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Thread: FM750 + radio RTK signal drop outs - help very much appreciated

  1. #1
    Feldspar
    Guest

    FM750 + radio RTK signal drop outs

    We started using an FM750 with an EZ steer last season with the additional radio module receiving a correction signal from a well known signal provider who covers a good deal of East Anglia.

    Initially there were no problems but after three weeks or so the auto-steer started to cut out. When it did so the satellite strength bars would remain at their maximum (green bars in the top left corner) and the auto-steer could be re-engaged immediately afterwards. One of our operators spoke to another user at a product event who also reported similar problems.

    The pattern of drop outs was difficult to detect. Initially my impression was that the signal drop out occurred at regular spatial intervals suggestive of a radio interference pattern. To test I tried driving back past the exact spot where the drop-out had occurred moments before and no drop-out would occur thus discrediting that theory.

    What did seem to occur was that soon after turning the unit on drop-outs occurred more frequently. After the unit had been on for about half an hour the drop-outs were infrequent but would still occur (about once every 45 minutes).

    Drop-outs occurred in the middle of large open fields so the shading of nearby vegetation was not to blame. There were no power lines / CB radios nearby to cause any possible interference.

    Because we use three of the signal provider's masts over our various farms there was a thought that the device might be switching from the correction signal of one mast to that of another mast and that this might be the reason for the drop-out.


    So my two questions are:
    1. Has anyone else experienced these sorts of problems?
    2. Does anyone have any ideas as to exactly what is going on?

    I will be in contact with the signal provider but I'd like to get my understanding up to scratch beforehand.

    Thanks in advance for your help.

  2. #2
    Field Track
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Are you sure there's a signal loss? Not easy to 'see' but if all the lights are one a few possibles exist:

    Ez-Steer detected the wheel resistance due to a too high, or low setting. I forget which way round it is but you can have it set so it switches off at the smallest touch and thus a bump in the field can make it kick out.

    The Ez-Steer can have a loose sonnection kicking it out but you generally get an error.

    Low power does the same but also gives an error.

    The brushes get dust in them and you can get a lazy motor, or the steering stops working but the machine thinks it is all still OK. A reboot can sometimes help but the best solution is to strip down the motor (quite easy) and give it a good clean out of dust (and leave to dry). Brushed also need taking out and freeing up in their action.

    Signal loss is possible but you usually see you've lost it, etc. If you are 'sure' it is loss and a quick one you might want to check all cables are good and screwed on tight and you can alter the setting from favour accuracy to a lesser one, so possibly covering those losses.

    To get a serious loss you'd have to lose a lot of US Sats really, as autosteer can usually keep going without correction for a little while.

  3. #3
    Feldspar
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Quote Originally Posted by Field Track View Post
    Are you sure there's a signal loss? Not easy to 'see' but if all the lights are one a few possibles exist:

    Ez-Steer detected the wheel resistance due to a too high, or low setting. I forget which way round it is but you can have it set so it switches off at the smallest touch and thus a bump in the field can make it kick out.

    The Ez-Steer can have a loose sonnection kicking it out but you generally get an error.

    Low power does the same but also gives an error.

    The brushes get dust in them and you can get a lazy motor, or the steering stops working but the machine thinks it is all still OK. A reboot can sometimes help but the best solution is to strip down the motor (quite easy) and give it a good clean out of dust (and leave to dry). Brushed also need taking out and freeing up in their action.

    Signal loss is possible but you usually see you've lost it, etc. If you are 'sure' it is loss and a quick one you might want to check all cables are good and screwed on tight and you can alter the setting from favour accuracy to a lesser one, so possibly covering those losses.

    To get a serious loss you'd have to lose a lot of US Sats really, as autosteer can usually keep going without correction for a little while.
    That's a great help, thanks for taking the time to reply.

    I'm not completely sure it's a signal issue. The only thing that convinced me that it might be was the report from someone else who had the same issues, although I did receive the evidence second-hand.

    We were using the system on the press which was pretty rough going but I didn't notice it cutting out only after particularly large jolts. Often it would cut out on pretty easy going. No error messages appear on the screen when it drops out.

