[time-nuts] Looking to find an antenna for a TrueTime XL-DC

[Rick Jones]

I have been bequeathed a TrueTime XL-DC, Model 151-601-1, serial number
1671 per a sticker on the side. On the back, on the right as one faces
the back, is a small sticker that says "Down Conv. Req'd"

Unsurprisingly, it has arrived without an antenna. If the original
antenna still exists, it is on a building roof in Ft. Collins Colorado
and is likely effectively lost. (I'm in Sunnyvale, CA)

HalM was kind enough to come over the other day with some antennae which
we tried without success. Since then I've done a bit of web searching
and come across:

http://www.prostudioconnection.com/Symmetricom-TrueTime-GPS-Antenna-140-615-Downconve-p/282092173717.htm

It seems to be a part that was (also) included in a larger down/up
conversion product, the 140-6150. I was wondering if the naive
assumption that "TrueTime down conversion is TrueTime down conversion"
and the sticker on the back of the DC-XL might mean the 140-615 antenna
would work with the DC-XL?

thanks muchly,

rick jones
intrigued member of the peanut gallery
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[Hal Murray]

HalM was kind enough to come over the other day with some antennae which we
tried without success.

I was going to suggest taking the cover off and looking inside but it fell
off my to-do list.

GPS receivers are reasonably specialized. I doubt it anybody makes one
targeted at the down-converter market.

Is there an up-converter in there feeding a normal receiver? If so, it might
be possible/easy to bypass.

If it looks like a direct connection to a normal receiver, I'd guess it has
special firmware. It might be possible to replace it with one with normal
firmware.

[Rick Jones]

Post by Hal Murray

HalM was kind enough to come over the other day with some antennae which we
tried without success.

I was going to suggest taking the cover off and looking inside but it fell
off my to-do list.
GPS receivers are reasonably specialized. I doubt it anybody makes one
targeted at the down-converter market.
Is there an up-converter in there feeding a normal receiver? If so, it might
be possible/easy to bypass.
If it looks like a direct connection to a normal receiver, I'd guess it has
special firmware. It might be possible to replace it with one with normal
firmware.

My peanut gallery level of knowledge means I wouldn't recognize a normal
receiver if it reared up and, well, you know :)

I do though have some pictures of the relevant section of the machine
with the cover off - two of the same shot at:

ftp://ftp.netperf.org/dc-xl

The antenna connection is the silver "square" on the left. There are,
as you can see, a number of jumpers everywhere. The daughter card is
connected at its "top left" in the picture where those "5s" of posts
are. There are some shiny gold (plated?) posts there underneath them,
and a couple other vertical connections more towards the center.

That entire assembly can slide out of the chassis after removing four
screws at the back. I didn't try to remove the daughter card.

rick jones

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[Alexander Pummer]

Meinberg https://www.meinbergglobal.com/ makes complete down and up
converter for GPS remote antennas

73
KJ6UHN
Alex

Post by Rick Jones

Post by Hal Murray

HalM was kind enough to come over the other day with some antennae which we
tried without success.

I was going to suggest taking the cover off and looking inside but it fell
off my to-do list.
GPS receivers are reasonably specialized. I doubt it anybody makes one
targeted at the down-converter market.
Is there an up-converter in there feeding a normal receiver? If so, it might
be possible/easy to bypass.
If it looks like a direct connection to a normal receiver, I'd guess it has
special firmware. It might be possible to replace it with one with normal
firmware.

My peanut gallery level of knowledge means I wouldn't recognize a
normal receiver if it reared up and, well, you know :)
I do though have some pictures of the relevant section of the machine
ftp://ftp.netperf.org/dc-xl
The antenna connection is the silver "square" on the left. There are,
as you can see, a number of jumpers everywhere. The daughter card is
connected at its "top left" in the picture where those "5s" of posts
are. There are some shiny gold (plated?) posts there underneath them,
and a couple other vertical connections more towards the center.
That entire assembly can slide out of the chassis after removing four
screws at the back. I didn't try to remove the daughter card.
rick jones
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[Martin Burnicki]

Post by Alexander Pummer
Meinberg https://www.meinbergglobal.com/ makes complete down and up
converter for GPS remote antennas

That's true, but they have been designed for the frontend assembled in
Meinberg GPS receivers. I doubt they work with Truetime devices.

