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VK2ZRG > TECH 07.04.06 08:08l 31 Lines 1041 Bytes #999 (0) @ WW
BID : 2347_VK2ZRG
Read: DL1LCA GUEST
Subj: Noise figure query
Path: DB0FHN<DB0NOE<DB0GAP<DB0AAB<F6KFT<LX0PAC<ON0LGE<DB0LJ<DB0RES<ON0RET<
ON0DXC<ED1ZAC<EA5RQ<VK7AX<VK2TGB<VK2IO<VK2WI
Sent: 060407/0244Z @:VK2WI.#SYD.NSW.AUS.OC #:11023 [SYDNEY] FBB7 $:2347_VK2ZRG
From: VK2ZRG@VK2WI.#SYD.NSW.AUS.OC
To : TECH@WW
VK2ZRG/TPK 1.83d Msg #:2347 Date:07-04-06 Time:2:45Z
Hello all,
I am writing a programme that, amongst other things, calculates an
overall noise figure of three cascaded amplifiers, with provision for
having a loss component in front of each stage. The first loss would
be that between the antenna and the receiver (or pre-amp) input for
example.
Assuming you have a perfect receiver of zero dB noise figure with a
loss of 3 dB between the receiver and an antenna (whose effective
temperature is 290 Kelvins), my query is this :-
If I cool the input loss to zero Kelvins so that the 3 dB loss no longer
generates any noise, does the 3 dB loss reduce the noise coming from the
antenna? (I know that it's not possible to get to absolute zero, but let's
pretend that you can.)
I think the system temperature reduces to 145 K ...what do you think.
73s from Ralph VK2ZRG@VK2WI.#SYD.NSW.AUS.OC
Taglines by Colin Coker G4FCN
C Program run, C Program Crash...ReWrite in Pascal!
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