I’ve picked up a couple of sca12s boxes recently and am putting them through some tests. (Full disclosure: actually one is a Sokkia gsr1200 and the other is a gir1000, both are Ashtech sca12s clones.)

I know some on this board have been around these things since the beginning, so I would appreciate your input on some of their idiosyncrasies.

First of all I found them to be very touchy about their I/0 connectors and power supplies. I got an I/O cable with one receiver. The cable is setup for a data collector on com- A, DGPS on com-B via DB9 and a PC DB9 on com-C

At first I was only able to power up one receiver intermittently and the other one hardly at all. I tried some contact cleaner and tested the power and ground pins. The power seemed to be coming through fine, but still very intermittent powering up the one receiver and the other I finally got started once.

There didn’t seem to be any rhyme or reason to it, except that it helped letting everything rest for a while. Anyway I cobbled together a custom I/O cable using an old DB25 printer cable. After a couple of tries I’ve finally got a cable that works reliably to power on the receivers, and I finally figured out that the pin out for the DB9’s has to have the wires for the “clear to send” and “clear to receive messages” included. ( The original Sokkia cable still is very intermittent).

I’m using 12 volt AC to D/C transformers for all this and I found that the GPS units also would not work using a 1.4 amp power supply. I could only get the LED light to flash orange for less than a second using that bigger brick. A 500 MA 12 volt converter seems to be working O.K

SO MY FIRST QUESTION- Do these things tend to have problems with their I/O connectors as they get old, and should I expect any problems using a 12 volt power supply on a big boat?

To make a long story shorter I’ve finally got both GPS units working using Ashtech Evaluate software. I’m starting to learn how the command system works and have created a .gps initialization file. The receivers seem balky at accepting commands, but I’ve finally got them putting out enough NMEA data to work with other software packages. The gsr1200 has carrier phase with the most up to date firmware 1J and the gir1000 does not have carrier phase and is using firmware 1L.

BIG PLUG HERE- One thing I really like about Ashtech is that their equipment is almost always thoroughly documented- AND the old information and software is still on the FTP site. I would not be this far along without that kind of help....along with the information on this forum.

Anyway the primary reason I’m interested in these things is to have a more accurate GPS unit for outputting NMEA data on a dredge. I’ve got an existing device to receive, record and display the data. I would like to hook up a 4800 baud garmin DGPS beacon to these GPS units but the garmin would like to receive a tuning message at start up.

My testing is showing that the horizontal accuracy of the SCA12’s even without a beacon is pretty good at about 4 meters at 95% assurance and less than 2 meters at 50%. What is really nice is how rock solid their position is. Drift is in the order of only about 0.8 meters per minute.

My main concern now is that even though I am sending them the “save settings to battery backup command”, it seems like they have to be initialized using Evaluate each time they are powered down and restarted.

SO I guess my next question is this..... Is it possible that some of the problems that I’ve been observing are related to a worn out internal battery? Can that be fixed? Might it charge up if I run them regularly? I’m beginning to wonder if these old workhorses are robust enough to work reliably as NMEA transmitters without constantly having to fiddle with them.

Any advice related to the SCA12’s , using them with DGPS and programming would be much appreciated.
Modified By L.A. Johnson on 1/28/2007 at 6:09 PM

never used them. but in general i'd be a little worried about using these to control the "boat" until you get the bugs out. my guess it that it may be the power connector on the inside. a very common problem for all electronics is where external plugs are attached to the boards. i've fixed a number of radios by simply applying fresh solider to these connections.

That multi cable can indeed be the problem. Last I checked they were $240 if you could find one.

Go to the Magellan ftp site and get the wiring plan. Take your old cable, your experiment and the diagram to a professional cable guy. You want someone who can do the waterproof connections. The com connectors are easy.

Power connectors require research.
What I have are from Force Electronics which I purchased through Heilind in PA.

Customer Part # TA3F
Manufacturer Part # SWCTA3F

and

Customer Part # TA3M
Manufacturer Part # SWCTA3M

They were cheap enough that I decided to match the original. If you don't care, cut your wires and use trailer connectors from an auto parts store.

Paul in PA

for the cable, you might even call Hayes Instrument and see if they might just have one in a box of stuff looking for a new owner

Lee, Thanks for the suggestion. The ribbon cable inside is like a thin circuit board with solder connections for the pinned connectors on each end. I’m not ready to take a solder gun to it yet. If I can get it working reliably it will not be driving the boat- only helping the operators guide it… and letting me know where it's been.

