[Moon-net] additional cable loss in front of LNA

[Charlie Kahwagi]

Almost  right........

With LNA of 0.5dB  and  Cable loss of 0.6dB Ahead of preamp  AND SWR 1:1
Then  NF  =  1.1dB  (0.5 + 0.6)

With SWR 7:1    and additional cable loss = 1.3dB (from table) than  NF = 
2.4dB  (0.5 + 0.6 +1.3)

Either way  your Noise Floor has increased by 1.3dB!
(Solution: Ask your QSO partner to increase power by 1.3dB  HiHi!)

73
Charlie
VK3NX

----- Original Message ----- 
From: "Koellner, Guenter (NSN - DE/Muenich)" <guenter.koellner at nsn.com>
To: "ext Bodo Heyl" <bodoheyl at gmx.de>; "moonbounceboard" 
<moon-net at list-serv.davidv.net>
Sent: Thursday, May 08, 2008 10:37 PM
Subject: Re: [Moon-net] additional cable loss in front of LNA


Yes, I assume it is correct

-----Ursprüngliche Nachricht-----
Von: moon-net-bounces at list-serv.davidv.net 
[mailto:moon-net-bounces at list-serv.davidv.net] Im Auftrag von ext Bodo Heyl
Gesendet: 08 May 2008 14:30
An: moonbounceboard
Betreff: [Moon-net] additional cable loss in front of LNA

Lunatics,

my question:
There are in antenna books and elsewhere
tables showing the additional cable loss in respect
to cable loss and SWR ratio.

Lets take following case:
My LNA is situated a few meters behind my
perfectly (nearly) matched antenna. The SWR of
the LNA is about 7:1 (return loss ca. 2-3dB) which
is highly common with MGF1302 preamps.
The loss of the cable between antenna and LNA
is 0,6dB.
According to a.m. table my additional cable loss would be
ca. 1,3dB.
Since any loss in front of the LNA must be added
to the noise figure, the NF will be finally instead of
lets say 0,5dB
then 0,5dB plus 1,3dB = 1,8dB.. Is this right???

Reply by the experts (to moon-net)
would be appreciated!

73 de Bodo/DL2FCN




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