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

Marijan Miletic, S56A artinian at siol.net
Wed Dec 5 15:35:27 EST 2001

Beware of many hearing problems caused by headphones!  I know few good CW
op's who suffer from ringing or deafs caused by Q multipliers.  Late G3FXB
was the prominent case...  I only got 25 dB notch at 3 kHz and I used
speaker in my early days.

Fortunately any RX can handle up to 50 dB of audio on HF and you may stay on
the safe side.

73 de Mario, S56A, N1YU
  ----- Original Message -----
  From: Eric Scace
  To: Georgek5kg at aol.com ; CQ-Contest at contesting.com
  Sent: Wednesday, December 05, 2001 2:58 PM
  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...


  In recent years, I have learned to use the radio with the AGC turned off.
  have learned that many old time cw ops have used this technique for years.
  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
  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

  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
  too high, IMHO.  I try to keep the audio cranked down to where the sigs
  barely hearable.

  Something that I have come across in the past year that I really like is
  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
  a separation of the tones in the brain.  I can't explain it any better
  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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