hp 8640 signal generator

[n6wg]

I have a nice 8640, which is an excellent signal generator.
However, I'm interested in sweeping filters with it.
Does anyone know if there is a way to get it to sweep,
or are we stuck with manual tuning?
Thanks and 73
Bob N6WG
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[Jack Smith-6]

For narrow band sweeping (depends on the frequency range, couple hundred
KHz at max) you can use the 8620B's FM mode.

Put the sweep generator into the FM external input, and also onto the X
axis of your 'scope. Keep the modulating frequency low. Does not have to
be a linear ramp either, sine wave will work but you will have a bit of
a puzzle interpreting the oscilloscope x-axis in this case. If you keep
the sweep speed very slow, there are no significant FM sidebands, so you
have, in essence, a sweep. The 8620B is DC coupled on FM, so there's no
low limit to sweep speed.

Jack


Robert Tellefsen wrote:

> I have a nice 8640, which is an excellent signal generator.
> However, I'm interested in sweeping filters with it.
> Does anyone know if there is a way to get it to sweep,
> or are we stuck with manual tuning?
> Thanks and 73
> Bob N6WG
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
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>  

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[Jim Wiley-2]

Robert -


Try using a low-frequency AC signal, as from a function generator, and
DC couple it to the 8640B FM modulator input.  Depending on how much
sweep you need, I think this will work. I am pretty sure the 8640B FM
section will respond to DC.

If you have a function generator, and it generates sawtooth waves, you
can use the same signal to drive your scope.


Alternately, if you don't have a function generator, but do have a
fairly modern scope, then perhaps it has a "sweep out" signal (often on
the rear panel) that you could use to drive the 8640B FM section.  The
results would probably be the same.  Using DC coupling insures that low
frequency signals make it all the way through the amplifier chain in the
various instruments.


Other than not having retrace blanking, the results should look pretty
much like any sweep generator / detector combo.


- Jim, KL7CC



Robert Tellefsen wrote:

> I have a nice 8640, which is an excellent signal generator.
> However, I'm interested in sweeping filters with it.
> Does anyone know if there is a way to get it to sweep,
> or are we stuck with manual tuning?
> Thanks and 73
> Bob N6WG
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>
>  

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