[R-390] HP-606* vs URM-25*?

[David Wise]

> From: Roy Morgan [mailto:roy.morgan at nist.gov]

snip

> I don't have one [8640] yet, but I understand that the prices are 
> coming down 
> steadily on this one.  The 8640 will do about all you ever 
> need a signal 
> generator for. Except be repairable if you blow out the 
> output solid state 
> hybrid module by transmitting into it with a transceiver.

I got mine at eBay for around $250 less shipping.  It was
partly operational and missing a couple of knobs.  I was
able to replace them with generic ones from RS with some
judicious drilling and gluing.  (Thank goodness the original
skirt was still there!)  I felt that the Band and FM Deviation
had too much detent.  It's easy to soften it; they use multiple
leaf springs, just take a couple out.

I don't know if it's endemic, but it had several cracked
nylon gears and plastic switchplates.  I was able to repair
them, but those little contact fingers are hard to keep
track of when they fall out.  I glued them back on with epoxy.

Option 001 is a variable-frequency modulation source, very handy.
You may be spot it in a photo, look for a viewing window
in the second knob from the left.

Option 002 extends the frequency to 1024MHz.

Option 003 is reverse power protection to 50W.
These have a stick-on label above the RF Out connector.

Option 004 is an extra-precise step attenuator and modulation cal.
The single big rotary dial at the right is
replaced by two smaller ones sort of side by side.

Dave Wise