[time-nuts] Squaring Tbolt 10Mhz output

[Greg Broburg]

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<lists at rtty.us>  wrote:
>>
>>
>
>
>
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