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</o:shapelayout></xml><![endif]--></head><body lang=EN-US link=blue vlink=purple><div class=WordSection1><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>Take a look at this one.<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'>http://www.minicircuits.com/pdfs/LFCG-42+.pdf<o:p></o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><p class=MsoNormal><span style='font-size:11.0pt;font-family:"Calibri","sans-serif";color:#1F497D'><o:p> </o:p></span></p><div><div style='border:none;border-top:solid #B5C4DF 1.0pt;padding:3.0pt 0in 0in 0in'><p class=MsoNormal><b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'>From:</span></b><span style='font-size:10.0pt;font-family:"Tahoma","sans-serif"'> arm-allstar-bounces@hamvoip.org [mailto:arm-allstar-bounces@hamvoip.org] <b>On Behalf Of </b>Doug Crompton<br><b>Sent:</b> Saturday, November 29, 2014 7:50 PM<br><b>To:</b> BeagleBone Black ARM Allstar<br><b>Subject:</b> Re: [arm-allstar] DRA818V VHF and DRA818U UHF Transceiver Modules -- Low Pass filter required!<o:p></o:p></span></p></div></div><p class=MsoNormal><o:p> </o:p></p><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Tahoma","sans-serif";color:black'>It looks like the minicircuits 440mhz filters are pretty effective at the 2nd harmonic but the 2 meter ones not so good. These would be good filters for 440 low power but they still cost over twice as much as the module so unless you have one laying around that kind of defeats the low price point. <br><br><a href="http://www.minicircuits.com/pdfs/VLF-530.pdf" target="_blank">http://www.minicircuits.com/pdfs/VLF-530.pdf</a><br><br><a href="http://www.minicircuits.com/pdfs/VLF-490.pdf/" target="_blank">http://www.minicircuits.com/pdfs/VLF-490.pdf\</a><br><br><a href="http://www.minicircuits.com/pdfs/VLF-180.pdf" target="_blank">http://www.minicircuits.com/pdfs/VLF-180.pdf</a><br><br id=FontBreak></span><b><span style='font-size:16.0pt;font-family:"Calibri","sans-serif"'>73 Doug<br>WA3DSP<br><a href="http://www.crompton.com/hamradio">http://www.crompton.com/hamradio</a></span></b><span style='font-size:16.0pt;font-family:"Calibri","sans-serif"'><br><br></span><span style='font-family:"Calibri","sans-serif"'><o:p></o:p></span></p><div><div class=MsoNormal align=center style='text-align:center'><span style='font-family:"Calibri","sans-serif"'><hr size=2 width="100%" align=center id=stopSpelling></span></div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Calibri","sans-serif"'>Date: Sat, 29 Nov 2014 18:09:32 -0600<br>From: <a href="mailto:w0anm73@gmail.com">w0anm73@gmail.com</a><br>To: <a href="mailto:arm-allstar@hamvoip.org">arm-allstar@hamvoip.org</a><br>Subject: Re: [arm-allstar] DRA818V VHF and DRA818U UHF Transceiver Modules -- Low Pass filter required!<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>I use a lowpass filter on my dra818u module. However, I don't have the test equipment to check the harmonics. I use this filter my rc gear.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>It's a Mini-circuits 15542 low pass filter.<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>73,<o:p></o:p></span></p><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>Chris, w0anm<o:p></o:p></span></p><div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'>On Nov 29, 2014 12:12 PM, "Doug Crompton" <<a href="mailto:doug@crompton.com">doug@crompton.com</a>> wrote:<o:p></o:p></span></p><div><div><p class=MsoNormal style='margin-bottom:12.0pt'><span style='font-family:"Tahoma","sans-serif";color:black'>I only ordered UHF but I suspect they might have the same problem. I will definitely check on a spectrum analyzer when I get them. I think these modules are designed as part of an overall transceiver and the microprocessor, display, output amplifier and filtering are missing. For most people it would not be hard to add the proper filtering but few have the RF tools to measure the results. So we would have to come up with a foolproof filter design that can be easily duplicated. At the same time you don't want it to be physically large as that would defeat at least one of the advantages of theses modules to begin with. I have a large amount of double sided copper PC board and I would probably build a little box out of that and put the filter inside along with the module. It would be a matter of winding a couple of coils on some common small diameter material like a pencil and a couple of chip capacitors. Here are some links I found with a quick search on 2 meter filter design.<br><br><a href="http://ve2zaz.net/LowPass_Notch_Filter/144LowPass432Notch.htm" target="_blank">http://ve2zaz.net/LowPass_Notch_Filter/144LowPass432Notch.htm</a><br><br><a href="http://www.radiomods.co.nz/lowpassfilterpage2m.html" target="_blank">http://www.radiomods.co.nz/lowpassfilterpage2m.html</a><br><br><a href="http://www.g4ztr.co.uk/amateur-radio/construction/2m-low-pass-filter/" target="_blank">http://www.g4ztr.co.uk/amateur-radio/construction/2m-low-pass-filter/</a><br><br><a href="http://dutchrfshop.nl/ham-radio/2-meter-band/print-lowpass-filter.html?___store=en&___from_store=nl" target="_blank">http://dutchrfshop.nl/ham-radio/2-meter-band/print-lowpass-filter.html?___store=en&___from_store=nl</a><br><br>So as Dave pointed out until we come up with some real measurements on these, and possible ways to fix the problem, I would be careful about putting them on anything but a dummy load. If the 2nd harmonic was 6db down running them at the 1/2 watt output level they would be putting out 125mw at twice the frequency. Enough to cause interference out to several thousand feet at least.<br></span><span style='font-family:"Calibri","sans-serif"'><br></span><span style='font-family:"Tahoma","sans-serif"'>I wonder if anyone has looked at some of the cheap handhelds that come in from China on a spectrum analyzer? I guess they are type accepted though so they should be OK.</span><span style='font-family:"Calibri","sans-serif"'><br><br></span><b><span style='font-size:16.0pt;font-family:"Calibri","sans-serif"'>73 Doug<br>WA3DSP<br><a href="http://www.crompton.com/hamradio" target="_blank">http://www.crompton.com/hamradio</a></span></b><span style='font-family:"Calibri","sans-serif"'><o:p></o:p></span></p></div></div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'><br>_______________________________________________<br><br>arm-allstar mailing list<br><a href="mailto:arm-allstar@hamvoip.org">arm-allstar@hamvoip.org</a><br><a href="http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar" target="_blank">http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar</a><br><br>Visit the BBB web page - <a href="http://www.crompton.com/hamradio/BeagleBoneBlackAllstar/" target="_blank">http://www.crompton.com/hamradio/BeagleBoneBlackAllstar/</a><o:p></o:p></span></p></div><p class=MsoNormal><span style='font-family:"Calibri","sans-serif"'><br>_______________________________________________ arm-allstar mailing list <a href="mailto:arm-allstar@hamvoip.org">arm-allstar@hamvoip.org</a> <a href="http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar">http://lists.hamvoip.org/cgi-bin/mailman/listinfo/arm-allstar</a> Visit the BBB web page - <a href="http://www.crompton.com/hamradio/BeagleBoneBlackAllstar/">http://www.crompton.com/hamradio/BeagleBoneBlackAllstar/</a><o:p></o:p></span></p></div></div></div></body></html>