To All, The Diplexer also acts as a filter. All solid state transmitters have "White Noise" contributions. If you receive while transmitting the White Noise from the 2M side will desense the 70 cm receiver. The amount of noise typically 60 dB down from the carrier varies with the type of output filter used in the transmitter. Of course this does not apply when working the satellite simplex. A bad diplexer can also be the problem. Soldering is poor in some of these overseas units, also excessive power in a former life will cook the parts inside. A good test with 50 loads and a power meter will tell the condition of the diplexer.
Art, KC6UQH
-----Original Message----- From: amsat-bb-bounces@amsat.org [mailto:amsat-bb-bounces@amsat.org] On Behalf Of Joe Sent: Friday, September 25, 2009 6:43 PM To: Gary "Joe" Mayfield Cc: 'AMSAT-BB' Subject: [amsat-bb] Re: Arrow antenna reconfiguration results - UPDATE
as in the texts below, there is something else going on here.
That Diplexor can not be all that bad. two reasons.
How many db down is the front to side of that antenna?
and I can not imaging someone would sell a diplexor that has greater than 20 db of losses.
because of the statement that how criticalpolarity was with the original, and now the antenna has to be nearly 90 degrees cross polarized to make it drop out uhh
that close to 30 db,
at least 20,,
something else is going on here
Gary "Joe" Mayfield wrote:
Another issue I came across was how wide the beamwidth is of the Arrow Antenna between the Arrow diplexer and the new diplexer. I was wondering
if
this was going to happen and it did. The reason that this happened was
with
the old diplexer, the signal attenuated so much that you had to be pointed right smack dab on the bird, a few degrees off and you lost the signal. Now, with the new diplexer, you can point the beam in the general
direction
and still copy the bird. In most cases I had to turn the beam 90 degrees before I completely lost the downlink! Twisting the antenna to make polarization changes makes absolutely no difference now. This also attributes to the fact that now I'm copying the entire pass without
dropouts
or fades. Makes sense. What I've regained over the lossy diplexer makes
up
for any polarization differences, etc. for a better copiable signal.
Next weekend I will have to try more passes and get a feel of how much
this
system has changed.
73,
Jeff WB3JFS Las Vegas, NV DM26
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