector spine plate attaches to spine with one or two U-bolts; mast plate attaches to mast with one toothed U-bolt. Plates connect with bolt/washers through hole on top right of picture. After parts are attached to mast, all ropes are to attached and secured to screw eyes using wire rope clamps so they may be adjusted easier. (no knotting)<br />
<br />
<table cellpadding="0" cellspacing="0" class="tr-caption-container" style="float: right; margin-left: 1em; text-align: right;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWXIIUKo_TeTMtr3Afs8x2s43DzgMoDTnAlhfdNvmnZ4ulqE78Imaq2DCAOM3jny74CejFKZUx5dlwhTMh1K2pyaKIHUZnF_rpoyG6jkYi41538xn54OG3nSueoYyR_q62Tx5vl3Dozz0/s1600/reflector-0014.jpeg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhWXIIUKo_TeTMtr3Afs8x2s43DzgMoDTnAlhfdNvmnZ4ulqE78Imaq2DCAOM3jny74CejFKZUx5dlwhTMh1K2pyaKIHUZnF_rpoyG6jkYi41538xn54OG3nSueoYyR_q62Tx5vl3Dozz0/s1600/reflector-0014.jpeg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Early version set up on the ground <br />
to find best position for the feed.<br />
Note the distortions in the reflector<br />
before the curvature supports were added.</td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
Antenna was built on the ground and modified there before being finalized. This was also important for finding the focal cloud for feed position and making necessary adjustments prior to roof install. <br />
<div class="separator" style="clear: both; text-align: center;">
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<b>Disclaimers</b><br />
The brands and products mentioned in this article are for
reference and example only and do not constitute an endorsement,
recommendation, or affiliation with any mentioned party. Though this
information is intended to be useful and functional, it is offered AS-IS
without warranty even for safety or fitness for any particular purpose. chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-62366397467418961062013-08-27T23:54:00.000-04:002014-04-09T23:45:04.447-04:00Parabolic UHF Troposcatter Antenna for TV and Amateur Radio<div style="text-align: right;">
</div>
A parabolic UHF antenna <br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhII5KrcVSAwC-rameLOQqSiydoKV3GkBs_BuaJvnU0apwZrP3PpzceOb__WXz8vdE6pcJsKcPB1pDol4ot4RsWePj4vMggRDaRPbAEQ_pzqyqBuMWWc2bA6kkjgyxGDaSJxc_hoKjZ7_A/s1600/reflector-0040.jpeg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhII5KrcVSAwC-rameLOQqSiydoKV3GkBs_BuaJvnU0apwZrP3PpzceOb__WXz8vdE6pcJsKcPB1pDol4ot4RsWePj4vMggRDaRPbAEQ_pzqyqBuMWWc2bA6kkjgyxGDaSJxc_hoKjZ7_A/s1600/reflector-0040.jpeg" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">For scale, top of the 4-element feed is chest-height.</td></tr>
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to investigate the feasibility and challanges of TV and amateur radio over <a href="https://en.wikipedia.org/wiki/Tropospheric_propagation" target="_blank">troposcatter</a> using parabolic reflectors was designed and built.<br />
<br />
Troposcatter enables UHF and microwave signals to be received beyond the horizon limit (~70mi), which is traditionally considered the practical limit for these frequencies. The downside of tropo is <a href="https://en.wikipedia.org/wiki/Signal_fade" target="_blank">signal fading</a> with severe degradation in signal quality and strength which require extreme measures to receive.<br />
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Antenna is dismantled because the 1+1/4" galv. steel rotor mast pipe has bent from stress, causing it to increasingly point toward the ground. With the reflector's narrow beamwidth, this factor became non-negligible fairly quickly and it eventually ceased to perform. Because this started happening sleetfall, ice weight is suspected.<br />
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<b>Results</b><br />
An extremely well-performing antenna which shows that parabolic reflectors are still good for very high gains in the UHF range. It is, however, very high-maintenance and a <strike>hazard</strike> challenge to install. Its tropo reception is unreliable and a lot of time has to be put into its assembly and use. Fade behavior is comparable to that of shortwave, but with ranges of hundreds of miles instead of thousands. Tropo performance likely will vary by location; third-party verification or improvements on this design would be interesting. The experience from this project may be used for fine-tuning future projects.<br />
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<tr><th>Callsign</th><th>Channel</th><th>Distance</th><th>Reliability</th><th>Notes</th></tr>
<tr><td>WLUC</td><td>RF35</td><td>64mi</td><td>99%</td><td></td></tr>
<tr><td>WZMQ</td><td>RF19</td><td>62mi</td><td>80% night, 30% day</td><td>Transmitter is beam-steered away from antenna</td></tr>
<tr><td>WJMN</td><td>RF48</td><td>104mi</td><td>60%</td><td>Night Only</td></tr>
<tr><td>WBAY</td><td>RF23</td><td>188mi</td><td>15%</td><td>Choppy day/night</td></tr>
<tr><td>WCWF</td><td>RF21</td><td>~180mi</td><td>15%</td><td>Choppy day/night</td></tr>
<tr><td>WFRV</td><td>RF39</td><td>~180mi</td><td>15%</td><td>Choppy day/night</td></tr>
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<span style="font-size: x-small;">With deep fading of tropo, figures are given in percent reliability (how often a tuner lock can be acquired) instead of signal strength. Antenna stands 25ft AGL on the side of a shallow <50ft hill.</span><br />
