[time-nuts] HP 105B Modification
ed_palmer at sasktel.net
Mon Dec 7 22:53:17 UTC 2009
Yes, I have the same configuration. The part number for the divider
board is 05061-6165. The 10811 + daughter boards are used in the 105B,
5061B Cesium, and the 5065A Rubidium. The circuit loading problem is
exactly the kind of issue I was expecting. Thanks for the warning. I
could probably resolve it by replacing the existing 7474 with a 74HCT74,
but I'd like to minimize the amount of hacking I inflict upon the unit.
John Ackermann N8UR wrote:
> I did something similar to my HP 5065A Rb standard, which had a 10811A
> and a small plug-in card that was a digital IC doing a divide by two
> followed by a simple LC filter. I picked off the signal right at the
> chip input with a small cap and a piece of RG-174 that went to a
> buffer amplifier (I used a two-channel prototype of the TADD-1 with a
> It works fine, except that you need to use pretty loose coupling to
> avoid loading the signal down to the point that there's not enough for
> the divider to trigger on.
> I suspect the 105 (and later 5061As that used 10811s) use the same
> divider card, and the same treatment would work.
> Ed Palmer wrote:
>> I was thinking more along the lines of an analog buffer, but you make
>> a good point. And if I want a sine wave output, I could use a simple
>> pi filter to clean it up. I have an HP 8647A RF generator that does
>> exactly that on the 10 MHz reference output.
>> john.foege at gmail.com wrote:
>>> I have seen a hex schmitt trigger inverter used for this.
>>> The output of the OXCO goes into all 6 schmitt rigger inverter
>>> inputs and then on the output side you have the output leg of each
>>> inverter connected through 300 ohm resistance. Thusly you get 6 hex
>>> schmitt trigger inverters wired in parallel and with a combined
>>> output resistance of 50 ohms.
>>> Very simple and might be just the thing you're looking for.
>>> KB1FSX Sent via BlackBerry by AT&T
>>> -----Original Message-----
>>> From: Ed Palmer <ed_palmer at sasktel.net>
>>> Date: Mon, 07 Dec 2009 11:03:51 To: Time Nuts Mailing
>>> List<time-nuts at febo.com>
>>> Subject: [time-nuts] HP 105B Modification
>>> I have a late-model 105B Oscillator that's equipped with a
>>> 10811-60109 oscillator. It seems a shame to have that nice 10 MHz
>>> source without having access to it. I was thinking of adding a
>>> buffer amp and bringing out the 10 MHz signal. It shouldn't be too
>>> hard, but before I reinvent the wheel, has anyone done this and do
>>> you have any suggestions or advice?
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