[amsat-bb] Re: AMSAT Broadband Preamp Specs

Alan wa4sca at gmail.com
Thu Oct 3 13:26:54 PDT 2013


High Sierra Microwave has some small passband filters for the FUNcube dongle which might be of help:



Full disclosure.  I know the owner, N6GHZ though his work with AMSAT, but otherwise have no




<-----Original Message-----
<From: Paul Stoetzer [mailto:n8hm at arrl.net] 
<Sent: Thursday, October 03, 2013 11:02 AM
<Cc: Alan; amsat-bb at amsat.org
<Subject: Re: [amsat-bb] AMSAT Broadband Preamp Specs
<Thanks for the "real world" example. My receiver is an Icom IC-R10, 
<which the specifications say has a 0.25 uV sensitivity on 144 MHz and 
<0.32 uV on 435. I operate portable, so I'm not using the 
<preamp for the 
<high gain to overcome cable loss, but to overcome the relatively high 
<noise figure of the receiver. The preamp works great for FO-29. When I 
<have a clear horizon, I can hear it down to 1 degree or so 
<with an Arrow 
<antenna. My problem is the horizon (and a military spread spectrum 
<radiolocation system that causes "clicking" noises all over the 70cm 
<band here in Washington).
<On 2m, the preamp also helps greatly, but the preamp also amplifies 
<countless out of band signals that desense the receiver. I have a PAR 
<electronics notch filter to notch out the pagers at 152 MHz (two 
<kilowatt pager transmitters are a quarter mile away from me), but that 
<doesn't completely eliminate the problem. I have used a 10 dB 
<between the preamp and receiver which eliminates the desense, but also 
<reduces the signal level a bit too much. A 6 dB attenuator 
<should arrive 
<in my mailbox shortly and I'll try it on the next pass of AO-7 this 
<What I likely really need to add is some low loss bandpass 
<filtering for 
<2 meters, but it needs to be small since I operate with 
<everything in a 
<DSLR bag carried around my neck. Any suggestions?
<Ultimately the only perfect solution is a second FT-817 to use as the 
<receiver, but that's not in the cards at the moment.
<Paul, N8HM
<On 10/3/2013 11:22 AM, Alan wrote:
<> Paul,
<> Spence did some rough testing, but it was designed to be 
<simple, cheap, robust, and easily duplicated
<> rather than cutting edge.  I did some A/B testing with an 
<ARR preamp on SO-50 and FO-29.  Both made
<> significant improvement, and I did not hear any practical 
<difference.  That would not likely be the
<> case if we were talking about P3 bird at apogee.
<> 73s,
<> Alan
<> <-----Original Message-----
<> <From: amsat-bb-bounces at amsat.org
<> <[mailto:amsat-bb-bounces at amsat.org] On Behalf Of Paul Stoetzer
<> <Sent: Thursday, October 03, 2013 5:40 AM
<> <To: amsat-bb at amsat.org
<> <Subject: [amsat-bb] AMSAT Broadband Preamp Specs
<> <
<> <I was curious - has anyone measured the noise figure and gain of the
<> <AMSAT Broadband Preamp?
<> <
<> <73,
<> <
<> <Paul Stoetzer, N8HM
<> <Washington, DC
<> <_______________________________________________
<> <Sent via AMSAT-BB at amsat.org. Opinions expressed are those of
<> <the author.
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