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<span style="font-size: x-small;">Images Copyright <span class="st">©</span>2013 tvfool.com</span></div>
<b>Design</b><br />
This is a 10'x10' offset-feed parabolic reflector made of 2"x4"-grid galvanized steel screen supported by a painted, heat-formed 1.5" ABS DWV pipe frame. The feed consists of four AntennasDirect C1s (SWR <1.5, UHF only, ~30dB attenuation in VHF) spaced approximately 1.5 feet apart and held in position by nylon rope. Each C1's output passes through a Laird Technologies 28A0640-0A2 ferrite choke and converges to a 4-way combiner followed by a Research Communications 9261 LNA (0.4dB NF, UHF only, with upper and lower boundary filtering) prior to downlead, connected via Aquatight PPC. Testing tuner is HDHomeRun. Total calculated weight is approx. 37 pounds. Reflector inclination, feed distance and position are adjustable. Including tripod mount, the structure rises approx. 13 feet off the roof.<br />
<br />
<b>Overdrive</b><br />
Overdrive is a serious concern, which is why the feed and LNA are UHF-only and were selected to reject out-of-band signals. Despite this, there was still some overdrive and resulting harmonic LNA overdrive from WGLI (98.7MHz 200kW@4mi.), possibly due to coax shield spillover making it through the choke at the C1s. Another strong emitter were the various cell towers broadcasting in the upper UHF "white space." These bright stations created blind angles which could not be used for reception of tropo.<br />
<br />
<b>Influences</b><br />
This antenna is inspired by the <a href="http://www.rocketroberts.com/cm4251/cm4251.htm" target="_blank">Channel Master 4251</a> and commercial antennas developed by Wade in an attempt to develop a very light-duty antenna of a similar performance caliber.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcUf2Sm6mwNbFfj03XJva2tpIUilDDkS6W9tNyt9hipdN2op75BM0Vukhvw_VZ0TY8yvPMALdT6k7aONFzr8b3mhg1wvFktizy_d4VP6YiR7uolZXntOBCqqC9j3sfahxx11_Oy-aayuw/s1600/reflector-0036.jpeg" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjcUf2Sm6mwNbFfj03XJva2tpIUilDDkS6W9tNyt9hipdN2op75BM0Vukhvw_VZ0TY8yvPMALdT6k7aONFzr8b3mhg1wvFktizy_d4VP6YiR7uolZXntOBCqqC9j3sfahxx11_Oy-aayuw/s1600/reflector-0036.jpeg" width="320" /></a></td></tr>
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<br />
<b>Performance</b><br />
Extremely good performance: Stations too weak to be received by the stack can be received with this reflector. The calculated (before LNA) gain is approximately 20-22dB at 550MHz with a full beamwidth of about 13 degrees at 3dB contour down. Actual performance is roughly within 3 dB of this calculation. In practice it is aggressively directional and exceeds the granularity of the rotor. It also has a 10dB backlobe and two 12dB rear sidelobes from feed spillover at about 40 degrees. There is a signal strength gap between where line-of-sight reception is lost and the maximum strength of typical tropo. This antenna successfully traverses that gap but with issues more complex than signal strength alone.<br />
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<b>Wind Profile</b><br />
Wind profile is surprisingly good for this antenna because of the minimal materials used, but the feed has a more significant wind profile with its broader surfaces and the added torsion of 7 feet which has no counter-torsion behind the reflector. Leverage, spring action of the mast, and elasticity of the nylon ropes also caused the entire feed to bounce (details in next section) but these did not greatly affect reception.<br />
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<b>Structure</b><br />
Bolstering supportive structure increases wind profile and could potentially <i>decrease</i> durability, particularly near the edges where wind torsion potential is greatest. This antenna's lightweight design required very careful balancing of both the quantity and vectors of loads. Most failures involved screw-eyes (fixed with thicker screw eyes) and rope-slip failures. The ABS frame itself has endured up to winds of up to 45 MPH without direct issue. This delicate balancing means that the failure of one part will result in the cascading failure of additional parts as their torsions and loads become unbalanced. Repairs must be done quickly to avoid further damage.<br />
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<b>Limitations</b><br />
There are many channels whose signal strength should be high enough to acquire a lock but lack the S/N ratio to do so, apparently due to severe multipath-of both static and dynamic varieties which leave the signal quality in poor condition: By the time a signal reaches the antenna is may have traveled hundreds of miles among mountains, temperature inversions and buildings. Further increases in signal strength have diminishing returns in the case of multipath as interference scales up alongside desired signal, with a speculative exception of narrowing the beamwidth. There is also the issue that this antenna is....awfully large.<br />
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<b>Improvements</b><br />
Increasing aperture size is unlikely to happen for practical reasons. There is a lot of promise in using or implementing a more advanced tuner, such as a diversity mobile tuner. Solving multipath would sharply improve performance.<br />
<br />
The original plan was to have a single C1 at the end of the feed.
