On Sat, 15 Mar 2008 05:14:53 -0700, ltdoc wrote:

Bill,
That's one of those "sort of" kind of questions. It depends a lot
on the particular receiver and what frequency range you plan to listen
to, and then on the amount of space you have for an antenna.
In general, receivers that listen to the lower frequency bands, HF
for example, are more sensitive than those that are used for the higher
bands (VHF, UHF, SHF).

More correctly, it's _easier_ to make an HF receiver with a good noise
figure, and harder to do so as the frequency goes up.

However, atmospheric noise goes _down_ as the frequency goes up. So for
weak-signal work a receiver designer has a lot of motivation to make
really quiet front ends on VHF and higher equipment. Basically if the
radio is cheap (i.e. if it's for consumer use) then the front end may as
well be made of wood. If the radio is used for long-distance
communication (i.e. microwave links, space communication, some military
or amateur radio) then designers will go to great lengths to get the
noise figure down.

-- snip --


--
Tim Wescott
Control systems and communications consulting
http://www.wescottdesign.com

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"Applied Control Theory for Embedded Systems" by Tim Wescott
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