> I found it difficult to analyze the waveforms while trying to maintain
> sync - maybe a storage scope would have made things easier, but don't
> have access to one of those.
Here's a quick method to synchronize the monitored RF envelope on the scope
to keep from having to chase the waveform:
Most transceivers and external keyers utilize a pull-up resistor to circuit
Vcc at the paddle/key jack. When the paddle, straight key or external keyer
activates, the key line is grounded. As such, a "Y" adapter can be used to
sample this point to the scope's external trigger port or second scope
channel when using a multi-trace scope. The scope can be set to trigger
upon a FALL of voltage sensed either at the external trigger port or scope
input. Precise waveform measurements can be made as well as measurement of
propagation delay through the transmitter. In other words, one can easily
measure the time from "key down" to the onset RF just like that shown in the
QST Product Reviews. In addition to key click measurements, this gives a
good idea as to potential QSK performance.
I take this concept a step further and have modified my external keyer with
a positive going RCA jack. So, as I send repeated keyed elements, each one
can be seen on the scope. On some transceivers, the first keyed element
will behave differently than successive elements (e.g., ALC power spikes,
"dit shortening," etc.). Transceivers that are well-timed and have smart
ALC systems show identical keying envelopes from the first keyed element in
a series through the last.
Paul, W9AC
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