When this was changed to four C1s the feed became heavier making the antenna front-heavy. This, combined with bouncing of the
feed and ice buildup resulted in the steel rotor mast pipe slowly bending from stress.<br />
<br />
In the future this could be addressed by switching back to a single C1, and compensating for the wider feed
pattern by shortening the feed arm, which would reduce front-weight
greatly. In compensation for needing a shorter focal point, the
reflector curvature would have to be sharpened, resulting in a slightly
increased reflector weight relative to aperture size which would be far compensated by the benefits of the redesigned feed.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFbf9voZvl0_3mT6OXxR_nZzE7MWmhSypcEdE1HBkMmhX6CecisGSlGL488tNkyAplAeqmnFjFggWOCo57ugnas10qtGETrNP3GlAOoZQGrakyxeU2mSNS6un2w6RWGFwIP4DI65XBz7w/s1600/mutlipath-gone-awry-19.png" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" height="164" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjFbf9voZvl0_3mT6OXxR_nZzE7MWmhSypcEdE1HBkMmhX6CecisGSlGL488tNkyAplAeqmnFjFggWOCo57ugnas10qtGETrNP3GlAOoZQGrakyxeU2mSNS6un2w6RWGFwIP4DI65XBz7w/s1600/mutlipath-gone-awry-19.png" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">80% strength and no tuner lock. <br />
An extreme example of multipath gone awry from tropo cells. <br />
(LNA distortion, co-channel and jamming ruled out)</td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
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<br />
<b>Durability</b><br />
Reflector shakes in wind but survives storms without breaking. Effective wind profile is relatively small because of the use of screen, rope and cylindrical pipe. <strike>This antenna will be kept over the winter to test its ice/snow handling</strike>. Dismantled due to mast pipe stress following sleet.<br />
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<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiz4RkBDOhu0mREcf4m6ffkK_eE7tCjRGOComI2mmOHm3OaVC8a-hv6po2qE1f0Al8C7Ek92KvQ312wZb9TR4fN5dpHrLIeMew7G5clKZ4R1-l-yfgfiIA6UvsGlS6GdpGiGEvlIYk-PSs/s1600/bent-antenna-mast-pipe-2014.JPG" imageanchor="1" style="clear: right; margin-bottom: 1em; margin-left: auto; margin-right: auto;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEiz4RkBDOhu0mREcf4m6ffkK_eE7tCjRGOComI2mmOHm3OaVC8a-hv6po2qE1f0Al8C7Ek92KvQ312wZb9TR4fN5dpHrLIeMew7G5clKZ4R1-l-yfgfiIA6UvsGlS6GdpGiGEvlIYk-PSs/s1600/bent-antenna-mast-pipe-2014.JPG" height="150" width="200" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Bent mast pipe</td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
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<br />
<b>Weather</b><br />
Reception is affected dramatically by weather: Humid, calm, clear nights are best while nights preceding a storm are also good while dry and/or windy weather are most detrimental. This antenna can detect lightning as raw signal strength will momentarily spike on lower channels with each strike. Jokingly, 'passive weather radar' may be a better application than HDTV.<br />
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<b>Amateur Radio</b><br />
<strike>70cm (420MHz) feasibility is being investigated.</strike> Dismantled before testing could be done.<br />
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<b>Assembly</b><br />
Sub-article is <a href="http://chuckritola.blogspot.com/2013/09/uhf-parabolic-antenna-assembly.html" target="_blank">here</a>.<br />
<br />
<b>Disclaimers</b><br />
The brands and products mentioned in this article are for
reference and example only and do not constitute an endorsement,
recommendation, or affiliation with any mentioned party. Though this
information is intended to be useful and functional, it is offered AS-IS
