Patrick,
The problem with your setup is that when you short across the input to the
receiver you can easily change the characteristics of the input circuitry
and the first RF amplifier.
Since the receiver was designed for ~50 ohms input, and you want to measure
the radio's output noise level under a no-signal condition, you will want to
terminate the input with 50 ohms.
Jim - KR9U
>>>Will someone please explain why what I'm about to write is not true (if
that is the case.) I'm trying to follow the "debate" regarding coax losses
and their effects on transmit and receive.
The receiver has an inherent internal noise floor which can be qualitatively
observed by shorting the input coax fitting and cranking the RF and AF gain
up. If the signal portion within the "signal + noise" coming through the
coax to the rcvr goes sufficiently low it will be irretrievably lost in the
receiver's internal noise irrespective of other considerations. Coax losses
on receive could in some weak signal situations attenuate the signal
sufficiently to reduce it below the rcvr internal noise and make it
unrecoverable.
Clearly, I'm no expert, just trying to understand the topic under
discussion. Critiquing the above could help me understand the matter
better.
Patrick NJ5G
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