[GreenKeys] frequency counter

[Gary Chatters]

On Fri, 17 Oct 2003,  wrote:

>  I wish to soon buy a frequency counter to help set up several diffrent
> Hal ST-5's and ST-6's.It seems that in watching ebay there are dozens of
> diffrent counters for sale such as 80mz, 512mz, ect.Exactly what should
> I be looking for? I have never used a counter before, but think it would
> also be nice to have so I can tell where my Heath HX-10 is set to and I
> never know where I am on my Swan 500cWayne WB0CTE
>

There is no way to tell you "exactly" what to look for, but we can go over
some of the possibilities.  And there are a lot of variations.

Upper frequency capability.  If you only want to use it for audio and HF
you won't have much trouble finding something.  There may be a few audio
or low frequency counters, so you still need to check this.  Higher
frequencies are more of a problem.  Some older counters might have a limit
at 50MHz or 80MHz.  Some will have an optional prescaler to go to 500MHz
or more.

Sensitivity.  As another poster mentioned, be sure it is good enough.
Triggering at volt or fraction of a volt is typical.  You may get down to
1 or 10 mv.

Direct vs. reciprocal.  Direct counters just count the number of cycles in
a given time period.  If you set the gate time for 1 second, the precision
will be limited to +-1 Hz.  Reciprocal counters measure the time for a
whole number of cycles, then compute the frequency.  They are usually
rated in digits per second precision.  They are better for getting
accurate readings at low frequencies.  These are higher end counters.

Accuracy.  The accuracy of the reading is only as good as the timebase.
For audio and some HF work this won't be critical.  Decide what you need
and check the specs.

RF immunity.  Some cheap counters will be affected by external RF fields.
This is a consideration if you will be using it near a transmit antenna.

Frequency vs. universal.  Some frequency counters only do that: count
frequency.  Others are specified as universal counters.  These do other
timing measurements such as period, time interval, time interval average,
etc.

Physical considerations.  The HP-5245L is a great counter.  I used one in
the last FMT.  It is cheap and you can get plug-ins to extend its 50MHz
upper limit as far as 12GHz or its sensitivty to 1mv.  It also takes up 5"
of rack space, weighs about 40lb and has a really roaring fan.  Or you can
get a cheap little hand held thing that weighs a pound and runs on
batteries.

The problem with using a counter on a receiver or tranmitter is that the
oscillator frequency is not the same as the operating frequency.  Take a
look at www.aade.com.  This company sells frequency displays that can be
set to take account of the offset.

That's a start.  Maybe some others can help.  Join the test-equipment list
for more discussion about any kind of test equipment.

Gary