I would like to apologise to anybody whose contacts and enjoyment of the
band have been disrupted by my clicks.
I thought I was being very smart by using the low level TX/RX connection to
my IC-765 rather than the relay, and by including a pulse stretcher so that
the amp would always be on longer than the TX. Unfortunately, I got a few
things wrong!
(a) I managed to make a pulse shortener rather than stretcher, and when I
tested it my nimble mind worked out that as the PTT was shorter than the
keying that was OK.
(b) The TX/RX output from the IC-765 leads the keying envelope by some 15ms,
and has vanished before the element is completely sent. In conjunction with
my pulse shortener this meant that the amp was in cut-off for both start and
finish of the element. (The amp changeover relays were not being
hot-switched, which might have alerted me earlier, but cut-off bias was
being removed too late and applied too soon.)
(c) The IC-765 keying relay is actually delayed from the low level control
and had I used that, things would have been better although not perfect.
I had a couple of complaints of clicks and looked at the signal on a
spectrum analyser. Whilst this showed sidebands, the clicks appeared to be
at a lower level than the phase noise, and I concluded this was OK. I also
asked several local stations to monitor my signal and they said it sounded
OK. So I did nothing for a while. Clearly, I was interpreting the analyser
incorrectly, and the locals were being too nice to me.
I think that all is now OK. If anybody thinks otherwise, I would be grateful
if they could contact me by e-mail (ve3zi@hotmail.com). There are a few
(hmmmm) other stations with pretty clicky signals. I would be delighted to
share my (new and improved) circuitry with them!
Once again, apologies.
73 Roger
VE3ZI
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