[time-nuts] Quieting the HP-113AR Clock/Frequency Divider

[Jeremy Nichols]

Thank you for sharing your experience, Bill. I thought about building a
wooden case and still might. My concern with the metal rack cabinet is that
the metal panels can act as drumheads. In my 113, the 1KHz "singing" is
much reduced once the motor is started. Whether it's drowned out by the
motor noise is a question I've not yet tackled. My 103 frequency standard
has drifted low and can no longer be tweaked back to 1 MHz. Best it will do
is 0.999 998 847 MHz, so the clock will run slow unless I use one of my
other standards. (Having gone to school in St. Paul, I understand the
temperature change challenges.)

Jeremy


On Mon, Mar 19, 2018 at 3:49 AM Bill Hawkins <bill.iaxs at pobox.com> wrote:

> Here's another experience with a 103 crystal standard with the requisite
> 100 KC output and a 113 clock. I craved the clock because I'd seen it in
> the Smithsonian precision time exhibit.
>
> The 103 was certainly quiet, but the 113 was not, in spite of its heavy
> cast aluminum case. The 1 KC stepping motor sings at a frequency that is
> most sensitive to the ear. What were they thinking at HP?
>
> So I built an enclosure in an existing set of shelves. Quarter inch
> paneling defined the enclosure, which was lined with thick fiberglass
> insulation on all sides. The door was an insulated plywood panel that
> had magnetic latches, so you could pull it loose to read the clock. You
> could hardly hear it with the door closed.
>
> Both the 103 and 113 were in the enclosure, reducing the temperature
> changes typical of Minnesota. An external 28 volt power supply trickle
> charged two 12V 7AH batteries with diodes to provide battery power when
> the line went out. At the time, the power company was upgrading
> underground service, so there were many opportunities to observe
> switchover.
>
> I'm sorry to say that I didn't keep detailed records of accuracy. IIRC,
> the clock was within a few seconds of WWV at he New Year.
>
> All in all, another fine learning experience. Sold the 103 and 113 after
> a few years, and got into telephone GPS with a pair of HP Z3801A and a
> 16 foot plastic pipe mast for two HP conical antennas. Ended with the
> Lucent stuff. Inquiries for recycling Lucent stuff welcome.
>
> Bill Hawkins
> bill.iaxs at pobox.com
>
>
> -----Original Message-----
> From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Jeremy
> Nichols
> Sent: Saturday, March 17, 2018 9:39 PM
> To: time-nuts at febo.com
> Subject: [time-nuts] Quieting the HP-113AR Clock/Frequency Divider
>
> Those of us with the 1960-vintage HP-113AR/BR Clock/Frequency Divider
> know how noisy they are. The mechanical clock movement of my 113AR is
> loud enough that I really don't want to be in the same room with it. I
> don't know if the clocks are noisy from brand-new or if the mechanism
> gets noisier as the various parts wear with age.
>
> Here's how I quieted mine:
> . Wrap the outer cabinet of the 113AR in stick-on automotive sound
> deadener.
> . Put the 113AR in a fully enclosed 4U rack cabinet.
> . Stuff insulation into the cabinet so the 113AR is completely
> surrounded except for the front panel.
>
> Should anyone be interested, I can provide detailed notes, a shopping
> list, and pictures. Total cost was about US$150 and would have been a
> lot less if I could have found a used cabinet at the surplus store.
>
> Jeremy
>
>
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