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Re: NF of transistor mixer ?



The noise figure will be at least 6 dB worse as a mixer than as an amplifier.
This is because the transistor is on only half the time. Since the operating
point as a mixer is usually not optimum for a low noise figure there is an
additional degradation. A reasonable estimate would be a 9 dB NF degradation.

73,

John
KD6OZH

----- Original Message -----
From: "William Leijenaar" <pe1rah@hotmail.com>
To: <amsat-bb@amsat.org>
Sent: Tuesday, 04 January, 2005 18:18 UTC
Subject: [amsat-bb] NF of transistor mixer ?


> Hi AMSATs,
>
> I have made here a UHF downconverter which has a transistor mixer in it.
> I want to make some NF measurements, but first I wanted to know how much the
> whole thing will give in theory (pre-amp + mixer + IF amp). However, I have
> no idea how much NF I can count for my transistor mixer...
>
> I have been looking for some literature about it, but I can not find
> anything concrete.
> The NF data of the transistor I have, but I am not sure if I just can take
> the NF out of the data-sheet...
>
> 73 de PE1RAH, William
> ---
>
> _________________________________________________________________
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----
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