without warranty even for safety or fitness for any particular purpose. chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-79862641257950620522013-07-17T02:24:00.000-04:002016-07-18T21:25:04.520-04:00Sweeping spectrum analyzer for FunCube Dongle Pro+<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9-IRtiLwhd8NHwtv7t2c57EAvrBimkW6mNIR_d31AOgI0gnLE2-9X6MlNvVG_wPxSD9zh9cNIYuvEnzabOgoKTHnhSbk4blWamg3pIrg6vBxhAbqb9kPlRf__WKVjPKtFXCXho9HL4VM/s1600/sweep-setup-screenshot.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="94" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9-IRtiLwhd8NHwtv7t2c57EAvrBimkW6mNIR_d31AOgI0gnLE2-9X6MlNvVG_wPxSD9zh9cNIYuvEnzabOgoKTHnhSbk4blWamg3pIrg6vBxhAbqb9kPlRf__WKVjPKtFXCXho9HL4VM/s1600/sweep-setup-screenshot.png" width="200" /></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEi9-IRtiLwhd8NHwtv7t2c57EAvrBimkW6mNIR_d31AOgI0gnLE2-9X6MlNvVG_wPxSD9zh9cNIYuvEnzabOgoKTHnhSbk4blWamg3pIrg6vBxhAbqb9kPlRf__WKVjPKtFXCXho9HL4VM/s1600/sweep-setup-screenshot.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"></a><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdXILJUMfOI_ipWMILisT9L9yAWOzzRnvhJrWyQYLY-huRb3CXwOveizw2VaEMiF7uI07f4REYXO2G30YcY5S6vkm6l1q0pIegk9R8lJXEwdXjtB8ApcQhe333LH5m402PcY1Axha7isM/s1600/spectrum-viewer-screenshot.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="138" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgdXILJUMfOI_ipWMILisT9L9yAWOzzRnvhJrWyQYLY-huRb3CXwOveizw2VaEMiF7uI07f4REYXO2G30YcY5S6vkm6l1q0pIegk9R8lJXEwdXjtB8ApcQhe333LH5m402PcY1Axha7isM/s1600/spectrum-viewer-screenshot.png" width="320" /></a> A GUI-based variable-range sweeping (non-realtime) spectrum analyzer program called fcd-spectrum has been implemented in java for use with the FUNCube Dongle Pro+ SDR. It aims to report approximate input power in units of dBm relative to frequency. Automatically adjusting-and compensating for-gain, fcd-spectrum writes to a .CSV file and has a built-in viewer. Example sweep times are about 1 minute for 88-108MHz and about 2 hours for the entire 150k-2G range. CLI-only mode operation is also supported. This application is licensed under GPL3.<br />
<br />
<i>Note: There are issues with running this software in Mac OSX (see Issues tab on project page) </i><br />
<br />
<a href="https://github.com/cjritola/fcd-spectrum">https://github.com/cjritola/fcd-spectrum</a>chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-20503403802291837572013-04-26T11:54:00.003-04:002013-05-19T04:09:32.551-04:00Ubuntu .deb package for Funcube Dongle Pro+ support in GNURadio CompanionThis .DEB package installs a <a href="http://www.funcubedongle.com/" target="_blank">Funcube Dongle Pro+</a> sourceblock for GNU Radio Companion to Ubuntu. It is built from source posted by <a href="http://github.com/dl1ksv/gr-fcdproplus" target="_blank">DL1KSV</a>, implementing the FCDPP as a complex source and provides variable control to LNA On/Off, Center Frequency, Mixer Gain On/Off, Frequency Correction, and IF Gain from within GNU Radio Companion.<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSUdGINem4RGgVZGWGavfP9ps8ot_Znu1MtIWOh5ZLH9eLXW1It9aBu_rU-WW57ezQUoG2KrNBgLoWsVv-q371yRc3tmW8JJH2Ak_mzz-bhxaVs4x-DgL75cutAL8SwVrhIvgJA6QSqug/s1600/fcdpp-gnuradio.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEhSUdGINem4RGgVZGWGavfP9ps8ot_Znu1MtIWOh5ZLH9eLXW1It9aBu_rU-WW57ezQUoG2KrNBgLoWsVv-q371yRc3tmW8JJH2Ak_mzz-bhxaVs4x-DgL75cutAL8SwVrhIvgJA6QSqug/s1600/fcdpp-gnuradio.png" /></a></div>
<br />
The * * Pro sourceblock which comes standard with GNU Radio will not properly control the * * Pro+ and vice versa. Like the source, the package is licensed GPL. The versioning scheme is <i>year.month.day.branch_name</i> representing the date the code was pulled from git and the git branch name.<br />
<br />
<a href="http://www.blogger.com/goog_1795019979"><br /></a>
<a href="https://docs.google.com/file/d/0BxvD4PHJkNOnazd3V1dDbDZqdUU/edit?usp=sharing">libgnuradio-fcdpp_13.05.16.master-2_amd64.deb</a><br />
<span style="font-size: xx-small;">Built and tested against Ubuntu 13.04 and Ubuntu's gnuradio package (3.6.1).</span><br />
<a href="http://www.blogger.com/goog_1223628890"><br /></a>
<a href="https://docs.google.com/file/d/0BxvD4PHJkNOnTHRXMUs4dGNvZlk/edit?usp=sharing">libgnuradio-fcdpp_13.04.26.master-2_amd64.deb</a><br />
