The HP 5381A uses a Mostek MK5009 timing
generator and it operates at 1 MHz. It has a crystal
oscillator amplifier internally and this is used by
HP as the basic timebase. There is a pin made
to receive an external 1 MHz clock which is made
for TTL. The input on the 5381A is coupled directly
to the MK5009, wide open for all kinds of problems.
This should not require a lot of engineering to
interface it to the TB output. A 10 MHz input capable
of seeing the TB output followed by any of a number
of off of the shelf dividers. I would try a divide by 5
followed by a divide by 2 to drive the input of the 5009.
Bandwidth is an issue for these old PMOS parts.
Greg
On 3/24/2011 12:10 PM, Bruce Griffiths wrote:
James Fournier wrote:
My intention is to divide the signal by 10 and feed it as an external
frequency reference into my old HP counter. Hopefully this will increase
it's stability.
As for the circuits i have tried, there have been so many. Most of
them are
variations of each other as i experimented on a breadboard. However,
a few
examples are the inverter and diff. amp. circuits from the wenzel
site. The
inverter (4049) produced a small .1vpp sine wave. The amp produced
another
sine wave of of basically the same magnitude as the input. I also
replaced
the inverter with a buffer (4050) and Schmidt trigger buffer. The buffer
produced the same result as the inverter and the Schmidt produced no
output.
I tried some small signal diodes, can't remember the #, to try and
rectify
the signal and just got a high output. I tried a comparator LM339 (i
think)
and i got no response from the output.
The LM339 is far too slow for a 10MHz input among other things its
output stage cannot switch fast enough, faster comparators such as the
MAX999 and ADCMP600 series work well.
I tried everything with and without
an input capacitor (.1uf) and retried most of the experiments with a
10k
pot between 5v and ground to replace the biasing resistors to allow a
finer
adjustment of the input.
I have a feeling my problem is two fold: small signal with the forward
voltage drop of many of the devices i have tried and the speed of the
signal. I'm not sure everything can handle the 10Mhz signal.
On Thu, Mar 24, 2011 at 7:42 AM, Bob Camp<[email protected]> wrote:
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