Thanks, Alan.
I'm also on the FUNcube list and saw that link from a thread about this
very topic. I will likely give that a try at some point, though the
combination of 152 MHz notch filter, preamp, and 6 dB attenuator seemed
to do a very good job on the last pass of AO-7. I heard no evidence of
receiver desense, receive signal strength was still quite good, and I
copied the satellite quite well down to below 5 degrees to the north,
which is my worst direction. There is still quite a bit of noise, but
I'm afraid that's likely all broadband noise.
73,
Paul, N8HM
On 10/3/2013 4:26 PM, Alan wrote:
Paul,
High Sierra Microwave has some small passband filters for the FUNcube dongle
which might be of help:
http://hsmicrowave.com/FUNcube%20Dongle.html
http://hsmicrowave.com/Model146M2PBPF_101011.PDF
Full disclosure. I know the owner, N6GHZ though his work with AMSAT, but
otherwise have no
connection.
73s,
Alan
WA4SCA
<-----Original Message-----
<From: Paul Stoetzer [mailto:n...@arrl.net]
<Sent: Thursday, October 03, 2013 11:02 AM
<To: apbid...@mailaps.org
<Cc: Alan; amsat-bb@amsat.org
<Subject: Re: [amsat-bb] AMSAT Broadband Preamp Specs
<
<Alan,
<
<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
<attenuator
<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
<afternoon.
<
<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.
<
<73,
<
<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
<> WA4SCA
<>
<>
<>
<> <-----Original Message-----
<> <From: amsat-bb-boun...@amsat.org
<> <[mailto:amsat-bb-boun...@amsat.org] On Behalf Of Paul Stoetzer
<> <Sent: Thursday, October 03, 2013 5:40 AM
<> <To: amsat-bb@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@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
<> <
<>
<
_______________________________________________
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