Fluke/Philips PM66xx Frequency Counter OCXO Upgrade

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https://www.electronics-lab.com/flukephilips-pm66xx-frequency-counter-ocxo-upgrade/

In this post Dan Watson documents an OCXO upgrade board he designed for the Fluke/Philips PM66xx line of frequency counters. A few months ago I purchased a Philips PM6674 frequency counter on eBay. It’s an older 9 digit counter with two channels that has a maximum input frequency of 550MHz. The design feels dated compared […]

Fluke PM6608B Frequency Counter 10MHz OCXO Reference Upgrade Module

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https://www.electronics-lab.com/fluke-pm6608b-frequency-counter-10mhz-ocxo-reference-upgrade-module/

Fluke PM6608B Frequency Counter 10MHz OCXO Reference Upgrade Module – [Link]