Paul, The main advantage of a preamp is increasing your sensitivity by lowering the noise figure of your receiving system. You lose some of that by locating the preamp in the shack. Any coax loss between the preamp and antenna adds directly to the overall NF: 80-foot of LMR-400 is 1.2 dB loss and added to a 0.5 dB NF preamp nets you a system NF = 1.2+0.5 = 1.7 dB.
But it will still increase the sensitivity of most radios that have NF in the 6 to 12 dB range. Recently I lost one of my eme preamps on my tower and used a preamp at the shack. My normal system NF = 0.76 dB. In the shack I had 0.25 + 1.7 dB cable loss = 1.95 dB NF. That lowered my sensitivity by about 5 dB but I still received eme signals. I would suggest you make a comparison for yourself. Try the preamp in the shack and try it near the antenna and see how much that affects your receiving ability. It is not hard to enclose a preamp inside a plastic box for outside use (a small sandwich box works). 73, Ed - KL7UW At 08:36 PM 3/13/2011, Paul Delaney - K6HR wrote: >Does anyone have their preamps in the shack as opposed to mast mount? >Any major disadvantage to having the preamps in the shack? >I just acquired two AR2 SPxxxVDG preamps and understand they are not >weatherproof and would need an enclosure to mount near antennas, which for >the time being is not possible. Any thoughts would be appreciated. > >Paul Delaney - K6HR >paul.hamra...@verizon.net >http://k6hr.dyndns.org:8080 > > >_______________________________________________ >Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. >Not an AMSAT-NA member? Join now to support the amateur satellite program! >Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb 73, Ed - KL7UW, WD2XSH/45 ====================================== BP40IQ 500 KHz - 10-GHz www.kl7uw.com EME: 144-1.4kw, 432-100w, 1296-testing*, 3400-winter? DUBUS Magazine USA Rep dubus...@hotmail.com ====================================== _______________________________________________ Sent via AMSAT-BB@amsat.org. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
