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RE: Coax Cable



Hi Jim, With considerable interest I read the reply from Ron W8GUS. I have
carried out extensive tests on my installations and compared figures of all
the various options. Recently Jerry, K5OE wrote of Down-converters and
Preamps.
I agree with his conclusions except in my case, with a fully modified Drake,
I
did not experience the lower output level and am currently using a DEM
13ULNA
directly connected to the dish feed and short (1 metre) run of RG8 to the
Drake
which is boom mounted.
On 23cm I have an IC-910H feeding via 13 metres of 9913 to an 18 turn helix.
I
looked at rerunning the coax with LMR-400 but the advantage of only about
0.15dB
did not seem to justify the cost - about $180. I do have some Andrews Heliax
to
use as part of the run hopefully gaining a useful 1dB.

Back to basics. Seems silly to spend huge $$ for little (if any) advantage.
On
receive the losses must be kept to a minimum until the gain stages. It's
easier
to mount the Pre-amp directly to the antenna connector and run a few feet of
coax to the downconverter. Having used various coax runs from the pre-amp to
the
converter I can say that the quality used is of little importance however it
is
better to use a lower loss type (RG8 or RG6) than standard RG58. Again, this
assumes the downconverter is mounted close to the pre-amplifier. (I use RG58
for
the run from downconverter to the PCR-1000)

On the transmit side - it depends on what you use for a transmitter. The
IC910H
is only just sufficient for good 23cm uplink but on 70cm it has tons of
power.
Here I use RG8 to an 8 el yagi with excellent results. For me, losses are
not so
important having excess power available. Perhaps not most efficient but
certainly
effective.

Finally, if you already have the 9913, use it - it works just fine! It
sounds like
you have your 2.4GHz receiver in the shack - I think you'll find it more
economical
to buy a surplus unit (California Amplifier or even the Norsat 2500) than to
purchase
new LMR-400 and all the connectors.

-----Original Message-----
From: owner-AMSAT-BB@AMSAT.Org [mailto:owner-AMSAT-BB@AMSAT.Org]On
Behalf Of Jim Bennett
Sent: Wednesday, 10 October 2001 03:23 PM
To: AMSAT
Subject: [amsat-bb] Coax Cable


Been off the air for awhile.  Haven't kept up with the lastest discussion on
what coax everyone is using.  My satelite station has been off the air for
awhile and I need to move it to the garage.  I have been told to replace the
9913 coax that I was using with, RG-214 from the pre-amp to the antennas and
LMR-400 from the shack to the pre-amp.  Any comments would be appreciated.
Thanks in advance.

73s Jim KE4KOL, 30841

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