[time-nuts] XL-DC was Re: time-nuts Digest, Vol 127, Issue 33

[Doug Ronald]

In my XL-DC's case, there must have been a downconverter built into the antenna (which I don't have), but there was an upconverter in the chassis which took the IF signal from the cable, and heterodyned it back up to L-Band. I haven't fiddled-around with the upconverter, but I suspect the IF was in the HF band.

Overnight my XL-DC says the GPS is unlocked, but is tracking 6 satellites, so my troubles still persist...

-Doug

-----Original Message-----
From: time-nuts [mailto:time-nuts-bounces at febo.com] On Behalf Of Russell Rezaian
Sent: Friday, February 27, 2015 10:12 AM
To: Discussion of precise time and frequency measurement
Subject: Re: [time-nuts] XL-DC was Re: time-nuts Digest, Vol 127, Issue 33

I can confirm there are at least two common varieties of the XL-DC GPS RX board.

One uses a "normal" GPS antenna (no down-converter, provides DC on the antenna line for an amp in the antenna, the typical antenna provided seems to be an AeroAntenna AT575 variety, but I suspect other antennas that are similar should be fine).  The specific antenna part I have is:  
AT575-142TTW-TNCF-000-RG-41-NM

It's been a while since I last decoded that part number but it's a very easily re-useable general use GPS antenna with an integrated RF amp.  
Works over a fairly wide range of DC supply voltages and claims a slightly higher gain than some other standard timing GPS ice cream cones.

There are also versions of the GPS module for the XL-DC that use a GPS antenna with an integrated down converter that is actually physically part of the antenna provided.

The down converter antenna is normally a single integrated unit. The part numbers I see on one I have handy are 140-614 (TrueTime) or Model
142-6150 on the Symmetricom label.

I don't have any details for the voltages or whether there is a reference frequency provided for the down converter style receiver.

I have seen some suggestions that they also had a dedicated down converter module that could be used with "normal" GPS antennas, but I don't have any details on that option.

If you have a RX module that needs the converter antenna there should be a clearly visible little label indicating this on the module itself near the antenna connector.  If you don't have that label the RX should work with most GPS antenna systems (and also with most antenna splitter systems too).
--
Russell

Al Wolfe wrote:
>    I have an XL-DC and it has an internal GPS receiver in it. It 
> supplies and monitors 5 volts to a BNC antenna  jack for an external 
> amplified GPS antenna. I don't know what the internal GPS engine is 
> but doubt if it is anything special.
>
>    The manual describes the down converter system as an option.
>
> Al, k9si
>
>
>> 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
>>
>
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