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Re: TranSystem AIDC - Another noise story



Now the measurements are starting to make sense.

Pieter

----- Original Message -----
From: "wc0y" <wc0y@email.msn.com>
To: <amsat-bb@AMSAT.Org>
Sent: Tuesday, May 22, 2001 21:45
Subject: [amsat-bb] TranSystem AIDC - Another noise story


> Another email about TranSystem converter noise figure!
>
> I did take some more measurements and came up with a new modification
since
> this topic is of such interest.  Thanks go to Mark, N0NSV, for sending me
> his TranSystem converter to work with.  He will get it back working much
> better.
>
> I used a sensitivity measurement method with a signal source and spectrum
> analyzer with Noise Marker capability.  The advantage is that I did not
have
> to guess at how to account for the noise contribution from the image
> frequency... it is included in the measurement.  The HP8970A noise figure
> meter does not automatically account for the image contribution.
>
> The results, in a nutshell, are as follows:
>
> With no mods => 9.8 dB NF !!
> With stub removed => 4.1 dB NF (123 and 145 MHz IF)
> With stub retuned to image frequency => 1.8 dB NF
>
> I retuned the stub to notch the 2111 MHz image frequency by soldering a
> 0.5pf chip capacitor on the open end of the stub, shifting its frequency.
>
> Details can be found at http://communities.msn.com/wc0y
>
> 73,
> Ward - WC0Y
>
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