Uploaded March 2025 | Updated September 2026, 2 weeks ago

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In preparation for some upcoming atomic clock metrology, we repair two HP 5087A distribution amplifiers, an instrument so good it was in the catalog from 1972 to at least 1999. As luck would have it, one of them holds a surprise card that's not documented anywhere. We reverse engineer it, and find that it is quite useful.

SCSkits 5 to 10 MHz doubler card (HP 05087-60011 replacement): ebay.com/itm/155570308255

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- Support us on Patreon: patreon.com/curiousmarc
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"Elevator Music" Credit: Crinoline Dreams by Kevin MacLeod

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