|From:||Marcus D. Leech|
|Subject:||Re: [Discuss-gnuradio] Question about TV-RX|
|Date:||Wed, 31 Mar 2010 11:33:03 -0400|
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On 03/31/2010 03:59 AM, Li Mei-Wen wrote:
Hi:The "sensitivity" of a receiver depends on a few factors, so it's hard to give a meaningful answer.
The tuner module (MT4937) has a noise figure of about 8-10dB, which will be the dominant contributor
But the "sensitivity" depends heavily on what type of signal you're trying to detect/demodulate, etc.
In FM radio, for example, "sensitivity" is often quoted in terms of the minimum signal level (usually
in microvolts) that is required to produce an audio output signal that is of acceptable quality, or that
has a certain minimum SNR (Signal-to-Noise Ratio).
Some types of signals are more "noise robust" than others. Standard AM signals, for example, are
notoriously non-robust, so they require less-noisy signals (more power received at the input of the
receiver) to produce equivalently-acceptable audio output.
Narrowband digital modulation schemes with built-in forward-error-correction are much more
noise tolerant, and so can operate acceptably well with smaller signals available at the antenna
You should be able to use the quoted noise figure of the MT4937 (used on the TVRX) of 8-10dB to work
out the sensitivity levels for your application. If an 8-10dB noise figure produces unacceptable results
in your application, then placing a low-noise-amplifier (less than 2dB noise figure) ahead of the TVRX
will vastly improve your results.
-- Marcus Leech Principal Investigator Shirleys Bay Radio Astronomy Consortium http://www.sbrac.org
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