[amsat-bb] Exciting Coax

[Edward R Cole]

I guess I differ with Greg  KO6TH on what I consider "reasonable 
loss".  I do a lot of VHF thru mw frequencies and hate to loose more 
than 1-dB in loss.  I consider 25-foot of RG-213 at 144-MHz as max, 
then go to LMR-400 for longer runs (up to 150-foot).  If longer runs 
needed then I use LDF or equivalent hardline.

My 2m eme antennas are 214 foot from the PA and measured total loss 
is 1.67 dB, but my preamps are mounted on the tower and only see 
about 0.4 dB loss.  On 1296 my dish is about 100-foot from the shack 
and I have 6-dB loss in the LMR-600 transmission line.  Fortunately 
my high power PA's are located at the dish and only need 2w drive 
from my 20w transverter in the shack.  On 1296 receive the preamp is 
mounted directly to the dish feed and have about 125 foot of LMR-400 
to transverter (7-dB loss).  But preamp has 37-dB gain so easily 
overcomes the loss with about 30-dB residual gain to the transverter 
to result in 0.3 dBNF.  This is all for eme where losses will kill 
your ability so see weak signals.

73, Ed - KL7UW
   http://www.kl7uw.com
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