[GreenKeys] RTTY receiver noise immunity?

[Ralph Mowery]

Most FM receivers operate on what might be called supersonic noise.  There is a filter that passes noise after the detector that is above normal speech or music frequencies.  When the FM receiver picks up a signal this noise reduces. So the voltage is reduced and the squelch circuit activates on loosing this noise. The filter keeps the speech and music frequencies from passing.

Most AM  squelch operates off the automatic volume control circuit and is depending on the strength of the signal.

Ralph  ku4pt


-----Original Message-----
From: greenkeys-bounces at mailman.qth.net [mailto:greenkeys-bounces at mailman.qth.net] On Behalf Of Richard Knoppow
Sent: Tuesday, April 20, 2021 12:51 PM
To: greenkeys at mailman.qth.net
Subject: Re: [GreenKeys] RTTY receiver noise immunity?

    I am far from an expert at this but it seems to me that the 
situation is analogous, actually the same, as an FM receiver. As 
long as the signal is above a threshold, called "quieting", there 
is no noise output. Audio receivers also have a "squelch" to mute 
the receiver when the input signal is below a set threshold. I 
don't know if this would be applicable to FSK for RTTY