[CQ-Contest] Fwd: [FCG] riding the RF gain...

Eric Scace eric at k3na.org
Wed Dec 5 17:58:36 EST 2001

   One can thing of your inner ear as another device in the chain between antenna and brain.  The inner ear has a dynamic range,
just like a radio receiver, with a minimum discernible signal (different at different frequencies), a level at which ear-generated
distortion occurs that generates false perceived noise and obscures weaker signals, and a maximum tolerable power level.

   For best reception by the ear, one wants the radio receiver's audio output range (from the headphones) to be properly positioned
within the useful dynamic range of the inner ear.  The receiver's minimum discernible signal (just around the receiver's noise
floor) should be set to the ear's minimum discernible signal level -- in other words, the receiver gains are set so that empty band
noise (or the lowest signal you want to detect in the ear) is just barely audible to the ear.  This gives the greatest possible
range of useful volumes for the ear.

   Unfortunately, many operators forget that noise in the shack (amplifier fans, computer fans, etc) add to whatever the receiver is
applying to the ear.  When the shack is noisy, the operator just turns up the receiver gain controls to compensate.  But that just
reduces the available dynamic range that the ear has to work with.

   One improvement is to first provide the ear with a quiet listening environment before the radio is turned on.  To test this out
in your own station, turn on all your usual contesting equipment, put on your headphones, but don't plug the headphones into the
receiver.  Just sit there with dead headphones and notice how much other "stuff" you can hear.  Start to work on eliminating this
background QRN.  You might relocate some hardware with noisy fans or use headphones with better all-encompassing earmuffs (even
aeronautical-grade headphones made to shut out engine noise), for example.  I have also reduced the background QRN by using ear
plugs (another 10 dB of noise reduction) as a last step.

   The ultimate noise floor in the ears is blood circulation noise.  When you put on the headphones (with no equipment attached) and
the audio world just goes dead (and if your hearing hasn't been damaged by age or abuse), then you can hear the soft rushing sound
of the circulation noise floor.  Now plug in to the receiver, and adjust the receiver gain at a quiet spot of the band so that the
receiver's noise floor is just detectable.   You now have about 100 dB of dynamic range (audio) to play with.  If you operate with
the AGC off, and the AF gain set so that the band noise at a quiet frequency is just barely detectable, there is quite a lot of
headroom to play around with before a received signal hits the non-linear or pain thresholds of the ear.

   -- Eric K3NA

-----Original Message-----
From: owner-cq-contest at contesting.com
[mailto:owner-cq-contest at contesting.com]On Behalf Of Georgek5kg at aol.com
Sent: 2001 December 3 Mon 15:59
To: CQ-Contest at contesting.com
Subject: [CQ-Contest] Fwd: [FCG] riding the RF gain...


In recent years, I have learned to use the radio with the AGC turned off.  I
have learned that many old time cw ops have used this technique for years.  I
don't always do it, but find it useful in some types of condx.  If I am
working a weak pileup, I find that it works really well in distinguishing one
signal from another.  Of course, strong stations calling on the freq will
blast your ears; a real problem forcing the need to ride the RF gain control.

A trick that Dean, N6BV, told me about is to keep the audio gain as low as
possible.  It helps to differientiate one weak sig from another.  In doing
multi-ops with other operators, I find that they generally run the audio gain
too high, IMHO.  I try to keep the audio cranked down to where the sigs are
barely hearable.

Something that I have come across in the past year that I really like is the
binaural cw feature in the Timewave 599zx.  This is a subtle feature that
tends to put the high tones in the right ear and the low tones in the left
ear.  This gives a depth to the cw signals and in a strange way seems to give
a separation of the tones in the brain.  I can't explain it any better than
that, other than to say that I find it pleasant and a help in the pileups.

73, George

George I. Wagner, K5KG
914-312-9460 fax

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