I've had several DSP receivers...Fist the Pegasus then TS-870 and TS-2000. I
believe QST mentioned key clicks in the receiver of the IC-756pro. Their
comment was something like....We noticed key clicks when tuned just outside
of the passband of strong cw signals. Upon checking, we found that the key
clicks were actually there and not DSP artifacts. etc etc.
The question then becomes: How come I don't hear all those clicks on
receivers with normal crystal filters? Here's one explanation.
With DSP IF, I can crank the bandwidth down to 50hz. Now let's tune our RX
to within 200hz of a strong cw signal. You will hear strong clicks. Why?
Because they are there. That's why. No matter how clean his TX is, there's
still clicks when you tune that close. The DSP filtered out his CW tone/note
but not his clicks.
So now we need to know if what we hear is really the guys clicks or is it
something to do with all that digital processing and it's inability to snuff
out anything but audio tones or how it produces it's own clicks while trying
to process those fast clicks.
Since we don't have 50hz crystal filters it's hard to compare them with DSP
but if you have a normal xtal filted rig, try setting you filter at 250hz
and tune just outside of where you hear his tone and you should hear the
same clicks.
What DSP needs now is a click filter!
Steve
N4LQ
----- Original Message -----
From: "Barry N1EU" <n1eu@yahoo.com>
To: <tentec@contesting.com>
Sent: Tuesday, November 26, 2002 2:57 PM
Subject: [TenTec] CW Key Clicks and Filters
> W8JI deserves a lot of credit for drawing attention to
> this serious problem. Clicks are a function of the
> rise and fall time of the trasmitted waveform, and
> should therefore be independent of keying speed.
>
> I have to take exception to W4BQF: "I seriously doubt
> that there were very many contest stations generating
> key clicks during the contest as most contesters are
> pretty knowledgeable technically."
>
> I don't know which contest is being referred to, but
> key clicks were rampant on the bands in CQ WW and
> they're caused by poor transmitter design, and not
> poor operators or poor receivers. Some rcvr filters
> can emphasize the clicks, but if the clicks are being
> transmitted you're going to receive them.
>
> 73,
>
> Barry N1EU
> www.albany.net/~bg
>
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