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More Bang for You Buck - RF Cafe Forums

The original RF Cafe Forums were shut down in late 2012 due to maintenance issues. Original posts:

Amateur Radio | Antennas | Circuits & Components | Systems | Test & Measurement


mfurman
 Post subject: More Bang for you Buck
Posted: Mon Sep 12, 2005 4:15 pm 
 
Lieutenant

Joined: Mon Sep 12, 2005 4:02 pm
Posts: 3
Location: Washington DC
Hi all,
I'm interested in combining the inputs of an S-band signal from two 1-meter antennas. I was hoping to use separate LNAs at each antenna, then provide an IF delay line that could compensate so that the indivdual antenna feeds could be summed PRIOR to modem input. Can something like this be done to effectively enhance the G/T or am I smokin something?
Michael
:shock:


 
   
 
kanling
 Post subject:
Posted: Mon Sep 12, 2005 5:47 pm 
 
Colonel
User avatar

Joined: Mon Jul 18, 2005 4:31 pm
Posts: 32
Location: Baltimore, MD
My first reaction was "Gasp, the signals won't be in perfect phase!" Then I saw you already planned for the delay line to bring them together.

I guess the only thing preventing it would be the delay stability of the LNAs. If the delay line is fixed, any delay drift in the LNAs would mess everything up. You'd have to check with the LNA mfr, I guess.

But actually, I don't think you would gain anything because I think the SNR of the signal is basically set by the noise floor of the LNA. Summing two LNAs together would give you the noise floor of whichever one is highest.






Posted  11/12/2012

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