[Elecraft] K3 and preamp

[Fred Jensen]

Uhmmm ... Given the domain of David's email address, he's probably 
right.  However ... between doing other things while in SE Asia in the 
mid-60's, my team and I occasionally made it onto one of the larger 
bases for a week or so.  I usually made a trip to the MARS station to 
get a long-overdue "radio fix," and ran a few phone patches for the troops.

At most of the stations, there were a couple of homebrew sound-deadened 
phone booths with a telephone just outside the radio room.  Even when 
conditions were really good, it was fairly common for a wife to not 
understand her husband, sitting about 3 meters from me, however, she had 
no problem understanding me.  They had run a number of tests locally and 
the telephone input to the KWM-2A's sounded just like the mic on the air.

I finally concluded that there were two factors at work:  First off, he 
didn't sound like her husband, but she had never heard me except on the 
radio so I was understandable.  Second, and maybe more important, even 
with good conditions, there was inevitable HF noise, and she was 
listening to the noise instead of the weird voice purporting to be her 
husband.

As a result of the "other things," I came home quite deaf and I run the 
AF gain right at the distortion point in the headphones [my hearing aids 
don't work under the phones].  T-storm static crashes cover weak CW 
signals for me, possibly because they drive the cans into distortion. 
Steady noise -- grass on the P3 baseline -- causes me no problems.  I've 
never managed to get much benefit out of the K3 APF, likely due to pilot 
error.

I do know that our hearing mechanism is very complex.

73,

Fred K6DGW
- Northern California Contest Club
- CU in the 2014 Cal QSO Party 4-5 Oct 2014
- www.cqp.org

On 9/5/2014 5:14 AM, Brian wrote:
> Quite some time ago there was a discussion that adding a preamp at the
> K3 antenna terminals couldn't possibly help.  The argument is that it
> can't improve S/N
>
> Perhaps here is the reason it does help from somebody versed in
> ear/brain signal processing.
>
> 73 de Brian/K3KO
> --------------------
> On 8/28/2014 17:45, David McClain dbm at refined-audiometrics.com
> [FMT-nuts] wrote:
>  > Some weeks ago I was musing about the way we all listen to the weak
> ones on the HF bands.... And then it struck me, based on what I know
> about our hearing:
>  >
>  > While we all dislike the constant rush of noise in the headphones, it
> actually turns out to be helpful, and that's why we instinctively turn
> up the volume and just live with the noise. When you do that, you are
> imposing strong ambient noise on your hearing. That in turn affects the
> way your hearing works. It produces a much steeper response to weak
> signals riding in the noise. So a very small change in signal level
> causes a much larger change in apparent loudness in your brain. It makes
> it easier to read the weak signals.
>  >
>  > Coupled with that, we also need that noise to produce something
> called "stochastic resonance", which is the basis for dithered noise
> added to recordings. It lets you hear things that are solidly below the
> noise floor.
>  >
>  > - 73 de Dave, N7AIG