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Re: DEM preamp and mods



Hi Russ,

I am planning on using this arrangement exactly as you mentioned. I am
already using it on my homebrew converter to receive AO-40 and it works
really well. I can hear AO-40 on a one square inch patch right above the
noise at apogee. Today I was able to do some preliminary noise figure
measurements using a noise source and a spectrum analyzer. It was a pretty
quick measurement so I don't have the exact numbers, but the NF is less than
one dB and the gain is 25dB with the ElectroMavin filter inline. I took a
JPG plot out of the HP network analyzer with the filter inline. Here is the
plot:

http://ozoni.com/n4ip/dem+era2+filter.jpg

This plot is the DEM preamp followed by an ERA2 followed by the ElectroMavin
filter

The gain at 2401 is around 25 dB and the image rejection is close to 72 dB
down from the desired which is really good.

My current converter that uses this arrangement is found here:

http://ozoni.com/n4ip/DSCN0485.JPG

I will post more detailed NF measurements when I get them.

Pieter Ibelings
N4IP


----- Original Message -----
From: "Russ Renaud" <ae517@freenet.carleton.ca>
To: <elpieter@hotmail.com>
Sent: Tuesday, May 22, 2001 11:48 AM
Subject: Re: [amsat-bb] DEM preamp and mods


> Thanks for posting the pic.  I planning to order this preamp kit, and
> will probably steal your idea for the ERA-2 to provide a matched output
> for the PHEMT amp, and run the Electro-Mavin filter between the preamp
> and the Drake 2880.
>
> Let us know your measurements when you have them.
>
> In what sort of box will you be mounting the preamp?
>
> 73


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