<span style="font-size: xx-small;">Built and tested against Ubuntu 12.10 AMD64 and ubuntu's gnuradio package (3.6.1).</span><br />
<br />
<span style="font-size: xx-small;"><span style="font-size: small;">Following installation, <span style="font-size: small;">t</span>he FCDPP may need to be disconnected and reconnected in order to detect properly.</span></span><br />
<br />
<span style="font-size: x-small;"><i>Note: I am fairly inexperienced with generating .deb packages. If there is a problem with the package please let me know.</i></span>chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com6tag:blogger.com,1999:blog-1716781209385928584.post-79350652871200070622012-09-17T08:11:00.003-04:002012-09-17T08:11:34.359-04:00Format Description Toolkit for Java<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTJ7fJUKzkEBeIpieQyiDKNZRH7-RpIM44zTETCz__aS_8u9VXVyp7FLhj9ssfeF7ZcxYDQPKUEnDC-TXmk6CZ5bvUB21QW2IRok0f6eNduPMR9AndIwODyRJsU58mMcHpxxAte06TJwE/s1600/jfdt.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjTJ7fJUKzkEBeIpieQyiDKNZRH7-RpIM44zTETCz__aS_8u9VXVyp7FLhj9ssfeF7ZcxYDQPKUEnDC-TXmk6CZ5bvUB21QW2IRok0f6eNduPMR9AndIwODyRJsU58mMcHpxxAte06TJwE/s320/jfdt.png" width="226" /></a>A small library to ease parsing and encoding of non-bean files and streams has been implemented,
mapping them to/from Java Beans. This allows the developer to write a
single format description, mapping parsed data to Bean properties
without writing separate code between reading and writing.<br />
<br />
jFDT has the potential to improve development time of larger file and stream parsing projects by minimizing boilerplate code.<br />
<br />
<a href="http://code.google.com/p/jfdt/" target="_blank"> Link To Google Code Project</a>chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-48752598342104872072012-07-15T06:02:00.001-04:002013-03-02T11:04:28.134-05:00Fireworks Display Used As Convolution Reverb IR Source On Music<h3>
Summary </h3>
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggqz2NTA6FgODPoybsdq5MnJU3-qPqRqyYKqjVA4dbC2yhgHVwHOvJ8D7EB5RGQS9_Hj9G4PbYAc8B_-ChDY-dR9J4wKPg3MoVXNCUZ7KI7rKgPYfYmhki-KtzEjcZJnK6TowedPRWkrU/s1600/fireworks-0005.jpeg" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEggqz2NTA6FgODPoybsdq5MnJU3-qPqRqyYKqjVA4dbC2yhgHVwHOvJ8D7EB5RGQS9_Hj9G4PbYAc8B_-ChDY-dR9J4wKPg3MoVXNCUZ7KI7rKgPYfYmhki-KtzEjcZJnK6TowedPRWkrU/s320/fireworks-0005.jpeg" width="320" /></a></div>
A South Range, MI July 4th fireworks display is demonstrated for use as a convolution reverb impulse-response (IR) source applied to music. A Canon Powershot S3IS was used to capture the IR events on-site.<br />
<br />
<span style="font-size: large;">Environment</span><br />
The recording environment was an out door hilly, mildly-mountainous
forested area with partial urbanization, approximately twenty feet from a
highway. Impulse events were approximately 500 feet above ground. Wind and spectator noise were present in the environment and were also recorded. Recorded material was edited in Audacity to mix multiple IR events, ultimately removing the noise by attrition. The resulting impulse was then tapered with the "fade out" function.<br />
<br />
Convolution processed by ConvolveJ<br />
http://code.google.com/p/convolve-j/<br />
<br />
All material including music (c) 2006,2012 Chuck Ritola.<br />
<br />
<a href="http://www.youtube.com/watch?v=nFhFhnjJrl0" target="_blank"><span style="font-size: x-large;">Click Here For Demonstration Video</span></a>chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-37555078496762467082012-07-15T04:48:00.000-04:002012-07-15T04:52:56.997-04:00Java-Based Audio Convolution Utility<h2>
<span style="font-size: small;">Google Code project for straightforward java-based audio convolution utility with PCM-based WAV/RIFF media.</span></h2>
<br />
<i>A simple CLI audio convolution utility was implemented in java as a standalone JAR</i><i> which accepts 44khz signed
WAV files as input and impulse and outputs a 16-bit signed 44khz PCM WAV file.
