[amsat-bb] Coaxial line question

Luc Leblanc lucleblanc6 at videotron.ca
Sun Jan 24 02:04:21 PST 2010

Yes again a returning question "preamp at the tower or near the shack"

I will have to do soon some maintenance work on my satellite antennas tower. I planned to use 2 heliax 1/78" 45'  individual line. Each 
line will be terminated by high quality 2psp coaxial microwave switch feeding UHF and VHF antennas. I don't know if i can move my VHF and 
UHF preamp at the other end near the shack where each line will enter the house on short LMR 400 run 10 feet max?

I know the theory says the best place to put a preamp is at the antenna but with the very low loss on the Heliax coaxial line,  is in the 
real world there will be any significant degradation in the noise figures who will be really noticeable?

Note: If the relays are introducing too much loss i can feed the antenna directly from them on the 8' run on LMR-400 directly on the female 
N type heliax connector.

P.S. One commercial microwave technician is telling me that i will be able to see difference only on labs spectrum/signal generator in 
short i will be unable to tell any difference due to the short length of my coaxial line. He told me he's playing with 300 to 600 feets of 
lines in his day to day work and 45 feet heliax run are nearly consider as jumper line in his world... 


Luc Leblanc VE2DWE
Skype VE2DWE


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