[amsat-bb] Re: AMSAT Broadband Preamp Specs

[Paul Stoetzer]

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:n8hm at arrl.net]
> <Sent: Thursday, October 03, 2013 11:02 AM
> <To: APBIDDLE at MAILAPS.ORG
> <Cc: Alan; amsat-bb at 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-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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> <> <satellite program!
> <> <Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
> <> <
> <>
> <
>