The utility automatically normalizes the output to prevent clipping
while maximizing volume. </i><br />
<br />
Google Code home page, with download for executable .JAR can be found <a href="http://code.google.com/p/convolve-j/" target="_blank">here</a>.<i> </i>chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-1522661245926795832012-07-15T02:26:00.002-04:002012-07-15T02:46:06.912-04:00<span style="font-size: x-large;">SimpleWAVIO </span><br />
A simple WAV/RIFF I/O library and extensible RIFF parser were developed as a Google Code project licensed under the GPL v.3. Its project page is <a href="https://code.google.com/p/j-simple-wav-io/" target="_blank">here</a>.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<div class="separator" style="clear: both; text-align: center;">
</div>
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjah7q6uBpfc6SLk8hMH_qd5LYg1CT2p9B7jAZI-rg5bah7FU_evz8dJeS5LCOAGcUtw2SNeUYtf8pLtDaccmOEJQxX80l7f0m0-Bn8TbBf1iqhF6nzKayb0lJwQI9sAN-1oKOpnce9roo/s1600/RiffChunkParsing.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="400" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEjah7q6uBpfc6SLk8hMH_qd5LYg1CT2p9B7jAZI-rg5bah7FU_evz8dJeS5LCOAGcUtw2SNeUYtf8pLtDaccmOEJQxX80l7f0m0-Bn8TbBf1iqhF6nzKayb0lJwQI9sAN-1oKOpnce9roo/s400/RiffChunkParsing.png" width="277" /></a><i>This library was made to bridge the abstraction gap in Java's audio API between raw bytes and abstract <tt>DataLine</tt>s, <tt>Mixer</tt>s, <tt>Source</tt>s and <tt>Sink</tt>s.
The pragmatic purpose is to obtain mathematically-usable numerical
representations of PCM WAV/RIFF files in the [-1,1] range which is
customary in digital signal processing.</i><br />
<br />
<i>SimpleWAVIO utilizes a small extensible RIFF parsing/writing library in the package<tt> </tt></i><span style="font-size: x-small;"><tt>com.ritolaaudio.simplewavio.files.*</tt></span><i>. </i><br />
<i>RIFF chunks are identified by their position in the package hierarchy. </i><br />
<br />chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0tag:blogger.com,1999:blog-1716781209385928584.post-87397995586141625962012-07-10T02:14:00.000-04:002016-05-31T08:56:30.757-04:00Double-stack antenna for Over-The-Air TV<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgB4GpcEtVHMlVuLOzd1mfieSpIkeS0LYgWqogXmi8teL0R4GXRoQFYgOMATkiZmdJB3qG_fmHlQ3h8b2wk01689t26wUE7ABPmZfQPgiF_r9Gi32TwK6qyduTNgn8-QgNquuvvonRboDE/s1600/antenna2012-ritolaStack0001.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgB4GpcEtVHMlVuLOzd1mfieSpIkeS0LYgWqogXmi8teL0R4GXRoQFYgOMATkiZmdJB3qG_fmHlQ3h8b2wk01689t26wUE7ABPmZfQPgiF_r9Gi32TwK6qyduTNgn8-QgNquuvvonRboDE/s320/antenna2012-ritolaStack0001.jpeg" width="320" /></a></div>
<br />
A successful attempt was made at gathering over-the-air (OTA) digital television signals in the Houghton/Atlantic Mine/South Range area of the Keweenaw Peninsula. Those stations which were practically watchable are listed below. Actual channels are denoted by the prefix "RF" while contained virtual/subchannels are listed below them, noting their respective network and resolution. (480 is analog NTSC equivalent). These channels were also watchable without the amplifier, however tropo scatter required the amplifier.<br />
<br />
WBKP(RF5) 4.5mi<br />
5.1 - ABC 720<br />
5.2 - CW 480<br />
<br />
WNMU(RF13) 64mi<br />
13.1 - PBS 720<br />
13.2 - PBS 480<br />
13.3 PBS "Plus" 480<br />
<br />
WLUC(RF35) 64mi <br />
6.1 - NBC 1080<br />
6.2 - FOX 480<br />
<br />
<br />
<b>Scenario</b><br />
<br />
The antenna site is in an area known for direct lightning strikes, on a shallow south side of a copper-rich hill, approximately 1/4 mile from the hill's peak. To the north is a larger hill which mostly obfuscates LOS to Houghton/Hancock. The property is less than 3 miles from a major power junction, with 3 high-voltage lines within this radius. The site is also subject to blizzard and snow during winters. Temperature is slightly milder than typical midwest.<br />
<br />
<div class="separator" style="clear: both; text-align: center;">
