I have experienced some desense on the past two passes of FO-29, so after this pass, I checked all the connectors in my system.
Turns out one of the elements of my Elk antenna was very slightly loose. Tightened it up and I don't hear any hash at all on my 435 MHz receive. It doesn't take much to throw everything out of whack! 73, Paul, N8HM On Mon, Jan 20, 2014 at 9:02 PM, Greg D <ko6th.g...@gmail.com> wrote: > Hi Art, > > Yep, corrosion is a great source for harmonics. I had a similar problem > with AO-40, only mine turned out to be the relay contacts on the 70cm > antenna's RHCP / LHCP relay. Cycle them a few times and things quieted > down. But I only heard the problem when I was aimed at the big oak tree > behind our house, which was odd because the 70cm transmit antenna was > literally a few inches away from the edge of the 2.4 ghz receive dish. > Never heard of a tree acting as a diode before. Maybe the squirrels were up > to something... > > Greg KO6TH > > > > kc6...@cox.net wrote: >> >> Greg, >> I had a problem with 70cm jamming 2401 down link many years ago. The >> problem >> turned out to be corrosion between the coax connector shell and the >> aluminum >> antenna element. Cleaning up the connection solved the problem. The >> corrosion acts like a diode and will make enough 3 order products to trash >> any receiver. Use liquid electrical tape or non-corrosive (doesn't smell >> like vinegar) silicon seal to keep these connections dry and clean. >> Art, KC6UQH >> >> -----Original Message----- >> From: amsat-bb-boun...@amsat.org [mailto:amsat-bb-boun...@amsat.org] On >> Behalf Of g0...@aol.com >> Sent: Monday, January 20, 2014 1:23 AM >> To: ko6th.g...@gmail.com; kq...@verizon.net; w4...@gte.net; >> amsat-bb@amsat.org >> Subject: [amsat-bb] Re: 145 MHz signal blocking 435 MHz downlink >> >> >> Hi Greg. >> >> Most decent VHF transmitters will already have a pretty good LPF on the >> output to reduce the harmonics. >> However, receivers these days tend to be DC-Daylight, so frequently need >> a >> filter to prevent 'blocking' by unwanted high level signals. In that case >> preventing the VHF coming into the UHF receiver can be important >> >> Thanks >> >> David >> >> >> -----Original Message----- >> From: Greg D <ko6th.g...@gmail.com> >> To: Jim Jerzycke <kq...@verizon.net>; w4tas <w4...@gte.net>; 'AMSAT >> Mailing >> List' <amsat-bb@amsat.org> >> Sent: Mon, 20 Jan 2014 3:47 >> Subject: [amsat-bb] Re: 145 MHz signal blocking 435 MHz downlink >> >> >> I know this has been answered before, but I forget. Given one Diplexer, >> is >> it better to put it on the Tx side to limit the 3rd harmionic going out, >> or >> better on the Rx side to limit the VHF fundamental coming in? >> Tony's diagram shows the later; I would have thought the former would be >> more effective (hitting the problem at its source). >> >> Greg KO6TH >> >> >> Jim Jerzycke wrote: >>> >>> Yep, been using one of those for years! >>> >>> I have a Sinclair Labs unit that provides 100dB rejection outside of >>> the 2 Meter band. >>> >>> Jim KQ6EA >>> >>> >>> On 01/19/2014 07:32 PM, w4tas wrote: >>>> >>>> I would also suggest a low pass filter on the two meter transmitter. >>>> A diplexer will work well for this also. >>>> This will reduce the third harmonic which is causing your problem. >>>> >>>> Good luck, >>>> >>>> >>>> >>>> >>>> -----Original Message----- From: Jim Jerzycke >>>> Sent: Sunday, January 19, 2014 2:09 PM >>>> To: amsat-bb@amsat.org >>>> Subject: [amsat-bb] Re: 145 MHz signal blocking 435 MHz downlink >>>> >>>> Buy a diplexer, and connect it as shown in the linked article: >>>> >>>> >>>> http://www.amsat.org/amsat-new/articles/Mode-J/ >>>> >>>> I also tilt both of my Yagis so they're 45* to the boom, which makes >>>> them 90* to each other. >>>> >>>> Yes, I lose some signal on terrestrial use, but ti helped cut the >>>> coupling, and desense, down quite a bit. >>>> >>>> 73, Jim KQ6EA >>>> >>>> On 01/19/2014 06:56 PM, Gabriel - EA6VQ wrote: >>>>> >>>>> Hi all, >>>>> >>>>> I have a coupling problem in my station when trying to work FO-29. >>>>> My 2m >>>>> signal is completely blocking the 435 MHz downlink, and so I can't >>>>> hear my signal off the satellite. I guess it must be something >>>>> related to the distance between the two yagis. (I use the >>>>> terrestrial horizontal yagis you can see at >>>>> http://www.dxmaps.com/jm19hn.html ). With mode-B satellites there is >>>>> no problem. I have tried it with two different 435 receivers, and >>>>> it's exactly the same. >>>>> >>>>> Anyone has had this problem o have an idea of the possible reason? >>>>> And what >>>>> is more important, of some way to solve it? >>>>> >>>>> Thanks for any possible help. >>>>> >>>>> 73. Gabriel - EA6VQ >>>>> _________________________________________________________ >>>>> Web-Site: HTTP://www.dxmaps.com >>>>> VQLog 3.1 (build 78): HTTP://www.vqlog.com >>>>> _________________________________________________________ >>>>> >>>>> >>>>> _______________________________________________ >>>>> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the >>>>> author. >>>>> Not an AMSAT-NA member? Join now to support the amateur satellite >>>>> program! >>>>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >>>>> >>>> _______________________________________________ >>>> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. >>>> Not an AMSAT-NA member? Join now to support the amateur satellite >>>> program! >>>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >>>> >>> _______________________________________________ >>> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. >>> Not an AMSAT-NA member? Join now to support the amateur satellite >>> program! >>> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >> >> _______________________________________________ >> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. >> Not an AMSAT-NA member? Join now to support the amateur satellite program! >> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >> >> _______________________________________________ >> Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. >> Not an AMSAT-NA member? Join now to support the amateur satellite program! >> Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb >> > > _______________________________________________ > Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. > Not an AMSAT-NA member? Join now to support the amateur satellite program! > Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
