Accurate frequency measurements without a frequency counter

[MrSlack]

My circa 1975 frequency counter just blew up leaving me a smoking unobtainium IC and no frequency measurement ability. Boo hiss. I've drafted up a schematic for a new one, fullt discrete based on 74hc390+4511+other bits I floating around. Unfortunately I've got to wait 3-5 days for the bits to arrive and then a couple of evenings to throw it together.

After some reflection, this made me think about the times before ubiquitous digital logic and precise crystals. This begs the question: how did people accurately measure frequency back then?

[dannyf]

A charge-pump would do. Basically, if you add the same amount of charges to a charge-storage device (a capacitor for example), you get high voltage across it when the charge frequency is controlled by your input signal.

A small RC circuit, a capacitor + a gate would do.

[DimitriP]

Before "frequency counters" , there was this:
https://en.wikipedia.org/wiki/Absorption_wavemeter

[AF6LJ]

https://www.google.com/?gws_rd=ssl#q=heterodyne%20frequency%20meter
These were the Go-To frequency meters of the 20s-60s.

[MrSlack]

Thank you very much everyone. Lots of interesting reading ahead!

[IconicPCB]

Look for transfer oscillator approach..probably similar to heterodyne approach

Use a comb generator and a mixer.. look for adjacent comb lines make at whihc a beat tone is observed and solve for frequency of incoming signal

[barry14]

There were also analog frequency meters such as the General Radio 1142 which not only measured frequency but acted as a frequency discriminator (FM detector).  It operated by generated a fixed amplitude, fixed duration pulse for each zero crossing of the input signal.  Then these pulses were averaged and the result fed to an analog voltmeter.  Hewlett-Packard also made a similar unit.