On 19 Oct 2005 05:26:32 -0700, "RHF"
wrote:


+ AGC set "Off"

* Global : 122W24 Longitude by 37N78 Latitude

Why no AGC?

David Asks - " Why 'no' AGC ? "

REF - Deutsche Welle (DW) News Link on 690 kHz in English
via CBU in Vancouver, BC = http://tinyurl.com/9s4pv

WHY "NO" AGC ? - - - Why Turn the AGC "Off" ?
http://groups.yahoo.com/group/Shortw...a/message/5914

Sometimes with a very weak signal on the Coax Cable {Shielded}
Loop Antenna where the S-Meter reads a Flat "0" {Zero} with
Fair Audio (No Pre-Amps)

It has been my experience that 'sometimes' by Turning "Off"
the AGC the Listenability of the Radio (RF) Signal will show
improvement with very weak signals. YMMV !

Hence the SIO Code : 3.4.3

S = Signal Strength = Fair for the Consistant Strength
of the Signal not the S-Meter Reading.

I = Interference from other stations like local SF Bay Area
Sports Talk Radio on 680 kHz.
KNBR AM 680 kHz = http://www.knbr.com/

O = Overall Quality = Fair

More about KNBR AM Sports Talk Radio 680 kHz :

FCC Clear Channel 680 A,B,D KNBR @ 50 KW {Unlimited}
San Francisco, CA: Class A (I-B)
http://www.fcc.gov/mb/audio/amclasses.html
http://www.csgnetwork.com/amclearradiotable.html

KNBR @ 50 KW uses a single "ND1" Non-Directional Antenna
http://www.fcc.gov/fcc-bin/amq?list=0&facid=35208

KNBR @ 50 KW is about 25 Miles due South of My QTH.
KNBR TX MAP = http://tinyurl.com/8n4dh

SF Bay Area Radio Stations - presented by TV Radio World
http://www.tvradioworld.com/region1/...ters.asp?m=sfr

SF Bay Area Radio Digest = http://www.bayarearadio.org/blog/

HELLO EVERYONE - So Am I Doing Something Wrong ? - Comments ?

QUESTION - Is Turning "Off" the AGC a valid Listening Technique
when Listening to Weak Radio Signals ? ? ?


hope this helps - iwtk ~ RHF

RHF wrote:
Why Turn the AGC "Off" ?
http://groups.yahoo.com/group/Shortw...a/message/5946

Howdy RHF,

The AGC is typically (though not always) driven by the signal level in
the IF. Strong signals that are slightly off the listening frequency
can leak into the AGC enough to cut the gain even though you don't
hear them. Thus a nearby strong signal or even noise can reduce
receiver sensitivity when you're listening to another, weaker signal.

The same effect can cause 'pumping' of the AGC, when a signal is
either internmittant (like CW) or undergoing rapid fading - the
receiver sensitivity bounces up and down with the interfering signal.

AGC time-constants can sometimes be exactly wrong for the fading
cycle of a signal - it reduces gain just as the signal itself is
fading.
This is why it's nice to have a choice of time-constants - slow and
fast for example. When listening to sideband or CW, having a slow ACG
helps smooth out the inrush of noise in between sylables, words, etc.

Try turning off your AGC more often, if only to get an appreciation of
how much work it's generally doing. You'll be amazed at how much more
variable signal levels are than you ever thought.

- Robert [VA2ERY]


Good post. The Icom R-75 has selectable no AGC/slow AGC/fast AGC,
and each is very useful at different times for different conditions.

Tony

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TM - tyvm ~ RHF

But "Robert [VA2ERY]" wrote it; all I did was re-post it here.

DX Ace,

I tried the trick with backing-off on the RF Gain and with
the Icom IC-R75 Receiver; when you do the S-Meter slowly
starts to creep-up the scale.

Hey, but it does work and you can "Hear" a difference in
the RF Signal.

once again thanks for the tip ~ RHF

dxAce wrote:
Meanwhile... you're just plain annoying, 'tard boy.

http://www.iserv.net/~n8kdv/pics.htm

nice shack ace...


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