2GHz..12GHz PLL / Prescaler / Synthesizer / Controller

On offer is one used (actually removed from new equipment), working synthesizer board designed for controlling an oscillator (originally a YIG, but potentially any VCO) in the range 2GHz..12GHz, together with a machined metal cover and connectors. Great for ham bands from 13cm to 3cm (2.4GHz ... 10GHz). Actually the range should be more like 500MHz.. 12GHz based on the specs of the chips, but I have not exercised them down that far.

The photo shows one of my spare boards, with SMAs and housing removed. The one on offer here is still intact and sealed with tape as it was removed from a new chassis.

The board contains a 12GHz divide-by-4 prescaler chip and front end multistage MMIC amplifier, so would also make a great input for a sensitive microwave frequency counter (or standalone prescaler) even without an oscillator. The prescaler on this board may be a Conexant/Rockwell RI41404, or Agilent/UMC chip or equivalent as in the documentation below. All are direct pin compatible chips, and I have not taken off the housing to check which.

This is followed by a NatSemi synth chip LMX2326 which can be driven from a PC using NatSemis free Codeloader software, or from your favorite microcontroller. The reference is an onboard 10 MHz VCTCXO. Synth control lines and TCXO control/output are brought out to the 20-way connector so interfacing is convenient.

The PCB is a thin double sided substrate, probably Duroid, and all components are on the same side with no hidden inner layers, making modification easy.

John Miles, KE5FX has also been pursuing this thread and has a page which describes his results and software at http://www.thegleam.com/ke5fx/stellex.htm. He has also (very conveniently) posted all the documentation including schematics and code in a single zipped bundle at: http://www.thegleam.com/ke5fx/stellex/stellex.zip. His code drives the synth directly from the PC parallel port with 4 wires.

If you are tempted to give this a go, I'd suggest that downloading the ZIP file (7.7Mb) and poring over the schematics would be a good first step. The interface to a PC is easy to knock up in an hour or so on perfboard or similar.

If you do not have a YIG to control, you might want to modify it to drive a VCO, such as the ROS-2150V or Agilent VTO-8200 I often list. This would give a range of 1..2 GHz or 2GHz..3GHz, and would mean you could use the prescaler/amplifier portion in another project (by feeding the VCO signal directly to the synthesizer). For VCO control the PLL output amplifier would need to be modified to produce a voltage rather than the current which controls a YIG, details in the synth data sheet.

The board is usually covered with a machined housing (included), and includes two female SMA connectors and the 20-way 0.1" dual ended header (all included in the auction) so it's easily connected with a standard 20-way IDC ribon cable without soldering.

A great article about Microwave Synths in general, authored by Ulrich Rohde is on the web at: http://www.synergymwave.com/Articles/PDF/Synthesizers.pdf

There's some useful Atmel AVR control code for LMX23xx synths at dl5neg's site , at http://www.dl5neg.de/rf_wf_generator/MIXER_LO/Mixer_lo.asm (as well as some really nice projects, worth a look).

Overall a nice little Synth unit for the RF experimenter! I've had a lot of fun/success with these boards and thought I'd share my spares ..

Price Reference

I expect these would have been rather expensive originally ... even a 12GHz prescaler assembly will normally run over $100 ...

About RFPlus

RFPlus is now well settled in to his cosy nook down here in Cornwall - and with the Postal Strike averted (Ya-hay!!!) it's time to start on some new listings. I've discovered several boxes from previous projects, most parts now being surplus to my needs, and with the ever present need for cashflow it's time to liberate them here on Ebay. Listing always takes me a fair bit of time (so they'll appear slowly over the coming weeks) but if you've an interest in RF items, particularly Microwave frequency parts, then please check back because there are some real goodies coming up.

In the meanwhile, I'll relist some items of which I still have a few and hope you'll find them interesting!

For other info, visit my the 'About Me' page. If you're thinking of bidding/buying I'd ask that you visit that page at least once so you can read the 'Terms & Conditions' and a bit more about RFPlus.

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