    I'll open up the motor and give it a clean. Also when it's put back on the tractor I'll make sure of the connections. The EZ was new last year so hasn't had that much of a chance to get dust in.

    On the point about dropping one correction signal for another you do manually choose which mast you receive the signal from so I would have thought that it would then stay locked on.

    If the RTK signal is lost will the unit automatically switch to EGNOS or will it cut out? I tried both the 'favour accuracy' and 'favour availability' setting with no positive effect. Thinking about it I an obvious thing I didn't try was to turn of the RTK and run it on the basic level of accuracy to see if that helped.

    It might just be a fault with the screen but as you say one would expect an error message.

  4. #4
    Panzer III
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Sorry to go off topic, but I'm at the stage of looking to go to RTK as opposed to EGNOS.

    I'm guessing that your using a Trimble DCM300 modem, and that you had to unlock the 750 and buy in a correction signal from someone. Are you at liberty to break down the costs of the upgrade?

    TIA.

  5. #5
    Field Track
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    I would not rush to take the motor apart, as you get particular issues when the brushes are sticking, or there's dust in there. The motor is lazy and will cut out with an error.

    I think your problem may well be the over ride sensitivity. I can't recall which way round it is but what are you set at and try something else. A front press could well be kicking you out. You do need to find the right balance between making the steering wheel easy to take control and not getting it kick out for reason other than you, etc.

    RTK cost brack down from Egnos as ball park figures is:
    (All approx and my guess - ring a dealer)

    Omnistar unlock 1500
    RTK unlock 1500
    RTK Modem 1000 - 1800 (big guess here)
    RTK Sub around 800 - 1300 per year.

    Might want to consider Russian Sat add-on and here I'm guessing the unlock might 750 but it is only any good really if the correction uses the Russian Sats for correction like only some RTK and some Omnistar options. However saying this the latest 750 firmaware uses the Russian Sats to give you a better 'signal' though Egnos doesn't use them for correction. The result is the latest 750 firmaware doesn't loose Sat counts as quickly as it used to.

  6. #6
    Feldspar
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    I think one of the other guys did fiddle with the sensitivity settings and apparently it made no difference. It was fitted to a newish Massey 6480 and the steering is really quite assisted so that you don't feel when the wheels are going over rough terrain. It might be the motion of the cab as a whole that is disturbing it. I'll check it nevertheless when I next get the chance.

    As a slight aside is it possible to get the 750 screen to beep when it disengages? It was getting jolly annoying as often you would not notice it had cut out until you were metres off line.

  7. #7
    Field Track
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    The front press will have an effect on the over ride setting for sure if it is near the limit. How hard it is against the steering wheel can also have an effect sometimes.

    You really need to narrow down if it is signal, or not. Signal loss generally has a time period of getting back on signal, though RTK is near instant, however losing correction in the middle of the field doesn't mean all bets are off, as you have to lose it for a good while really. Total loss of signal needs the number of Sats to go south, as well as correction which is usually trees, or miltary based dead zones. They do exist but don't move around in the field. Unless the miltary are doing GPS blackout tests in your area but then the whole farm would go not just a point in a field.

    The 750 does bleep and you can alter the volume but it is one bleep and can be hard to hear.

    The 500 you could fit buzzer which was louder and I'm not sure if the 750 can be fitted with it as well now due to recent firmware updates but I could be wrong.

    The remote joystick seems to have a buzzer in it and it brings it closer to you but I'm guessing here in that I think the bleep is closer to me due to the joystick but the joystick is a wiring from hell/purchase issue in that the person selling it needs to know what they are doing - sell you the right setup and it brings little to the party.

    I'd see if you can get the Sonalert fitted to the 750, as this will make the bleep louder.

    As to stripping the motor 99% of the time they'll be errors, or it saying the motor isn't working. It is rare for the unit to think all is well but the motor doesn't move. A reboot solves this most times. The 750 status will also tell you the voltage it is getting and it needs a good supply. You do get probs regardless of power connector.

