[amsat-bb] Re: Receive Pre-Amps for 70cm

K5OE k5oe at aol.com
Tue Feb 7 04:46:02 PST 2012

An omni antenna with the current crop of LEO's is at the margin for an effective station.  A preamp will help substantially in two cases:  1) the antenna and radio are far enough apart the RF losses in the coax cable degrade the signal (and more importantly, the NF), or 2) your radio's front end is not very sensitive (more of a problem with "classic" rigs than today's offerings like your FT-8800).

To get the most out of your eggbeater(s), follow these guidelines:
 - put the best (lowest loss) coax you can between the antenna and the preamp
 - keep the coax between the antenna and the preamp as short as possible (use this criterion to determine whether you mount the preamp right at the antenna (preferable) or inside the attic using an indooor unit)
 - as suggested by Alan, use a 50 dB diplexer to split the signal to the V/U antennas
 - use a second diplexer (with the lowest insertion loss you can find) between UHF antenna and the preamp (UHF side only)
 - put as much physical separation as you can between the UHF and VHF antennas

Other useable preamps, besides those mentioned already by Peter and Alan, include Mirage, Landwehr, and even Icom.  I saw a pair of nice Mirage preamps go on ebay last week for less than $50 each.  If you do buy one that is not RF switched, you can power it or switch it (with a relay) driven by the FT-8800's data jack (usually pin 3 on late model Yaesu rigs).

Jerry, K5OE

--- original posting ---
I recently purchased an M2 Satellite Eggbeater antenna kit with the intention 
of working satellites from my shack.  I think this antenna will work best with 
a pre-amp for the 70cm band that perhaps I can put in my attic close to the 
antennas.  Who makes a good pre-amp for this situation to mate with my FT-8800 
radio.  Thanks, Peter     KC2RBX    

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