On 29/05/17 02:16, Jeff Liebermann wrote:
On Sat, 27 May 2017 19:24:00 -0400, Michael Black
wrote:

I've certainly thought about buying one of those cheap ones, hoping I
could bypass the prescaler, though I suspect another issue, the prescaler
isn't a decade counter. Back when Heathkit came out with a frequency
counter, circa 1971, the prescalers were decade counters, and things got
better as they improved, and the frequency counters had higher limits.
But that sort of IC seems out of fashion now, so the prescalers are meant
for other things, and offer a binary division, so bypassing it in the
counter (and maybe adding an input stage) means the clock for the counter
is "wrong".
Michael

http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620

To get from 2400 MHz to 60 MHz requires dividing by 40. However, that
doesn't seem to be how this one works.

Checking the prescaler chip from the photos,
http://img.yunqudao.com/UploadFolder/4f2543ab-bfc8-48f0-9aff-c49e51612b75/Default/40_6.jpg
I find a Fujitsu MB501L prescaler:
http://pdf1.alldatasheet.com/datasheet-pdf/view/61659/FUJITSU/MB501L/+4155-UwSHHTTVdRhCtYT+/datasheet.pdf
That's a 64/65 or 128/129 prescaler for a dual modulous synthesizer. I
would guess(tm) that the eBay counter would use divide by 64 to get:
2400 / 64 = 37.5 MHz
which is too low to utilize the full 60 MHz counter range.

However, there's a problem. The MB501L prescaler is only rated to
1.1GHz. How they claim 2.4GHz will remain a mystery.

I assume the MB501 was 2c cheaper than the MB506 that the project
was designed with. Find one of the many versions that actually use
the MB506 instead.