I think the prescaler for my 5221A would be a waste of time. With only 4 digits and no over range indicator, there's no way to
tell what the actual frequency is. When 1MHz is applied all I get is the rightmost digit showing a zero.
I think my unit may have seen use as an event counter of some sort. When the switch is in "OPEN" position, it counts up until 9999 then goes back to zero.
Not a big deal for me and the 5221A won't see a lot of use unless I can add two more digits in future. It's more of a show and tell item.
It works as a frequency counter in a limited capacity.
However, I will breadboard a prescaler then hand draw a pc board if you want one. It's not a complicated piece of hardware.
I have close to 100 RCA CA3179 1.25GHz prescaler IC's. The only drawback is that they divide the VHF signal by 64 and the UHF by 256.
The timebase of the counter would have to be modified to see the true frequency. A one or ten Hertz timebase would show the input signal
as the result of the input frequency divided by 64 or 256. That's why I never used any of them.
700MHz would show 10937500 on the counter.
A calculator would give you the proper result 109375 X 64 = 700,000,000
If I was making a kit, I would toss in a dollar store $2 calculator as an "Auxillary Display Device"...
Getting ahead of myself here.