Re: [Repeater-Builder] UHF Preamplifier

[Kevin Custer]

Think about this for a minute, if the noise level increased, the squelch circuit would have seen MORE noise and rammed the squelch closed. What actually happened is, adding a better device in front of the receiver lowered the receivers total noise figure, decreasing the noise in the squelch circuit, requiring the squelch pot to be set tighter. Very common effect. Common? Must be another explanation, as you're talking apples & oranges here w.r.t. noise. Remember this is FM, so more noise power at the front end doesn't mean more noise at the discriminator unless the limiter isn't being driven into limiting, which is probably what's happening. But adding a preamp can only add total noise power, never subtract. Bob NO6B If what you are saying is correct, adding the preamplifier should have placed a receiver lacking in overall gain into full (or at least more) limiting.  If so, this would have raised the noise level to the discriminator, thus tightening the squelch.  He commented that he needed to set the squelch pot tighter, which means there was less noise present after the installation of the preamp.  Maybe I didn't explain it well, but I have seen this effect before, even on the bench where extraneous signals quieting the receiver can be ruled out. Kevin YAHOO! GROUPS LINKS  Visit your group "Repeater-Builder" on the web.    To unsubscribe from this group, send an email to:  [EMAIL PROTECTED]    Your use of Yahoo! Groups is subject to the Yahoo! Terms of Service.