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6abiw-F9nJpMQVOvqjYXAeklff-ETRjARNyIwNPV7YRwjdBAFDE8jX7aR_vFcMXMx1REQR7fl8N0Vk3YYQRSt4DR90YlE1Y2tayM8udUxPeSX3zJcvQeXt1Kj2jfxMwIfHzgFcNVTgQk/s1600/antenna2012-ritolaStack0002.jpeg" imageanchor="1" style="margin-left: 1em; margin-right: 1em;"><img border="0" height="240" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEh6abiw-F9nJpMQVOvqjYXAeklff-ETRjARNyIwNPV7YRwjdBAFDE8jX7aR_vFcMXMx1REQR7fl8N0Vk3YYQRSt4DR90YlE1Y2tayM8udUxPeSX3zJcvQeXt1Kj2jfxMwIfHzgFcNVTgQk/s320/antenna2012-ritolaStack0002.jpeg" width="320" /></a></div>
<br />
The area has several powerful FM stations within a 10 mile radius, two of which are 100kW and the rest in the 6-30kW range. This becomes relevant later on. Most equipment is either passed down or was readily at hand except for the ULNA, ground wire, tuner, and wifi bridge.<br />
<br />
<b>Design and Configuration</b><br />
<div class="separator" style="clear: both; text-align: center;">
</div>
<table align="center" cellpadding="0" cellspacing="0" class="tr-caption-container" style="margin-left: auto; margin-right: auto; text-align: center;"><tbody>
<tr><td style="text-align: center;"><a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEir8pUHCvcxmIumtMPK_JDR0z4xZhxFAhGKDBkW_DL0BvJkuhyphenhyphenoxSiyH6EbIFdK7qYYZRBbNj9G1jga16g03lMShj-a8HJ6VFZkVeykfJgL1EMx-RrLfcpFvG99DM_KR_9VjAUF_qr32Nw/s1600/DoubleStackLayout.png" imageanchor="1" style="margin-left: auto; margin-right: auto;"><img border="0" height="225" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEir8pUHCvcxmIumtMPK_JDR0z4xZhxFAhGKDBkW_DL0BvJkuhyphenhyphenoxSiyH6EbIFdK7qYYZRBbNj9G1jga16g03lMShj-a8HJ6VFZkVeykfJgL1EMx-RrLfcpFvG99DM_KR_9VjAUF_qr32Nw/s320/DoubleStackLayout.png" width="320" /></a></td></tr>
<tr><td class="tr-caption" style="text-align: center;">Addendum: The RadioShack FM trap has been moved to between the combiner/splitter and the ULNA</td><td class="tr-caption" style="text-align: center;"><br /></td></tr>
</tbody></table>
<br />
The antenna is a dual vertically-stacked RCA ANT3038XR broadband UHF/VHF attached to a 7 foot mast, fed via RG-6 coaxial to a Lafayette 2-way combiner/splitter which then feeds through a Radio Shack FM trap and eventually to an AbilityHDTV AbilityAmp ULNA/EXT. (20dB NF .7-.9)<br />
<br />
The mast is pointed by an Allied U-100 rotor with a refurbished roof tripod installed atop the southmost end of a 2-storey separated garage, approximately 25 feet above ground level. This location was chosen because it is the farthest elevated area from the dwelling, minimizing personal lightning danger, as well as because it has access to the clearing to the southeast. Gain and impedance charts were not currently available for the RCA antennas.<br />
<br />
A grounding system was added to the tripod using a clamp attached to a #6 copper ground lead which leads downward along the wall, separated and anchored using porcelain high-voltage insulators. The RG-6 downlead runs parallel to the ground wire, spaced at approx. 6 inches. spaced from the wall using screw-in wall anchors.<br />
<br />
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<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj9iR7lgpi2QpNnatxCjND5wIb_V5YP5A2f7bk6gSo1lQCRkge7zPu6Qat9S6ceVR33liunSyXenHqLnLNwuvKYIJ6184KD3eS5sy6GOYWktYqhjHdVfLf0G4lVsK7WkOe3-LqmEhc3_I/s1600/wiring.JPG" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEgj9iR7lgpi2QpNnatxCjND5wIb_V5YP5A2f7bk6gSo1lQCRkge7zPu6Qat9S6ceVR33liunSyXenHqLnLNwuvKYIJ6184KD3eS5sy6GOYWktYqhjHdVfLf0G4lVsK7WkOe3-LqmEhc3_I/s320/wiring.JPG" width="240" /></a></div>
RG-6 downlead passes a drip-loop and a grounding block, electrically tied to the true-ground wire which continues downward to a driven stake and a tie-in with AC ground. Following the grounding block the RG-6 downlead passes through a small caulked hole in the wall into the 2nd storey of the garage.<br />
<br />
To eliminate the need to bury cable, to maximize lightning isolation from the garage, and to ensure best signal quality, a remote-controlled HDHomeRun tuner was used, which can tune to two separate channels simultaneously and send them as a digital stream over ethernet, which could then be bridged to a carefully-configured WiFi network between buildings wirelessly.<br />
<br />
