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
