[CQ-Contest] Click, click, click...

Tom Rauch W8JI at contesting.com
Fri Feb 23 20:25:35 EST 2001

Hi Dick and all,

If this is too long, skip to the end. I have a constructive suggestion
that might be fun and educational.

 > I think it's more likely that the MP receiver can't handle lots of
 > strong signals in the wide passband of the early stages. This could be
 > true of other "state-of-the-art" radios, too. Up until this weekend,

Most radios fall apart somewhat at close spacing. The ARRL
announced on the topband reflector they will now publish close-
spaced specs in reviews, rather than the wider spaced tests that
mask many defects. If you look at the topband archives, you'll find
a list of some receivers tested at close spacing.

That cheap little Elecraft kit was better than most high-dollar

Adding less than $1 worth of parts I significantly improved the close-
spaced performance of my FT-1000D.

It seems design-care rather than cost is behind less than state-of-
the-art performance.

 > my run radio was an MP and I was often bothered by clicks. In ARRL DX
 > CW, I did most of my running on an FT-1000D. I hardly noticed clicks
 > unless they were coming from very loud stations right next to me (the
 > stock Yaesu 500Hz filters don't have the steepest skirts in the
 > world.)

I'm certain some of it can be in the receivers, but certainly not all of

I can dump 100 milliwatts into my two diode-mixer modified R4C's
before they begin to gain compress, and they still get clicked to
death from some signals that are 0.01 milliwatts or much less.

One way to tell without a high DR receiver is to attenuate the signal
to reasonable levels and see how wide it sounds. If the clicks
suddenly vanish or drop at a higher rate than the attenuation, it is a
receiver problem.

 > As for amps causing clicks or a "wide" signal, I guess I need a
 > technical refresher -- how does an unmodulated carried become
 > non-linear, compressed or flat-topped? My understanding is that

The slope of the rise and fall times control the bandwidth, IF the rig
is not FM'ing. If the rig is FM'ing, it can be wide even if the rise and
fall times are good and the envelope looks perfectly flat on a carrier!
I suspect that's what some rigs do, because I can make my 751A's
do that by dicking with the R/T delay pot inside the rig. If I shorten
the R/T delay pot (to get faster QSK), I can make a click that
covers 100 kHz and the rig looks perfect on a scope! That's
because the VCO is still settling while the rig is transmitting.

The amplifier can change the rise and fall times, if it is hot-
switching. But it would have to be grossly non-linear to add clicks
from non-linearity. You'd likely arc the bandswitch over before that
happened. Amplifier defects are most likely from relays closing
while RF is applied.

 > backing off the loading helps improve the linearity of SSB signals,
 > but has nothing to do with CW. If the transmitter is causing CW
 > clicks, then its signal must not meet minimum standards for spectral
 > purity. I doubt that's the case with the MP or the amp.

The last I knew, and I have no reason to think it has suddenly
changed, HF transceivers require no emissions bandwidth
certification at all. They are not type-accepted. There are
equipment guidelines, but no signoff that it meets state-of-the-art
performance for in-band emissions.

If I build a super-regenerative receiver, I have to certify the
emissions. If I build 10,000 200 watt output amateur transceivers, I
only have to be sure the receiver and microprocessor's don't cause
problems under part 15. I should also check for harmonics and
spurious products unrelated to modulation, but they never ask for
that data.

I can build an amplifier that splatters like crazy, and it will pass
FCC TA as long as harmonics (and spurious emissions) are within
spec when measured with an unmodulated carrier at full power. It
will sail right through TA, and I don't have to fib about anything on
the paperwork. The only thing I've ever had them check is
performance on CB. One-half dB gain on CB, and they will flunk it.
Splatter up the wazooo, and it won't affect type-acceptance.

All the performance issues that affect us are left for us to handle
between ourselves, and we quit giving honest reports years ago.
We don't even have good OO's who meet technical standards
anymore. It's no wonder we have radios that are 30 dB worse for
IMD than some rigs from the 60's.

Maybe we need a Dayton forum on radios, and some test gear to
measure them. Wouldn't that be fun? A radio shootout with real
equipment grabbed at random from stations? Click click click
73, Tom
(W8JI at akorn.net) 

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