[time-nuts] No GPS satellites

[Bob Camp]

Hi

All of these older rack mount “GPSDO” products had a fairly long lifespan compared 
to the advances in GPS receivers. When some / most of them first came out, the only practical /proven
way to do timing off GPS was with a downconverter. Without things like serial numbers / date codes it’s 
tough to figure out if this sample of box A has anything at all to do with another sample of the same box. 
On top of that, these are very low volume products compared to normal HP or Fluke
test gear. It’s unlikely that anybody has a database that tells what is what simply from
the serial numbers or date codes. I’d bet that many of them were built to order and rarely in 
groups larger than a few dozen. 

Bob

> On Feb 26, 2015, at 8:19 PM, paul swed <paulswedb at gmail.com> wrote:
> 
> Boy I ran out to mr google and did a search and now I am wondering if some
> versions of the xl-dc just used a plain old GPS antenna. It sure looks like
> that could be the case. The manual does say down converter. Maybe it
> changed over time.
> Regards
> Paul
> WB8TSL
> 
> On Thu, Feb 26, 2015 at 8:15 PM, paul swed <paulswedb at gmail.com> wrote:
> 
>> A fellow time-nut shared the manual for the xl-dc and I downloaded it.
>> It clearly states that it has a down converter. That was very typical of
>> these generation receivers. As examples the Odetics and Austrons. It
>> allowed for very short antenna runs or virtually 0 length antenna runs and
>> losses. The DC468 goes used the same trick.
>> Almost always the receivers show up without the dowconverter because those
>> stay on the roof. Without the down converter the units useless.
>> I have been lucky in some exploits to use odetics down converters with the
>> austron and the another approach using older styles semi-integrated
>> receivers to fake it.
>> So if you want to experiment there is hope. Though it seems each receivers
>> a bit different.The older Truetime manuals were pretty good with schematics
>> and explanations. Unfortunately it looks like the new manual has little to
>> go on.
>> Regards
>> Paul
>> WB8TSL
>> 
>> On Thu, Feb 26, 2015 at 4:46 PM, Bill Hawkins <bill at iaxs.net> wrote:
>> 
>>> Doesn't the DC in the model number mean "down conversion" or something
>>> like that?
>>> 
>>> Seems to me it did in the obsolete 468-DC GOES time receivers, which had
>>> to down convert to about 1.8 MHz.
>>> Also, the down conversion was more than a simple local oscillator and
>>> mixer. You had to have their antenna to make it work, as the mixer was
>>> in the base of the antenna.
>>> 
>>> Bill Hawkins
>>> 
>>> 
>>> -----Original Message-----
>>> From: Tim Shoppa
>>> Sent: Wednesday, February 25, 2015 7:56 PM
>>> To: Discussion of precise time and frequency measurement
>>> Subject: [time-nuts] No GPS satellites
>>> 
>>> Yes, the XL-DC and other Truetime models had as an option for long cable
>>> runs, a downconverter in the antenna. I don't know how to tell the
>>> difference from part number, but I know the truetimes my employer uses
>>> all have the downconverter option and the option is very common.
>>> 
>>> Tim N3QE
>>> 
>>> 
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>> 
>> 
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