On 29/05/17 02:43, Jeff Liebermann wrote:
On Sun, 28 May 2017 16:13:52 +1000, Clifford Heath
wrote:

On 28/05/17 14:25, Jeff Liebermann wrote:
On Sun, 28 May 2017 08:09:04 +1000, Clifford Heath
wrote:
On 28/05/17 04:35, Jeff Liebermann wrote:
On Sat, 27 May 2017 12:55:02 -0400, wrote:
Look for something that has a built in prescaler. Something like
this:
http://www.ebay.com/itm/Blue-RF-Signal-Frequency-Counter-Cymometer-Tester-0-1-60MHz-20MHz-2400MHZ/172396798620
I have two of those. I bought the second because I thought I'd
broken the first, it performed so badly. They're as bad as each
other.
Thanks. I was thinking of buying some of those. I should have known
as much of the low cost "modules" that I've purchased seem to have
deficiencies as a result of crude design or cost cutting exercises.

It was developed by a good hobbyist who posted everything online.

I couldn't find any such project. I suspect that it might have gone
the same way as the various M328 component test meters being sold
online. The original project was open source. It was then
commercialized by various vendors with wildly varying pricing.

Yes, that seems to describe it.

Google for Sanjian Studio (which is on the PCB) and you'll find
an English translation of the manual. That had assorted URLs to
www.hellocq.net where the many stages of this project's development
was discussed. You have to log in to see the schematics. I subscribed,
but my account seems to have now expired (I didn't get the spam that
I expected from this subscription). So I only have the assorted files
I downloaded, see he
https://www.dropbox.com/sh/z91pqvcpg470tuy/AAAIRnVfRDqrbrJwA3yBVQVPa?dl=0

I think that full schematics of slightly earlier versions are
available online. He uses a dual-gate MOSFET before the prescaler
and before the main counter, with the inputs paralleled. I think
that affects the sensitivity (though I don't have measurements)
so for my 2nd module, I cut a track to separate the input paths.

If the amplifier is used to simply produce a square wave out of
whatever it fed into the input, low gain might be a big problem. So
will noise around 0v which is why a "threshold" adjustment is usually
supplied.

Yes. High gain is a problem too, causing spurious transitions.

Something similar to a CATV or OTA TV/FM amplifier might be suitable.
However, don't worry about getting a flat frequency response. Just
take whatever you can get that produces enough drive to make the
MB501L prescaler happy.

Yes, except it's meant to be (and mine are) and MB506.

A collection of communications freq range
bandpass filters would be nice to prevent triggering on out of band
junk.

Good idea.

The main counter is a PIC.

Earlier schematics show two 4-bit counters before the PIC,
which by itself does not have a 60MHz counter.

Clifford Heath.