LPL, I already cut the power connector off the original cable because it seemed a little erratic. I’ve got good solid power to the correct pins and what seems like a good ground, but that old cable just won't power up either unit except every so often.

It’s funny… I’ve got a homemade cable that will power up either receiver every time, but when I started on building another one using another old PC cable it seems to produce the same intermittent power problem. If I get this thing working right I will want to build a custom cable anyway.


JD… I’m not really a big Hayes customer, but I might just give them a try. I would like to have a good short connector -Ashtech model A730124.

For all… I now have a little over 7 hours of NMEA data logged using SA watch software. The actual statistics for 99% horizonal accuracy are 4.7 meters, 95% is 4.1 meters, 68% 2.2 meters and the 50% assurance is down to 1.6 meters. Drift is still less than 1 meter per minute. The error bias is to the North and slightly Northwest which is typical for this part of the world. This is with no DGPS input yet

I’m encouraged because it seems the NMEA settings stuck after a brief shutdown… even though I went back to logging with the SA watch software.

The one unit replies back that it is a model sca, firmware 1j00 and is PBE-m-onur unit. The P stands for carrier phase, B is for differential base station but the E is not listed in the manual. How can you tell if it is a decameter or CM unit ?


And how do I get the carrier phase data out of it? … What are the raw data –settings? I assume it logs to internal memory which is 2MB. I’m going to take a look at Ashtech download and the RCC software. And what is that HOSE software and what about the trial version of geodetic base station ?

HOSE is the download routine. If you've got Solutions it should download the data as well.

JD is correct about contacting Hayes for those obsolete cables. I can personally tell you that about 3 years or so ago they had a 4'X4'X4' cardboard box full of vintage cables and such....including several of the SCA cables (cause they let me dig through the stuff). I'd suggest calling them and talking to Randy Black.

Dangerous Dave

Lots of questions..lets see...

Ports B and C have hot power pins...don't let those pins touch other metal objects in your backpack or the case as it can short out the cable....been there, done that..

I usually don't have good luck with direct 12v power supplies working on these..I have seen the orange light and/or no antenna power with plug in supplies versus using a battery. (You could certainly run the 12v charger on the battery at the same time, it just seems like the battery buffers the variations in power from an AC adapter).

If your units lose their settings after ALL power is removed from the cables, then the internal backup battery is dead.

You can run a couple of simple tests. First, run either Commander or Remote and type (with caps lock on) $PASHS,CLM

Your response should be ....wait...... and then passed and it should respond with 2288 kwords...If you don't get 2288 then the internal memory could be fouled up..

Then change your recording interval to 1 second ($PASHS,RCI,1) and then save it ($PASHS,SAV,Y).

remove all power from the unit (disconnect both the power supply AND take the serial port off your computer, remember the hot pins)...

Now check your settings again using $PASHQ,PAR AND $PASHQ,RAW...if it goes back to 20 second recording interval then internal batt is gone...

send it to Pete at The Stereo Doctor in Augusta, Maine....he does mine constantly..

Those units that have the P option are storing carrier phase to internal memory already. Decimeter vs CM units are in the RELIANCE PROCESSOR software, not the unit itself....IF it has P option ,then it'll do sub cm work..

>It stores b and e files in memory with or without a controller, and stores the d-file from the controller if you have hooked one up...D files are time tagged attribute files, and are NOT the same style as created by PM2's and other newer units that download into Locus or AS or GNSS.
Modified By Robert Bills on 1/29/2007 at 10:56 AM

I can dowload my SCA 12 in Solutions. Just plug it in and Solutions finds it.

Paul in PA

Thanks everyone for taking the time to respond… and Robert thanks a million- those are some very useful tips.

I know you guys love your sca12s and reliance systems- at least you used to. I’ve read just about everything on this board that a search for sca12 turns up. Working with these things can be kind of fun- like knowing the secret handshake- PASHQ,PAR anyone?

Robert, It looks my cables are set up somewhat different than on the Ashtech A730124 drawing. I don’t think there are any hot pins. It looks like pin 4 on the Ashtech B & C com DB9s are hot- presumably they are females and intended to power a beacon or something.

On my Sokkia cable the Com 3 connector is setup the opposite of the Ashtech so that a null modem connector is not required to connect to a PC serial port- and no hot pin. My com 2 connector looks like it only has pins 2, 3 & 5 used, which is typical for hooking up a DGPS beacon.

