[time-nuts] WTB: GPSDO

Chris Albertson albertson.chris at gmail.com
Fri Mar 10 17:35:05 EST 2017

A GPSDO is not hard to make.  All you need is some way to compare the
phase of two signals, an XOR gate can do that.  Then a small $2
process moves the control voltage on the crystal.    I tried one to
build the simplest GPSDO that could still work.   Got the parts count
down to about four or five and the cost well under $10 plus the OXO
which was about $20.  The simplest dumb one I could make keeps about
e-10.  Not great but enough for many uses.   I compared to my
Thunderbolt and I could see the phase advance and retreat.  Just a
little most sophistication and I likely could do much better but my
goal was to prove to myself that a GPSDO could be build VERY simply
with cheap parts

On Fri, Mar 10, 2017 at 1:39 PM, al wolfe <alw.k9si at gmail.com> wrote:
> Jeff,
>     I have been using a TrueTime XL-AK purchased on eBay a few years
> ago. It has worked flawlessly for the last five years. It seems to
> work well with most amplified antennas that I have tried. Supposedly
> accurate to better than 10 -12 but I have nothing to compare it to. It
> will supposedly control an external oscillator. Mine has five 10 mhz.
> sine wave outputs as well as IRIG-B out.
>     I paid around $150 for mine, but it seems they are asking around
> $500 these days. With patients they can be had for less.
> Al, k9si
>> On 3/9/2017 3:45 AM, Jeff AC0C wrote:
>>> We had a small tornado come through north of our house about 1/2 mile on
>>> Monday.  Really did a number on the antennas.  Only electronics impacted
>>> was my old Nortel GPSDO.  It’s pretty much deaf now, as far as I can tell.
>>>  The Nortel always had a hard enough time obtaining the initial lock in
>>> the past on startup, but since “the event” it’s been no joy.
>>> So I’m in the market for a GPSDO.  Key application here is as a bench
>>> precision frequency reference.  Something with good composite noise
>>> performance close in.
>>> If you have a suitable GPSDO in solid operational condition, kindly
>>> contact me off list.  Thanks!
>>> 73/jeff/ac0c
>>> www.ac0c.com
>>> alpha-charlie-zero-charlie
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Chris Albertson
Redondo Beach, California

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