The more I read about it, the more I expect that the right answer
depends on one's particular receive-side hardware. If it's already got
good out of band filtering, then the hi-pass filter offered by the
posted diagram won't help, since it's aimed at reducing the 2m
fundamental overload. For that, you need to use the 2m port on the Tx
side (Tx to Common, 2m port to antenna, leaving the 70cm port unconnected).
On the other hand, if the receiver pretty wide open, then the 2m
fundamental is the main problem, and the posted receive-side design will
eliminate it before it hits the receive chain.
Yes?
Greg KO6TH
Jim Jerzycke wrote:
Since I use a very good 2 Meter bandpass filter on my 2 Meter output,
I use the diplexer AT the antenna, ahead of the preamp.
Jim KQ6EA
On 01/20/2014 03:41 AM, Greg D wrote:
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
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