[time-nuts] Odd HP 117A configuration

[Brooke Clarke]

Hi Scott:

If I remember correctly there are two BNC antenna connectors on the A1 box, one 
with DC power for the antenna and another without DC.  Also there's a fuse on 
the DC powered connector which could be pulled.
http://www.prc68.com/I/117A.shtml

An advantage of the loop is that instead of aiming it at WWVB you can rotate it 
to null out the closest RTTY station.

Something I've thought about, but not done is to make time decoder based on a 
PIC micro controller.  Remember the 117 is only a frequency comparator.

There is a free PC program that you can feed the audio output from a receiver 
and it decodes WWVB time code.  The same company has another program that 
decodes the Northern California DX beacons (as controls the receiver 
frequency).  Note the beacons transmit in GPS controlled time slots with 
stepping RF power levels.

Have Fun,

Brooke Clarke
http://www.prc68.com/P/Prod.html  Products I make and sell
http://www.prc68.com/Alpha.shtml  All my web pages listed based on html name
http://www.PRC68.com
http://www.precisionclock.com
http://www.prc68.com/I/WebCam2.shtml 24/7 Sky-Weather-Astronomy Web Cam

Scott McGrath wrote:
> Hi Russ,
> 
> Yes i did and it was a marvelous hack in the best sense of the word,
> It was fascinating to see how this actually worked, it of course is no
> longer necessary and I have removed it in favor of protecting the A1
> assembly fully within the chassis.
> 
> My 117A is a Prefix 438A unit and my manual covers 525A and below.
> I'm still debating whether to use a AMRAD antenna and disconnect the
> +35 from the antenna (by installing a jumper block for reversability)
> or find the proper 10509A loop antenna for authenticity.    I have
> been offered a amp assembly for the antenna by another member so I
> have thought about fabricating the actual loop assembly but I do not
> have dimensions for the loop itself which looks to be center tapped
> which also would  the tube which bisects the loop.
> 
> I bought this a decade ago and was only able to find a manual recently
> always kept it because I knew how rare this unit is.    Right now it's
> been recapped (electrolytics) and I have replaced the chassis mount
> transistors BTW a NTE121 will replace the TO-3 pass transistor if that
> has given up the ghost.    RIght now I am going through the power
> supply board A9 and replacing the resistors many of which have changed
> value after physically rebuilding the PCB which had a 1/2" hole burned
> in the area of R2-4.    One of the challenges of recapping is that
> electrolytics are now much smaller for equivalent ratings so a lot of
> teflon sleeving has been used to prevent potential short circuits.
> 
> So much fun to be had with this stuff!
> 
> - Regards Scott
> 
> On Thu, Sep 11, 2008 at 10:50 AM,  <wa3frp at aol.com> wrote:
>> Scott,
>>
>> Good luck on the rare 117A.
>>
>> Did you get my e-mail with attachment containing the pages of the manual for
>> your updated unit?
>>
>> Russ
>>
>> -----Original Message-----
>> From: Scott McGrath <scmcgrath at gmail.com>
>> To: wa3frp at aol.com
>> Sent: Wed, 10 Sep 2008 12:42 pm
>> Subject: Re: [time-nuts] Odd HP 117A configuration
>>
>>
>>
>> Hi, Ross
>>
>> Please - It would be interesting to see how this worked.   From the
>> date codes on the components my 117A was  built in late 1964 - date
>> codes on conversion module date from 1968. As Tom noted it is a
>> interesting historical footnote from use of the atomic timescale to
>> UTC timescale with leap seconds.     And now due to the influence of
>> embedded device manfacturers who want 'cheap n cheerful' firmware we
>> are now discussing doing away with leap seconds.    Interesting how
>> the pendulum of historical trends oscillates.
>>
>> Right now the 117A is having all the electrolytics replaced while I am
>> reconstructing the PS module trace by trace
>>
>> - Scott
>>
>>
>>
>> On Wed, Sep 10, 2008 at 7:43 AM,  <wa3frp at aol.com> wrote:
>>> Scott,
>>> I had a chance to look at my HP 117A manual last night and saw that
>> your
>>> configuration is described there.  If it is not described in the HP
>> 117A
>>> manual that you have, would you like me to copy those pages and send
>> them to
>>> you as an attachment?
>>> Russ
>>>
>>>
>>> -----Original Message-----
>>> From: Scott McGrath <scmcgrath at gmail.com>
>>> To: time-nuts at febo.com
>>> Sent: Mon, 8 Sep 2008 3:50 pm
>>> Subject: [time-nuts] Odd HP 117A configuration
>>>
>>>
>>>
>>> All,
>>>
>>> I purchased a 117A at a hamfest years ago and am just now looking into
>>> it.     This 117A is a bit different from the ones in the manual and
>>> in pictures up on the web as it incorporates a telechron reduction
>>> motor installed in fthe area in front of the TRF module harness
>>> connector.     Had not looked at this unit much as I did not have a
>>> manual which I now have as the power supply board (A9) had a charred
>>> hole blown in it.     The TRF module does not insert fully into the
>>> chassis due to the presence of the clockwork module.    Interestingly
>>> enough the clockwork looks like HP installed it or someone did a VERY
>>> good job.  Does anyone know what this clockwork is intended for?
>>>
>>> I am now rebuidling the circuit board with glass filled epoxy (West
>>> Brothers + microsphere filler) with a mold/retaining dam made from
>>> silicone rubber.
>>>
>>> Also back when I was at UNH when I was young and foolish a HP 117A was
>>> my introduction to precision timing as Jim Williams in Demerrit Hall's
>>> maintained the frequency standard which consisted of a HP117A and a HP
>>> 5245M frequency counter along with a decade worth of recorder output.
>>>
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>>> and follow the instructions there.
>>>
>>>
>>
> 
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