Possible Furuno replacement for Motorola Oncore?

[WPXS472]

I recently bought a module that was advertised as having the same connector as the Motorola Oncore, but made by Furuno. The module is the same size, with the connector in the same place. The antenna connector is in a different orientation. It has a Furuno GT8031 GPS module, a small micro, and some support components. Has anyone had any experience with this module? I wonder if the micro is converting Motorola data to Furuno format. I think I will try it in my RFTGu GPSDO and see what happens. I have a photo, but unfortunately, it is in a format not supported by the forum.

[cdev]

The Furuno implementation of TRAIM is supposed to be very good.

Otherwise,the older Furuno that I have in my GPSDO is less sensitive than my other GPSs



That said, it may be because of how its configured, and the configurations are not accessible to me in the setting its in, a GPSDO.

The manual is on manualslib.  Also, you can email them. That would  likely be the best way to find out something.

[WPXS472]

The GT8031 is a good receiver, not state of the art by any means. I have some in those little post card size GPSDO boards. They seem to work OK there.
Sensitivity isn't a big concern in a timing receiver. The Oncore isn't all that great. I will try this little board out in my RFTG soon.

[WPXS472]

I installed it in my RFTGu and left it overnight. No lock as of this morning. So, it seems that either the module is defective, or it doesn't speak Motorola.
I do have a socket that fits Oncore Boards. When I get the opportunity, I'll hook it up and see what I get.

[cdev]

If you just needed a timing GPS, and didnt need one that speaks furuno or motorola lingo, there are cheap ublox timing GPSs on ebay right now. Any of them would probably do for you.

[WPXS472]

I specifically wanted a replacement for the old Motorola GPS.

[ZigmundRat]

I’m not familiar with those units, but if it’s faithfully acting as an Oncore clone it will not emit messages automatically. The Oncores (at least the ones I have) power up in silent mode. You have to give it a command to start sending messages (@@Ea01 or something IIRC, which I may not). If it has a battery it will retain that setting  of course but the default is silent mode.

[cdev]

The TruePosition GPSDO card comes wth its own Furuno GPS and you also get a OCXO with AI that entrains itself for its environment. Plus I think there is a connection to the furuno wth its enhanced TRAIM mode.

[WPXS472]

I have a couple of the True Position boards. They are decent boards, but require sending a message to get them going. This is specifically for a Lucent RFTGu-0.

[cdev]

A company  (Synergy?)  is now the distributor of motorola compatible GPS boards. They are expensive, I remember. Too expensive for me. I thought you had a specific application that needed a Furuno compatible GPS timing module.

Despite their lack of sensitivity, my memory is telling me that there was some important reason why some applications do best with furuno, but am having a senior moment now in that I don't remember the exact reason. Ive been told their implementation of TRAIM is very good.

It sure takes a long time for them to find their exact location setting. But once they have found it they are very stable.

[cdev]

I recently discovered that this huge log spiral I got on Tindie makes a pretty good GPS antenna, and pulls in a lot of signal. The smaller 800 MHz log spiral might do better as a general circular polarization UHF antenna but might not pull in as much signal. Anyway, I was wondering how it would do with the furuno. I bet they are complementary. Note that the log spiral is totally passive, so no LNA.

[WPXS472]

In my experience, GPS antennas are kind of weird. I hear a lot about quadfilar helix antennas for GPS, but I have three survey grade antennas and they are patches. In fact, every GPS antenna I have is a patch. I would actually like to try a quad helix sometime. I have seen articles about how to make one, but I don't trust myself to get it right. Over the years, I have seen all kinds of different GPS antennas described in do it yourself articles, but it always comes back to me that the folks who make the ones relied upon by professionals to give accurate results are always patches.

[cdev]

In the hardware documentation for GPSD you may find some other oncore compatible manufacturer.
I dont remeber seeing one specifically but there are quite a few that attempt to mimic another popular manufacturers binary format.

Making a quadrifilar helix GPS antenna is rendered really easy using a nanoVNA2 (using the 2 version is important.

Its basically two loops of stiff wire made so they cross like an egg beater and then twisted approprately. The two loops are rectangularly bent in a square with a gap, and then bent so the gap part is at the top which is where you attach the coax. See the attached files.

See also jc coppens web site,
They are sized so one resonates slightly above the target frequency of 1575.42 MHz and the other slightly below. I have the guts of (an unfinished one) sitting right here. I used approximatey 1 mm copper conduit wire. As long as the two loops resonate at the right frequencies its a no brainer, it basically has to work. The QFH makes a very good antenna because it maintains the right sense of CP (RHCP) properly no matter what angle its used at.


