[ARC5] Dumber than a rock....

[Jim Wiley]

Well, that may not work, depending on what IF you are sweeping.  The 
8640 series has a nominal low frequency limit of about 500 kHz, although 
most will go down to about 450 kHz.

A better solution is a down-converter that can take the signal generator 
output at say 50 MHz, and convert it to what amounts to zero to 10 
MHz.   There is a such a device, ready to go.  It is the Hewlett-Packard 
11710B Down Converter.  The 11710B takes a 50.0 MHz to 61.0 MHz signal 
from the 8640 and converts it to an output at 0.01 MHz (10 kHz) to 11 
MHz, retaining all the features of the 8640B, including the calibrated 
output and modulation. These units, while somewhat rare, are 
nevertheless available from vendors of used test equipment and at 
popular on-line auction sites.

While the factory made version is great (I have one)  a home-brew 
version is very practical, and a very useful addition to the workshop if 
you are working with signals  in the 50 kHz to 500 kHz range.

The 8640B will FM at least +/- 300 kHz at 50 MHz, which means the 500 
kHz output (after down conversion) gets you a sweep from about 200 kHz 
to 800 kHz, surely enough to sweep any IF stage that uses a center 
frequency in the 250 to 700 kHz range.   Obviously, narrower sweeps are 
possible too, as well as sweeps on other IF center frequencies.

If all you re interested in is an RF sweep, the conversion can be based 
on almost any "pivot" frequency that produces the desired output.

- Jim, KL7CC




On 5/24/2013 4:28 PM, J. Forster wrote:
> If you want more deviation, consider operating the 8640 at half of IF 
> and using a doubler: You can easily cobble up a doubler with a power 
> splitter and mixer. -John