[time-nuts] 10811

ka3zyx at comcast.net ka3zyx at comcast.net
Wed May 1 23:15:56 EDT 2013

I just posted some photos at: 

----- Original Message -----
From: "John Miles" <jmiles at pop.net> 
To: "Discussion of precise time and frequency measurement" <time-nuts at febo.com> 
Sent: Tuesday, April 30, 2013 10:53:49 PM 
Subject: Re: [time-nuts] 10811 

> Close, but it's for the 105, not the 5061, and the boards are physically very 
> different. 

The 5061A upgrade used those 105-series boards. With the 5061B, they changed the part number of A1A3 (the OCXO interface board) from 00105-6044 to 05061-6198, but I don't see any major differences in the schematic, looking at the Artek .PDF manual for the 5061B. 

> The part number on the connector for the board is the same as the connector 
> for the 10811. Does anyone know where to get boards that fit the connector? 
> Mouser carries the connector, but I can't find any boards. 

You don't really need a board -- I didn't use one (see http://www.ke5fx.com/tbolt.htm ). It uses a pretty common edge connector that can be pulled off of any number of random surplus HP PCBs, if you don't want to order one. 

> how often do people need to retune the 10811? I have a pair of the 10811- 
> 60109's, another 10811, and a 10544 and all are within 1 Hz of 10 MHz. That's close 
> enough 

Some anecdata: my GPS-disciplined 10811-60109 has been running for about 5 years without any retuning. The DAC voltage is currently about 0.52V, and I'm sure I would have started it out near 0.0, so about 10% of its EFC control range has been needed after 5 years. (Of course it could have wandered around arbitrarily in the meantime, but I doubt it.) 

At -0.324 Hz/volt, this would be about 0.03 Hz per year of positive drift on average, or 3E-9 per year. That's in line with what I've seen other well-settled 10811s achieve. 

> Is there any advantage in using the 723 voltage regulator? The 10811 and 
> 10544 manuals both show the use of the 723 for the regulator for the oscillator supply, 
> but on the HP schematic for the 6198 board they use a pair of three terminal 
> regulators. 

HP's use of an LM317T-style regulator to drive the 18V oven supply, a 78L12 to drive the oscillator, and a Zener+emitter follower to drive the 7474 divider was a bit funky. Regulator noise on the oven supply isn't critical, but for driving the oscillator circuit itself, the difference between a 7812 and an LM317T can be seen in some cases. Not sure offhand how sensitive the 10811 is to supply noise, but you can certainly see the difference in regulators with a Wenzel ULN. 

In any event an LM317T would be fine for driving the +12 rail. 

-- john, KE5FX 
Miles Design LLC 

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