[NLRS] Downconverters

Wed, 11 Dec 2002 08:57:58 -0600

'Morning John.

This is opinion, realize, as I'm not active on satellites.

In any weak-signal situation (and really, satellites are "weak-signal,"
although I'll get an argument there from some people), the closer to the
antenna you can get your receiver and tranmitter, the better off you are !

For the down-link (13cm, not 23cm), cable lengths of a few feet OR LESS are
desirable.  That means the receive pre-amp or the downcoverter is mounted as
close to the antenna feed point as possible.  A downconverter will have a
net GAIN, not loss.  Same with a simple pre-amplifer, although there won't
be as much.  Also, the cable losses will be higher sending 13cm down the
line vs., say, 144MHz.

Up-links are usually not as sensitive, as its easy to generate power, and
let it "heat up the cable."  Depending on how you generate power at 23cm
(tubes, or solid-state) it may be impossible to put the final amp near the
antenna.

Does this help any ?

73 Donn
WA2VOI/0

-----Original Message-----
From: john scherer [mailto:[email protected]]
Sent: Wednesday, December 11, 2002 8:26 AM
To: nlrs
Subject: [NLRS] Downconverters

Hello all,

I know this groups is more weak signal oriented but I
also know there are some satellite fans here as well. 
I'm in the process of building my station.  One of the
things I want to do work is satellites.  I notice some
people use radios capable of receiving 23cm and run
hardline from the antenna to the radio, while others
use a downconverter to bring the signal to a more
"cable" friendly region like 2 meters.  I realize some
do this out of need, ie: not having a receiver capable
of receiving at 23cm, or the antenna to radio distance
would induce to great of loss.

I could do either.  Intuition tells me that if I can
receive at 23cm, and the run to the antennas is
reasonable, not to use the downconverter.  Anytime you
insert something into the signal path you incur
losses, the case for the downconverter seems to be:
which loss is greater, the loss signal at 23cm due to
cable length or the loss of signal due to addition of
downconverter.

Is this sound thinking?

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