Vaisala's aerosondes contain a nice GPS QFH.. thats the design to emulate, if you can.

I bet it would also be easy to make one using a small cylinder - maybe a pill bottle, and copper tape.

In my experience, GPS antennas are kind of weird. I hear a lot about quadfilar helix antennas for GPS, but I have three survey grade antennas and they are patches. In fact, every GPS antenna I have is a patch. I would actually like to try a quad helix sometime. I have seen articles about how to make one, but I don't trust myself to get it right. Over the years, I have seen all kinds of different GPS antennas described in do it yourself articles, but it always comes back to me that the folks who make the ones relied upon by professionals to give accurate results are always patches.

The GNSS antennas used on GNSS satellites themselves are slightly conical QFH's , for a number of good reasons.

Archimedian and log spiral antennas are also good, especially conical ones which have directional gain. They make good navigation antennas, it seems. better than patch antennas which have some issues. Patch antennas are good for getting accuracy on altitude but they have poor rejection of odd order reflections. which should be cancelled out by the antenna if possible.

[WPXS472]

About that board with a GT8031, it does work. I got one of those Datum Starloc II GPSDOs which use a Motorola Oncore. I unplugged the Oncore, plugged in the board with the Furuno, and a while later, it appeared to have locked. Comparing it to my Thunderbolt verified that it has indeed locked. I am seeing a little slip between it and the TBolt, but without a trusted reference, I don't know which it is. That Datum board looks interesting. The folks over at the Time Nuts didn't care for it because of the way they implement TSIP protocol. Once my cables come in, I plan on using it to test the various Oncore boards I have. The Datum has a vertical on board antenna connector for the GPS module, but most of the Oncores have a right angle connector. I am also going to remote the 10 pin connector so I can experiment with other GPS boards by leaving the Oncore in and substituting the 1PPS from the other boards. I don't know what will happen, but that's why one experiments.

[cdev]

I have the ever-popular Lucent GPS-TMG-26, which is shaped like a small white soft serve ice cream cone. Inside there is a QFH.

In my experience, GPS antennas are kind of weird. I hear a lot about quadfilar helix antennas for GPS, but I have three survey grade antennas and they are patches. In fact, every GPS antenna I have is a patch. I would actually like to try a quad helix sometime. I have seen articles about how to make one, but I don't trust myself to get it right. Over the years, I have seen all kinds of different GPS antennas described in do it yourself articles, but it always comes back to me that the folks who make the ones relied upon by professionals to give accurate results are always patches.

[WPXS472]

Neat! I would like to play around with one. I'll put that in my eBay searches and see if one comes up. There is a European online store, I believe it is "GNSS Store.com" that sells QFH antennas, but they are pretty pricey.

[cdev]

Neat! I would like to play around with one. I'll put that in my eBay searches and see if one comes up. There is a European online store, I believe it is "GNSS Store.com" that sells QFH antennas, but they are pretty pricey.

You can make one.(a qfh)  Its not so difficult. If you have access to a VNA you can even tune it properly.

I paid around $30 for my COTS Lucent. which is also sold under the PCTEL brand. As a timing antenna. Its performance for timing is good. it has an ideal pattern for that.


There is also a GPS-TMG-40 which has a stronger amp in it..

[WPXS472]

Looking around on eBay, there are quite a few for sale with similar part numbers. The most reasonably priced one from the US is listed as  KS24019L112D.
I wonder if it could be a QFH? There are a couple from Asia at reasonable prices, but I am skeptical that they are real Lucent antennas. In looking at the listings, I see quite a few that have the "Don't twist antenna when removing connector" sticker. That is so common that I often see these referred to as "No Twist" antennas. I have one, but I can't remember ever disassembling it to see how it is made. Next order of business. I will report back if it is indeed QFH.

[cdev]

Yes, that is it.

Inside it is  QFH (I will see if I can find a photo of the inside) but it has a fairly sharp SAW filter so this antenna is not good for GLONASS, or any other GNSS, just 1575.42 MHz. GPS

It "kind of works" but not well for GLONASS. (using a fake "M8N" ublox multi GNSS receiver )

If you want an antenna for multi GNSS, a passive one, use a log spiral from Tindie shop of hexandflex - Use a DC block..watch out for ESD at RF input of your GPS.

A log spiral makes a good multi-gnss antenna as its phase center performance  is very very good. Also, they pick up a very strong signal despite not having an LNA (unless you have a good LNA and put it inline).

They make good satellite antennas One side is RHCP, flip it over for LHCP.