On Mon, 06 Nov 2006 19:51:47 -0500, Mike Coslo
wrote:

Roy Lewallen wrote:
Over 30 years ago I designed and built something similar to what you're
describing. I ran the CW signal through a sharp audio filter, detected
it with a diode, and used that to key an audio oscillator (rather than
amplifying the original signal as you describe). It was interesting, but
worked only for a rock-solid signal which was simple to copy anyway. It
didn't take much QRN or QRM to cut holes in the output signal which made
copy impossible.

The brain is an amazing signal processing mechanism. It's really hard to
beat. If I had a hearing disability, I'd look into various amplifying
and frequency shaping devices and perhaps some types of audio signal
processing. But in my opinion it's best to send more-or-less the
original signal to the brain and let it do what it's good at.

Hi Roy,

So much depends on the nature of the hearing problem. I have a lot of
holes in my hearing, as well as a different tone of tinnitus in both
ears. It took me over 6 months/3 hours per day to learn CW to 5 wpm. And
it still had to be crystal clear signal.

I learned a lot of things during this time. The main thing is that my
brain gives equal weight to all sounds, whether the CW I am trying to
copy, or whatever happens to be around it. Turns out that the same is
true for multiple people speaking, or one person speaking with an air
conditioner on in the room. This is probably related to the length of
time that I have been hard of hearing (started at 7 with a bad case of
the mumps, then the tinnitus started at 18)

If that's
not feasible, then use a digital mode that's specifically designed for
easy detection with electronic circuits and let them do all the work.

Yup, I'm a big fan of PSK31.

- 73 de Mike KB3EIA -

Hi Roy and Mike,

Ten Tec made a device similar to the one Roy is describing back in
the 1970's. It was called the S-20 Signalizer and I don't think that
Ten Tec sold very many. I still have mine and use it quite
frequently. As Roy said, it was not for weak signal work and most
everyone who bought one seemed to think it was just another filter or
Q-multiplier that would help dig out weak signals.

On the contrary, the Signalizer works best when you have a strong
signal and you just want to get rid of some annoying background sound,
like a heterodyne or static crashes. I use mine primarily on 80
meters when there is QRN and I feed its audio to one side of my
stereo headphones. The other side of the headphones goes directly to
the audio from the receiver so I can hear the raw signal without any
AGC action. The advantage of this arrangement is that I can turn the
receiver audio down a bit lower than I usually would and still pick up
those characters that I would miss completely with the signalizer. It
is definitely more comfortable than listening to the raw receiver
audio for a long period of time when QRN is present.

Of course, the above arrangement only works because the brain is in
fact "an amazing signal processing system", and can selectively insert
the weaker signal from the raw receiver audio into the stream of
perfect audio coming from the Signalizer.

Mike, I might add that the product review of the Signalizer in QST
said that the effect of turning it on was "like closing the door" to
shut out the noise from an adjacent room. When I try to describe the
effect of the Signalizer to others ("Its a re-keyer, not a filter"), I
often use the very analogy that you mentioned, namely that its like
being able to lower your voice when someone turns the air conditioner
off or other people stop speaking in a crowded room.

You occasionally see a signalizer on e-bay, often misdescribed as a
CW filter or amplified speaker. A couple of months ago one went for
about fifty dollars as I recall.

-- Dave WB4JTT