Great post, Jim. Thanks!
Based on what I learned doing that study several years ago of ARRL Lab
data, I completely agree. There are other things we can do as well.
After I gave a preliminary version of that study to someone who I
strongly suspected would pass it along to Yaesu, whose radios were the
worst offenders, a firmware upgrade for that series of radios was
released that improved keying to the extent that it looked more like the
second worst offender (of that generation), ICOM. :) If you have one of
those rigs, by all means install the upgrade. I did before and after
measurements of keying bandwidth on a neighbor's FTDX500. They are here.
http://k9yc.com/P3_Spectrum_Measurements.pdf
The study of ARRL Lab data is here.
http://k9yc.com/TXNoise.pdf
Yes, the slowest possible rise time should be used when it can be
adjusted. The reason no adjustment is needed (or possible) with Elecraft
rigs (beginning with the K3) is that the keying waveform is carefully
shaped for maximum clarity and minimum clicks. Flex adopted this a year
or so after ARRL Labs first tested the 6500 series. I don't know if
they've tested those rigs for keying bandwidth after that upgrade.
Another major generator of clicks (and splatter) is the use of ALC
between the transceiver and the power amp to control power. In general,
that form of ALC should ONLY be used to protect the amp from faults in
the antenna system, including the operator transmitting into the wrong
antenna. :)
I haven't studied the current generation of Yaesu rigs on CW, but the
lower cost models generate terrible splatter -- typically 2 kHz or more
on both sides of their intended bandwidth, only 20 dB down. That is, 2
kHz on the suppressed side of the carrier, and 4-5 kHz on the other side
of suppressed carrier. I discovered this when helping a neighbor figure
out why his new Yaesu was splattering, also by observing it on other
signals, alerting the splattering station, who told me what rig he was
using.
Obviously, if the transceiver is generating the splatter (or the
clicks), the power amp will amplify it (and maybe add more of its own).
Think about it -- if someone with one of these rigs is 30dB over S9 in
your receiver, his sidebands will be 10 dB over S9, not great if you're
trying to work someone on an adjacent frequency.
Yes, there were some very clicky signals this weekend. Thankfully fewer,
as Elecraft and Flex rigs continue to proliferate.
73, Jim K9YC
On 11/12/2020 9:23 AM, Jim McCook wrote:
Anyone who has been operating in CW contests is aware of the rampant key
click problem we all must deal with.
If you are using a JA made radio, please check the CW rise time to be
sure it's set to 8ms (unless 6ms is maximum... which needs to be
changed). Also check to be sure you're not hot switching your
amplifier. Key clicks in contests have become a serious problem and
it's long overdue for resolution. If you use an older JA radio without
that adjustment, there may be a key click mod that will eliminate those
clicks.
There is a reported case of a radio set for 8ms being sent to the
manufacturer for repair and was returned with a 4ms setting. Please
check after such repair returns.
Elecraft and Flex users need not be concerned unless something is wrong
with the radio.
73, Jim
W6YA
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