Mixer as freuency doubler

There's a guy on the HP/Agilent groups that makes and sells brass gear replacements.

Thanks, but have you seen the prices? This is from another vendor, done in aluminum: $99/ea. There were also some resin gears and someone selling a plastic 3D printer version that probably will not last. I've seen others in the $30 price range.

I made a crude drawing and sent it out for bid to a local machine shop. It came back at about $20/ea in quantities of 50. Each HP8640B requires 2 gears. I doubled the price and asked some likely customers for money up front. None were interested, so I abandoned the gear cloning experiment.

It's not that difficult to repair a cracked gear. I've posted instructions (somewhere) and received generally positive email on the results. All it takes is a round file and some decent epoxy mix. Anyone able to extract the gear assembly from the generator should certainly be able to do the gear repair.

The difficult part is aligning the switch sections so that everything is in sync. The most common screwups are accidentally filling the set screw hole with epoxy and/or having one of the tiny contact fingers fall off the switch rotor.

Unless you have Option 2. You get the full 1024MHz, plus a bit.

Mine are Option 2.

Yep. That's why I said "basic HP8640b". They're quite common on eBay. Mine is Opt 1,2, and 3.

List of options plagerized from the manual:

- Option 001 provides a modulation oscillator that is continuously adjustable from 20 Hz to 600 kHz. The oscillator can also be set for

- Option 002 provides an internal, active frequency doubler that extends the frequency range of the generator to 1024 MHz (to 1100 MHz with over range).

- Option 003 protects the generator output circuits from accidental applications of reverse power up to 50 W.

- Option 004 provides a demodulated output and modified AM circuitry for setting very accurate AM depths. It also has a 1 dB output step attenuator in addition to the standard 10 dB output step attenuator.

- Option H66 which includes option 001 provides an additional control for very fine adjustment of the output level and improved harmonic content in the RF output signal.

- Option 323 is the military version in a portable carrying case.

So are mine. The option 3 isn't very much needed, in my case.

That's aimed at VOR/ILS, IIRC.

I wouldn't want to carry one very far :-)

I need it. I work with transmitters and accidents do happen. I even bought an HP8640B for parts, just to extract the Option 003 hardward and retrofit one for a customer. A fuse works, but isn't always fast enough.

Nope. Option 004 is intended for avionics. H66 is designed for precision intermod testing where the spurious harmonics would cause too much clutter on the spectrum analyzer screen. The shop I previously owned a piece of had an HP8640B, but it was just too big and heavy to use for ramp checks. So, it sat in the shop. The real work was done with various IFR/Aeroflex (IFR 1200s, 1500) service monitors, which could also be used to check the transmitters.

I was referring to Option 4, I just inserted the comment in the wrong place.