Martin (working @Meinberg)

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[paul swed]

Completely agree with the comment on working with other receivers.
The down converters had to match the IF and there were at that time at
least 2 IF frequencies 75 and 34 MHz as I recall.
But that said no idea what they may cost and is it worth the gamble.
Or reach out to meinberg and ask.
Regards
Paul
WB8TSL

On Sat, Aug 6, 2016 at 4:19 AM, Martin Burnicki <

Post by Martin Burnicki

Post by Alexander Pummer
Meinberg https://www.meinbergglobal.com/ makes complete down and up
converter for GPS remote antennas

That's true, but they have been designed for the frontend assembled in
Meinberg GPS receivers. I doubt they work with Truetime devices.
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[Bob Camp]

Hi

Add in variables like supply voltage, tuning approach, signal levels, and gain ….

There are a lot of things you need to match up to get a downconverter going
with an old style GPS. Once you do, you then likely have a unit that has GPS
epoch roll over issues. It may have other firmware quirks as well.

None of that says “don’t do it”. It simply is a caution that this is a labor of love rather
than one getting a useful piece of gear up and going. You may ultimately have something
useful, the odds are it will have bugs …

Bob

Post by paul swed
Completely agree with the comment on working with other receivers.
The down converters had to match the IF and there were at that time at
least 2 IF frequencies 75 and 34 MHz as I recall.
But that said no idea what they may cost and is it worth the gamble.
Or reach out to meinberg and ask.
Regards
Paul
WB8TSL
On Sat, Aug 6, 2016 at 4:19 AM, Martin Burnicki <

Post by Martin Burnicki

Post by Alexander Pummer
Meinberg https://www.meinbergglobal.com/ makes complete down and up
converter for GPS remote antennas

That's true, but they have been designed for the frontend assembled in
Meinberg GPS receivers. I doubt they work with Truetime devices.
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[Rick Jones]

Post by Rick Jones
I have been bequeathed a TrueTime XL-DC, Model 151-601-1, serial number
1671 per a sticker on the side. On the back, on the right as one faces
the back, is a small sticker that says "Down Conv. Req'd"
Unsurprisingly, it has arrived without an antenna. If the original
antenna still exists, it is on a building roof in Ft. Collins Colorado
and is likely effectively lost. (I'm in Sunnyvale, CA)
HalM was kind enough to come over the other day with some antennae which
we tried without success. Since then I've done a bit of web searching
http://www.prostudioconnection.com/Symmetricom-TrueTime-GPS-Antenna-140-615-Downconve-p/282092173717.htm
It seems to be a part that was (also) included in a larger down/up
conversion product, the 140-6150. I was wondering if the naive
assumption that "TrueTime down conversion is TrueTime down conversion"
and the sticker on the back of the DC-XL might mean the 140-615 antenna
would work with the DC-XL?

In parallel I contacted the support folks at Microsemi via their
website. They were kind enough to reply to let me know that the 142-615
will not work with the downconverted XL-DC model above. They suggested
that perhaps a 142-603 or 142-610 would work so I'll cast about the web
some more.

happy benchmarking,

rick jones

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[Hal Murray]

It IS possible to hack a ’standard’ SV6 receiver such that it will work in
the XL-DC...

Did your XL-DC have an actual SV6 in it? I didn't see one in the picture
Rick sent out a few days ago. There was a Trible sticker on a chip so I
suppose the logic from a SV6 could have been laid out as part of another
board.

[Tim Shoppa]

My first ever GPS receiver was a surplus SV6. Wow, that's a primitive
receiver. The PPS would shift by 6 milliseconds (not microseconds, but
milliseconds) every time I didn't have enough satellites in view.

Tim N3QE

Post by Hal Murray

It IS possible to hack a ’standard’ SV6 receiver such that it will work

in

the XL-DC...

Did your XL-DC have an actual SV6 in it? I didn't see one in the picture
Rick sent out a few days ago. There was a Trible sticker on a chip so I
suppose the logic from a SV6 could have been laid out as part of another
board.
--
These are my opinions. I hate spam.
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[Gregory Beat]

Here is the Manual for the True Time XL-DC (circa 1997-1999)
http://glacier.lbl.gov/gtp/DOM/Support/xl-dc-manual.pdf

gb

Sent from iPad Air
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