[time-nuts] TrueTime AL-AK GPS receiver help
paulswedb at gmail.com
Thu Apr 30 15:54:40 EDT 2015
I can add some insights to way-ward receivers that are missing the down
converters. You can indeed fabricate replacements or like I have done for
several units like Austrons adapted Odetics downcoverters in. This is not
at all easy you have to be time-nutty to do this. It takes reverse
engineering and than almost always a mixer and local oscillator to shift
the signals around. Some of the old rockwell and other gps receivers had
nice IF frequencies at 35 Mhz. Easy to work with. However the more
integrated a receiver is the less likely you can access what you want like
IFs and LOs.
One key thing I ran into is that the receiver you want to make work has to
control the first LO. So that means as an example in the Austrons case
using its 10 MHz LO to multiply up and that same signal had to replace the
rockwell 10 MHz crystal.This required a TTL to PECL conversion and some
really small wires.
You could actually go a more direct route these days and build a LO chain
to 1.5 GHz using PLLs they seem pretty reasonable. Most of the converter
schemes I have reversed engineered seemed to produce a 74 MHz IF or 35 Mhz.
Good luck and if the receiver is going to be scrapped I might want to
Good luck if you move forward.
On Thu, Apr 30, 2015 at 1:55 PM, Alex Pummer <alex at pcscons.com> wrote:
> I am not so sure that it is applying to that case, but there are GPS
> antenna cable extenders which converting down the incoming GPS signal to
> frequencies at which the cable attenuation see here:
> KJ6UHN Alex
> On 4/30/2015 9:50 AM, Tom Van Baak wrote:
>> I received this email. Anyone have a good answer?
>> 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 ...
>> time-nuts mailing list -- time-nuts at febo.com
>> To unsubscribe, go to
>> and follow the instructions there.
> time-nuts mailing list -- time-nuts at febo.com
> To unsubscribe, go to
> and follow the instructions there.
More information about the time-nuts