[R-390] Okay, don't laugh at me but...

[David Wise]

In the 8-16MHz range, the 8640B can only sweep +/- 80kHz, which
is not really wide enough to align a broadcast FM IF.

I can think of three ways around this.

1. Another VHF generator and a mixer.  Tune the 8640B to, say,
60.7 and the other gen to 50.  Drift will equal the second
generator's drift.  Another 8640B would be great.  You can get
by with a 608 if you warm it up beforehand.

2. An 11710B Down Converter.  Tune the 8640B to 60.7 .

3. Amplify the 8640B's 5MHz timebase and mix with 8640B output.
Tune the 8640B to 15.7 using underrun on the 16-32 range.
See Agilent App Note AN171-2, "Extending the 8640B Frequency
Down to DC".

Dave Wise 

>-----Original Message-----
>From: r-390-bounces at mailman.qth.net 
>[mailto:r-390-bounces at mailman.qth.net] On Behalf Of Barry
>Sent: Wednesday, March 09, 2011 1:46 PM
>To: r-390 at mailman.qth.net
>Subject: [R-390] Okay, don't laugh at me but...
>
>I am aligning an old FM radio and I want to sweep the IF 
>transformers but I don't have a sweep generator.  I know that 
>my function generators with VCO input can function as a sweep 
>generator, but they don't cover the 10.7MHz range.
>
>Here's the dumb question:  Can I use my HP-8640B (in FM mode) 
>and feed the modulation input with a triangle waveform from a 
>function generator to essentially cause the 8640 to sweep the 
>center frequency?
>