[Elecraft] Monitoring transmitted signal waveforms

[Don Wilhelm]

Paul,

You should be able to simply connect one of the vertical 'scope channel
inputs to the center conductor of your coax.  Be careful not to exceed the
peak voltage rating of the 'scope - 100 Watts with a 2:1 SWR will present
200 volts zero to peak - and the voltage increases as the square root of the
power.

I would recommend using a 10x 'scope probe (again look ath the voltage specs
for the probe) and connect that probe directly to the coax center conductor
(a coax Tee makes it easy).  The low capacity of the 10x probe will keep any
loading to a minimum (running coax direct to the 'scope input will work too,
but that kind of 'scope lead will act as a stub on your transmission line).
Don't forget to connect the ground side to the 'scope as well or you will
not obtain a meaningful display.

I usually only use the 'scope to observe the RF output when I am using a
dummy load, and I simply connect the 10x probe directly to the dummy load (I
have rigged a tie point just for that purpose).  If the voltage exceeds the
'scope probe rating, an attenuator can be used to bring the level down, but
you should not have to do that unless you are contemplating really high
power.

Now that you have a connection to the vertical channel, set the time base on
the 'scope to provide the waveform display that you wish to investigate.  A
fast sweep time will display the individual RF cycles while a slow display
(audio frequencies) will show you the modulation envelope (that is what you
are used to seeing on the Heath monitor).

Set the 'scope to trigger on the vertical channel that you have connected to
the RF source.

73,
Don W3FPR

----- Original Message ----- >
> I am hoping that someone can help me out with information on how to use an
> oscilloscope to monitor transmitted signal waveforms.  Many years ago I
had
> a Heathkit SB-610 monitor scope which allowed one to "see" the shape of a
> CW waveform and the little "Christmas trees" on SSB.  I could tell if I
had
> any key clicks on CW and if I was overdriving (flat topping) on SSB.
>
> I think there should be an easy way to do this with a regular
oscilloscope.
> But I don't know how to go about it.  I have a BK Precision 30MHz dual
> trace scope.  Any ideas will be most appreciated.  Thanks in advance.
>