[Elecraft] Keying Waveform Measurement

[W3FPR - Don Wilhelm]

Steve,

The setup pictured is IMHO overkill, but it covers all bases for any kind of
transmitter.  No doubt the ARRL Lab has a semi-permanent setup for this
test, but all that equipment may not be required depending on what you wish
to conclude from your test

The Keying Test Generator is nothing more than a keyer - but that one has a
special output for triggering the 'scope.  In most cases, the 'scope can be
triggered on the channel that the keyer output is connected to.

The setup shown requires a 'scope with a 50 ohm input to properly load the
attenuator.  Commonly available 'scopes have a high impedance input rather
than a 50 ohm input.  If the 'scope and probe input will accept the voltage
level presented by the transmitted signal, the attenuator may be replaced
with a dummy load (keeping the power output under the speced limit for the
'scope).  In fact if all you want to look at is the shape of the output
waveform, you only need one channel connected directly to the RF output (and
a dummy load)- just trigger on the input and display 2 or 3 dot times.

If you need to measure the relative timing of the RF envelope with respect
to the keying, a dual trace 'scope is needed.  Trigger the 'scope on the
channel connected to the keyer output (trigger on the negative going slope)
and you can read the delay from the onset of keying to the beginning of the
RF wavefront.

That is about all I can tell you other than those test setups shown will
work and can tell you all you need to know about the keying characteristics
of any transmitter.

73,
Don W3FPR



> -----Original Message-----
>
> I was wondering if anyone on the reflector has tried to observe a
> transmitted keying waveform using the technique described on page
> 25.50 of
> the 2005 ARRL Handbook, and depicted in Figures 25.86 and 25.87.
>
> The Handbook makes no mention of what the "Keying Test Generator"
> is or how
> to correctly set it up. I'd be most grateful if someone could
> explain what
> a "Keying Test Generator" really is.
>
> 73,
>
> Steve Kercel
> AA4AK
>
>