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Re: Preamp for a Mobile Application




On Mar 31, 2008, at 8:01 AM, Bill Dzurilla wrote:
> Kent,
>
> Never tried it, but I doubt a preamp would be worth
> the expense if mounted at the rig in a mobil set-up.
> I assume the feedline is only 10' or so.  The preamp
> helps most when the feedline is lengthy, especially if
> cheap coax is used.


Agreed with all of Bill's comments, snipped to save space.

The "dollars to dBs" value proposition for pre-amps in a mobile  
installation with short coax runs doesn't work out until after you  
have an incredibly large antenna system.

A higher gain antenna and a way to point it "buys" you a lot more  
signal at the receiver, and is probably cheaper -- up to a point.  It  
also helps you out on transmit, so you get "double-duty" out of  
antenna system upgrades.

(One can always look at some of the papers from organizations like the  
Southeastern VHF Society, from weak signal VHF terrestrial  
enthusiasts, especially "rover" stations in this particular case to  
see the math to engineer the "best" system one can for mobile weak- 
signal operations, since that's all Satellite work really is... weak- 
signal operating with a need to point the antenna more critically and  
more often, in both a horizontal and vertical plane, and different  
operating techniques.  At the end of the day, other than Doppler  
shift, the RF physics are the same.)

--
Nate Duehr, WY0X
nate@natetech.com



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