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
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