    The confusing one is a lazy motor, which to be fair can only be detected if you have experiece with the device and you run with a low angles per turn. I like to see the motor gitter, thus when I see it wallying about I can assume 'lazy motor issues' and maybe reboot. Eventually the motor simply cuts out and at this point it needs to be stripped and cleaned and the brushes check and filled to be sure they move freely.

    On front presses I don't use them but all those that do say Ez-Steer needs less weight on the press and more on the front wheels, so you'd maybe lift the front press up a little compared to how you'd run it normally, etc.

  8. #8
    Feldspar
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Quote Originally Posted by Field Track View Post
    The front press will have an effect on the over ride setting for sure if it is near the limit. How hard it is against the steering wheel can also have an effect sometimes.

    You really need to narrow down if it is signal, or not. Signal loss generally has a time period of getting back on signal, though RTK is near instant, however losing correction in the middle of the field doesn't mean all bets are off, as you have to lose it for a good while really. Total loss of signal needs the number of Sats to go south, as well as correction which is usually trees, or miltary based dead zones. They do exist but don't move around in the field. Unless the miltary are doing GPS blackout tests in your area but then the whole farm would go not just a point in a field.

    The 750 does bleep and you can alter the volume but it is one bleep and can be hard to hear.

    The 500 you could fit buzzer which was louder and I'm not sure if the 750 can be fitted with it as well now due to recent firmware updates but I could be wrong.

    The remote joystick seems to have a buzzer in it and it brings it closer to you but I'm guessing here in that I think the bleep is closer to me due to the joystick but the joystick is a wiring from hell/purchase issue in that the person selling it needs to know what they are doing - sell you the right setup and it brings little to the party.

    I'd see if you can get the Sonalert fitted to the 750, as this will make the bleep louder.

    As to stripping the motor 99% of the time they'll be errors, or it saying the motor isn't working. It is rare for the unit to think all is well but the motor doesn't move. A reboot solves this most times. The 750 status will also tell you the voltage it is getting and it needs a good supply. You do get probs regardless of power connector.

    The confusing one is a lazy motor, which to be fair can only be detected if you have experiece with the device and you run with a low angles per turn. I like to see the motor gitter, thus when I see it wallying about I can assume 'lazy motor issues' and maybe reboot. Eventually the motor simply cuts out and at this point it needs to be stripped and cleaned and the brushes check and filled to be sure they move freely.

    On front presses I don't use them but all those that do say Ez-Steer needs less weight on the press and more on the front wheels, so you'd maybe lift the front press up a little compared to how you'd run it normally, etc.
    Thanks once again for your reply. Just to clarify what I said as I wasn't clear enough, the tractor was pulling a trailed press with nothing on the front.

    Panzer has flagged up something that I had completely forgotten about. At one point one of the wires on the T2 unit came loose and was reattached. It might be that it has a poor connection which would explain the EZ steer cutting out but all else seeming fine. I think this may well be it. I'll reconnect the wire and hope that fixes it!

  9. #9
    back'o'beyond
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    To check for RTK drop outs press the info button twice and near the bottom you see "CMR Age" watch this if it goes over 40 sec you will get a drop out, but not before.

    The sonar-alert does work with the 750 and should be fitted as standard in my opinion!

    If you have problems with any GPS system it is always worth going through all the connectors to make sure all good, but from the symptoms you describe it doesn't sound like it is the problem. Also the T2 box is VERY fussy about its power supply so double chech connections right back to the battery.

    I would try adjusting the override sensitivity so you really have to try to get it to disengage ans see I that helps.

  10. #10
    Feldspar
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Quote Originally Posted by back'o'beyond View Post
    To check for RTK drop outs press the info button twice and near the bottom you see "CMR Age" watch this if it goes over 40 sec you will get a drop out, but not before.

    The sonar-alert does work with the 750 and should be fitted as standard in my opinion!

    If you have problems with any GPS system it is always worth going through all the connectors to make sure all good, but from the symptoms you describe it doesn't sound like it is the problem. Also the T2 box is VERY fussy about its power supply so double chech connections right back to the battery.

    I would try adjusting the override sensitivity so you really have to try to get it to disengage ans see I that helps.
    Thanks for the advice - will do as you say.

  11. #11
    WDP
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Are you using the signal from a series of repeaters? Could you be hearing the same signal twice, one being older than the other.