Against the wall, slacked RG-6 is coiled to a 1ft. wide loop then fed through an AbilityAmp DC injector, then to an HDHomeRun LAN-based tuner, whose Ethernet output (100-200MHz) was sent straight down through the floor to the ceiling of the first storey to minimize interference with the antenna array. All of these devices were wall-mounted for neatness. DC power feeds to the wall-mounted devices were strung through a choke magnet as a precaution.<br />
<br />
Ethernet from the HDHomeRun leads northward approx 30 feet and then up through the ceiling/floor back to the north wall, second-storey of the garage to a Netgear WNCE2001, serving as a WiFi bridge into the house LAN. <u>It is crucial to accommodate a LOS, strong and stable connection to the WiFi router of the main dwelling such that the sustained throughput meets or exceeds 42Mbps on both RX and TX</u>; any drops below this threshold would result in video breaks from the HDHomeRun. WPA encryption did not appear to cause problems with this link.<br />
<br />
<b>Overdrive Problems</b><br />
<br />
The proximity to FM became a serious problem: With no amplification, the stack still overdrove the tuner, with 98.7MHz WGLI-FM (100kW@6mi) creating an even harmonic which saturated RF10(~98.7MHz x 2 = ~196MHz) with some bleed into RF9 and RF11 and even interfering with RF13. When power was applied to the ampifier, most of the low-VHF and high-VHF was overdriven, apparently also overdriving the ULNA, with zero signal quality and no receivable stations other than RF5. Pointing the stack toward any of these FM towers worsened the situation.<br />
<br />
A Radio Shack FM trap was installed between the splitter/combiner and the ULNA. This dramatically improved reception and removed the harmonic distortion. The FM trap was moved between the DC injector and HDHomeRun (tuner) with lessened improvement. Consequently the FM trap was returned to in-between the combiner and the ULNA.<br />
<br />
Experimenting with a 54MHz hi-pass filter and clamp-on choke was also performed with inconclusive results.<br />
<br />
<b>Rotor Control</b><br />
<br />
<a href="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih9cC6PriHtnRz1yjA_hG18Qt2vZFREHpYawbsQ5c2JTMPU_ivAoZOcpN__24ioKg_i1P9SOtT6_9EkhplMcmN2aOuUyB3awJ6vbBdCgfqgShOFup-5bWUz5m6oQ5z5GD8jR7lgHX_GVA/s1600/RotorCableLayout.png" imageanchor="1" style="clear: right; float: right; margin-bottom: 1em; margin-left: 1em;"><img border="0" height="320" src="https://blogger.googleusercontent.com/img/b/R29vZ2xl/AVvXsEih9cC6PriHtnRz1yjA_hG18Qt2vZFREHpYawbsQ5c2JTMPU_ivAoZOcpN__24ioKg_i1P9SOtT6_9EkhplMcmN2aOuUyB3awJ6vbBdCgfqgShOFup-5bWUz5m6oQ5z5GD8jR7lgHX_GVA/s320/RotorCableLayout.png" width="226" /></a>The U-100A rotor's control wire was old and cracked and replaced with modified CAT5e cable such that the four twisted pairs were tied together to make the four conductors needed to control the U-100A. All junctions of these wires were done using screw-terminal electrical blocks which were then coated with SPI conductive silver-impregnated paint. At the entry point into the wall, a lightning drain was installed between the rotor-control line's "common" and the antenna's downward ground lead. The possibility of controlling the rotor by ethernet is being considered.<br />
<br />
<b>Disclaimers</b><br />
<br />
The brands and products mentioned in this article are for reference and example only and do not constitute an endorsement, recommendation, or affiliation with any related party. Though this information is intended to be useful and functional, it is offered AS-IS without warranty even for safety or fitness for any particular purpose.<br />
<br />
<br />
<b>Helpful Documentation</b><br />
<br />
<a href="http://www.csgnetwork.com/tvfreqtable.html" target="_blank">TV Frequency Table</a><br />
<br />
<a href="http://www.kyes.com/antenna/antennadex.html" target="_blank">Kyes Antenna Guide</a><br />
<br />
<a href="http://manuals.solidsignal.com/AntInstallGuide.pdf" target="_blank">Channel Master Off-Air Installation Guide (for professional installers)</a><br />
<br />
<a href="http://abilityhdtv.com/info/79/" target="_blank">Tropo Scatter In Da UP</a>chuckritolahttp://www.blogger.com/profile/04879924953220783267noreply@blogger.com0