Philips-Fluke PM6665 Frequency Counter with Oven Controlled Crystal Oscillator

Wed, 23 Dec 2015 00:00:00 +0000

Upgrading a Philips-Fluke PM6665 Frequency Counter with an Oven Controlled Crystal Oscillator - Up and Running!

I needed a frequency counter for my little lab at home. Naturally, I wanted an HP Agilent 53132A or similar, but it’s way too expensive for my modest use. So I browsed around eBay and found an old Philips-Fluke PM6665 frequency counter with the optional 1.3GHz add-on board. With a 10 second gate time, I can get down to 0.1 Hz at 10 MHz, so that’s more than I need. It didn’t have the option of a better crystal, unfortunately. When I tested the PM6665 against my Trimble 10 MHz GPSDO reference, the unit was off by 200.1 Hz. Without a calibration sticker on the instrument, I’d say that’s pretty good for a device manufactured in the late 80s. I tried to trim it, but it uses an adjustable capacitor, and you only needed to look at it for it to change settings.

Upgrading a Philips/Fluke PM6665 Frequency Counter with an Oven Controlled Crystal Oscillator OCXO

Thu, 19 Nov 2015 00:00:00 +0000

I’ve finished the OCXO upgrade. Read about it here

While browsing on eBay for my new lab at home (I’m getting into electronics again), I came across a Philips PM6665 Frequency Counter, an old but functional unit so I couldn’t resist, I had to buy it. So I downloaded the Users Manual and Service Manual for the frequency counter and started to check the schematic. As usual the unit, when new, could be bought with several options. One of them was a better crystal oscillator, an MTCXO that can be automatically calibrated using a 10 MHz external reference, giving an accuracy of 3*10-8 but my unit doesn’t have that option, unfortunately. This will be fixed though. But it does have a 70 MHz to 1.3 GHz optional input!

So here’s what I plan to do…

Ocxo on Jackenhack

Philips-Fluke PM6665 Frequency Counter with Oven Controlled Crystal Oscillator

Upgrading a Philips-Fluke PM6665 Frequency Counter with an Oven Controlled Crystal Oscillator - Up and Running!

Upgrading a Philips/Fluke PM6665 Frequency Counter with an Oven Controlled Crystal Oscillator OCXO