[RVRC] Great Explanation on using Squelch and RF Gain control

[Drew Moore]

.


    Re: SQL/RF-Gain knob
    <http://groups.yahoo.com/group/FT817/message/65420;_ylc=X3oDMTJyazhvdTU4BF9TAzk3MzU5NzE1BGdycElkAzIxNzA0OTgEZ3Jwc3BJZAMxNzA1MDYzMTA4BG1zZ0lkAzY1NDIwBHNlYwNkbXNnBHNsawN2bXNnBHN0aW1lAzEyNjA5NjI0NjI->



      Posted by: "CharlesC" cpcohen1945 at yahoo.com
      <mailto:cpcohen1945 at yahoo.com?Subject=%20Re%3A%20SQL%2FRF-Gain%20knob>
        cpcohen1945 <http://profiles.yahoo.com/cpcohen1945>


        Tue Dec 15, 2009 11:55 pm (PST)



Bill --

THANK YOU!

You've given the key information:

. . . Squelch is (mostly) useful when receiving FM signals;

. . . RF Gain is (mostly) useful when receiving SSB/CW signals.

The general rule for FM:

. . . Set the menu option for SQUELCH;

. . . Set the SQUELCH level _just high enough_ so that the radio is 
quiet when there's no signal coming in (for example, on an unused 
frequency close to the signal frequency).

The general rule for CW/SSB:

. . . Set the menu option for RF GAIN;

. . . Set the RF GAIN to maximum, and turn it down if you hear 
strong-signal distortion.

The order I use to reduce gain -- for strong CW/SSB signals -- is:

. . . turn on IPO (that turns off the RF amplifier);

. . . turn on ATT (that reduces the signal from the antenna by 20 dB);

. . . turn down RF Gain (that reduces the gain of the remaining IF 
amplifier stages).

The RF Gain control (it actually adjusts both RF gain _and_ IF gain) 
works by increasing the ALC voltage, as the RF Gain is turned down. The 
ALC voltage is what drives the S-meter. So as you turn down the RF Gain, 
the S-Meter reading increases.

This is confusing behavior, but it's standard across all the rigs I've used.

I don't know if what we've all written is easier to understand than 
what's in the manual. But I just read the manual, and it's clear as mud.

Charles VA7CPC

--- In FT817 at yahoogroups.com <mailto:FT817%40yahoogroups.com>, Bill 
McCourt - WF1L <wemccourt at .
.. wrote:

Here's my understanding of what each function is/does:

Squelch - This control sets a signal strength level/ threshold 
requirement that must be exceeded to un-mute the receiver.  Hence you 
only hear the "loud" 2M Repeaters, the less loud/strong repeater signals 
being "squelched" (not reproduced).  The "auto-squelch" applies a fixed 
threshold level to unmute the receiver where the squelch control allows 
an adjustable threshold level to be set. Used primarily in FM mode.

RF Gain - This control increases or decreases the amount of gain 
(amplification) accomplished in the RF amplifier stage of the 
receiver.  This raises or lowers the overall amount of amplification of 
the intended signal and background noise that is then injected into the 
frequency conversion sections of the receiver resulting in increasing or 
decreasing of the signal plus noise audio reproduction at the speaker.  
This control may be used to decrease the band noise that is received 
along with the signal.  After the RF gain is decreased, the audio gain 
control would then be increased to bring the reproduced signal, less the 
noise, audio level back to the desired listening level.  This is 
especially effective when listening for signals in the SSB, CW & AM modes.

AGC - Automatic Gain (volume) Control is a feedback type of circuit that 
regulates the level of a control bias applied, proportional to signal 
strength, so that the amount of RF or IF amplification is reduced on 
strong signals.  This capability is primarily used to maintain a 
constant volume/gain level regardless of incoming signal strength 
especially in phone reception.

Hope this helps you.

Bill-WF1L
Reston, VA

--- On Tue, 12/15/09, walscobry <walscobry at ...wrote: