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

[Mike]

Hi Eric,

I just picked up a David Clark H10-40 Aeronautical Grade
Headset off of Ebay. Its amazing how much noise attenuation
these provide as compared to regular headphones. David
Clark actually publishes the noise attenuation specs (in dB
versus frequency) for their products.

http://www.davidclark.com/

Thanks go to Marty, N6VI for turning me on to these.

73 de Mike, W4EF..................

----- Original Message -----
From: "Eric Scace" <eric at k3na.org>
To: <Georgek5kg at aol.com>; <CQ-Contest at contesting.com>
Sent: Wednesday, December 05, 2001 6:58 AM
Subject: RE: [CQ-Contest] Fwd: [FCG] riding the RF gain...


>
>    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...
>
> Art,
>
> 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
> 941-312-9450
> 914-312-9460 fax
>
>
> --
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> Administrative requests: cq-contest-REQUEST at contesting.com
>


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