[time-nuts] TrueTime AL-AK GPS receiver help

Bob Camp kb8tq at n1k.org
Sat May 2 13:57:54 UTC 2015


Hi

Remember - a number of these boxes go *way* back in time GPS wise. Often the basic guts were a mix and match affair and this or that sub-system 
was frozen for a decade or more. At this late date, figuring out why they did that, or why they had multiple sub-systems is going to be tough. I suspect
that it goes something like - this one works with 1500’ of RG-58, that one works with 300’ of RG-58.

In answer to your basic question - I’d bet it has the IF to a GPS receiver and the tuned front end is up at the antenna. I have never seen one of these 
that was an either or as installed. If you wanted a downconverter, that’s what they built into the box. If you wanted a full receiver, that went in instead. 
They flipped a few dip switches on the main board to tell the firmware what it had and moved on.

Bob


> On May 2, 2015, at 12:10 AM, Al Wolfe <alw.k9si at gmail.com> wrote:
> 
>   Does this AL-AK have a real GPS receiver in it? Does the unit have a board with a crystal of 16.368MHz. that is multiplied by 96 up to 1571.328, the mixing frequency to get to the GPS freq of 1575.42?
> 
>   Since the down convert-up convert is offered as an option perhaps TrueTime used an actual GPS receiver in all their units. It stands to reason (at least to me) using a stock off-the-shelf GPS receiver in all their boxes would be simpler than having to do a custom kluge to work at 4 mhz.
> 
>   If this user can find out if his box has an actual GPS receiver then the converter section could probably be bypassed.
> 
>   FWIW, the TrueTime XL-AK used an external up converter and down converter, model 142-6150. Says it's good for up to 1500 feet of RG58. Its manual is on line. It uses the above mixing scheme.
> 
> Al, retired, mostly
> AKA k9si
> 
> 
>> Someone on ebay advised me to contact your website in hopes that someone in your organization can help me with my TrueTime model AL-AK GPS Receiver. I need to send it to someone so that they can check it to see if it works and can track Satellites.  This receiver has the onboard up/down convertor board that changes the receiver input frequency which is set at 4.092 MHz. I don't have the needed down converter at the antenna. I bought this receiver on ebay from someone who told me that he doesn't have the down converter as well and can't figure out how to get it to work at 1575.42 MHz. He also didn't know if this receiver can be setup for a 1575.42 MHz by removing the onboard converter and changing some DIP switches. If one of your members can at least check out the receiver at 4.092 MHz for satellite tracking That would be a big help ...
> <snip> 
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