I was able to get the one receiver that is more responsive to the old cable started by plugging it into a 12 volt dry cell battery. Then I unplugged it and it wouldn’t start again. Tried again a few minutes later an it started- Something is wore out, erratic…... mostly I suspect the cable

So now I’ve got it plugged in and was able to get the garmin RTCM correction beacon attached and working on com 2 at 4800 baud. Farily impressive results so far too… I’ve only been logging for about an hour now but 99% confidence accuracy is 1.5 meters, 95% 1.4 meters, 68% 1.1 meters and 50% 0.9 meters. Interestingly the drift has picked up noticeably to 3 meters per minute, but the moving around is in the 1 meter circle so I guess that’s not too bad of a trade off.

So things are going pretty well- still need to do some testing of the internal lithium battery….

But I’m also wondering about a few things…. maybe it’s better to just try to figure them out myself, but it’s certainly not clear to me at this time.

I see that you can turn on a number of raw binary data messages and send them out to a com port. The MBN and PBN messages should be useful to calculate position and there are references to sending out carrier phase related information, if available, in the MBN binary message. What PC software is typically used to log these binary messages and what software is used to convert/process or read them?

Also if carrier phase raw data is logged to internal memory automatically- what happens when the internal memory fills up? So far the regular Ashtech download software does not want to connect for me, but I’ll keep working with it to download some data soon I hope.

One last question even though I’m afraid I know the answer. It looks like the SC12s always starts up at 9600 default baud on all the com ports. If you want something different do you have to manually change the baud rate after each start up… or can something different be programmed in? If I had my way I would like to have the unit startup at 19,200 baud on port A, 4800 on B and then com C could be at the 9600 baud default for occasional PC monitoring.

I suppose I could just install it un-switched and let it run 24-7…. That might be the best approach anyway.

download datalogr.exe (dos program) from the ftp site. Connect to port a or c and run. It asks for a site id (4 letter site name) and then IT sends the appropriate $pashs commands to log binary directly to b and e files.

You use a pash command to set the baud rates on the various ports. I can't remember it off the top of my head without more coffee ( or less coffee)..Anyway, you use the numbers 1 through 5 to set the baud rate and don't forget to save the settings with pashs sav command. This command is used on each port separately.

Remember these receivers were built when com ports used slow uarts and buffering was a new fad. I don't know if they get faster than 19,200..Read that fine manual.......

If your unit doesn't remember settings the internal batt is gone....NOTE...this also can affect the on/off switch. You may see that you can't turn it on using the switch but as soon as you attach it to a pc and start talking the unit begins working.

Datalogr seemed to make all the correct settings by itself and worked right out of the DOS box. The files processed against my rinex base station data in Solutions- Very cool.

I now feel that most of the receiver startup problems and certainly loss of saved settings are related to weak internal batteries. One unit seems to be starting to recover; the other would like to have a heart transplant from the stereo doctor. I talked to Paul in PA. and he brought me up to speed on a few things. Thanks again for your help.

Following are NMEA logging statistics for a SCA12S using an inside the building coast guard beacon accepting RTCM corrections from a transmitter about 25 miles away- (typical 4 second latency). The site has a good but not perfect external antenna location and not a fancy antenna, but it meets the receiver specs for voltage and gain after adjusting for cable loss. This antenna location has been monitored with post processed L1 and adjusted to HARN control a number of times.
Default SCA12 satellite mask of 5 degrees and all the other default settings that I don’t know about yet….

12 hour overnight test:
99% horizontal accuracy within 2.7 meters
95% - 1.8 meters
68% - 1.1 meters
50% - 0.9 meters
Drift - 3 meters per minute
Error in the mean of all points compared to the known- 0.3 meters- bias to the North and slightly west

13 hour daytime test:
99% horizontal accuracy 2.8 meters
95% - 2.2 meters
68% - 1.1 meters
50% - 0.9 meters
Drift - 3 meters per minute
6 to 11 satellites were available over this period. HDOP always less than 2


8 hour overnight test with receiver #2:
99% horizontal accuracy 2.9 meters
95% - 2.0 meters
68% - 1.1 meters

50% - 0.8 meters
Drift - 3 meters per minute


Modified By L.A. Johnson on 1/31/2007 at 9:56 AM

You can still buy new the Medusa cable as it is used for almost all sensor boxes.