  12. #12
    WDP
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    A base station transmits every other second, repeaters listen for a second and then transmit in the "spare" second, hence their name.

    Hypothetically a base station and repeater 1 are 10 miles apart, repeater 2 is a further 10 miles away, in the same direction. Repeater 2 can only hear the base station through repeater 1, not directly from the base. All 3 are on the same frequency.

    If the tractor is near repeater 1, it may well be able to hear the origin from the base station and the repeated signal from repeater 1, which is 1 second older. This is good. The tractor may also be able to hear both repeater 1 and repeater 2 at the same time, this is also good. The problem arises when the tractor is in the area near repeater 1 and can hear all 3. It can hear repeater 1 on one second, but can also hear both the origin and repeater 2 on the other second, as they will both be transmitting on the same second. Repeater 2's signal is the same as the base, but 2 seconds older, so the tractor ignores them both resulting in intermittent drop out.

    I have set up a network in Northumberland, and this problem took a bit of headscratching to diagnose and then solve, but in the end I can run Agleader along with Trimble, Case and New Holland.

    The answer is you need more than one frequency.

  13. #13
    Feldspar
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Quote Originally Posted by WDP View Post
    A base station transmits every other second, repeaters listen for a second and then transmit in the "spare" second, hence their name.

    Hypothetically a base station and repeater 1 are 10 miles apart, repeater 2 is a further 10 miles away, in the same direction. Repeater 2 can only hear the base station through repeater 1, not directly from the base. All 3 are on the same frequency.

    If the tractor is near repeater 1, it may well be able to hear the origin from the base station and the repeated signal from repeater 1, which is 1 second older. This is good. The tractor may also be able to hear both repeater 1 and repeater 2 at the same time, this is also good. The problem arises when the tractor is in the area near repeater 1 and can hear all 3. It can hear repeater 1 on one second, but can also hear both the origin and repeater 2 on the other second, as they will both be transmitting on the same second. Repeater 2's signal is the same as the base, but 2 seconds older, so the tractor ignores them both resulting in intermittent drop out.

    I have set up a network in Northumberland, and this problem took a bit of headscratching to diagnose and then solve, but in the end I can run Agleader along with Trimble, Case and New Holland.

    The answer is you need more than one frequency.
    Great reply, thanks. The three surrounding masts we use have three different frequencies (don't have the Hz figures to hand) so should that mean this problem does not apply? Depending on which part of the farm the tractor is working I manually select which mast to receive from. I tried switching frequencies within the same field and drop-outs occurred on both settings.

  14. #14
    Ross M
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Hi there Feldspar. I'm guessing you purchased your unit through a CNH dealer as you referred to it as the FM750? What area are you in in east Anglia? please feel free to give me a ring if you still have this problem as i help maintain the RTKF network. 07795 070484

  15. #15
    Feldspar
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Just a quick note to say thanks very much for the advice and to set the record straight. It turns out the problem was the override sensitivity which was set on 60%. Formerly it did take a fair tug to get the motor to disengage and the cut outs did not always occur after large jolts of the tractor so I did not initially think of the override setting and was told that someone had already fiddled with that setting (wrong in the end).

    Nevertheless I have now set it at 0% and have been using the foot switch and have not had a single drop out since. Should have checked that properly first but am pleased to have it fixed.

    Now the only problem is the screen which doesn't seem to work 100% reliably round the edges. Keep pressing the green tick and the unit thinks I've pressed the red cross; I have recalibrated the touch screen with no effect. Is this at all normal due to the type of touch screen used?

  16. #16
    Field Track
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    I think we run the over ride around the 30% - 40%. The lower the number the harder it is to override, etc. Case of find your sweet spot.

    The touch screen and big fingers isn't exact no. We have the same fault.

  17. #17
    Ross M
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    There is the odd CFX-750/FM-750 out there which has the touchscreen problem. Ask your dealer to send it away for repair as the display comes with a 2year warranty.

  18. #18
    Feldspar
    Guest

    Re: FM750 + radio RTK signal drop outs - help very much appreciated

    Thanks Ross.

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