[carlh]

Hi guys

Our 10yo Autofarm RTK system which works off our two base stations is beginning to show it's age and I'm starting to have an issue our dealer believes is with our roof array, or most likely the two white dome antennas attached to the dish on each side. What is happening is that when I turn around, it shifts me across 1-2inches, but will then correct itself when I turn around and head in the original direction, but will keep shifting everytime the tractor does a 180 degree turn.

We switched the left and right dish around last year and re-calibrated the screen, however we're back at square-one now.

Our dealer in Australia is quoting $1000 each (or $3000 each new) for second-hand antennas which are likely as old as ours, so I'm investigating potentially fitting a L1/L2 antenna from Aliexpress (I'll put some links below for some that I think might be okay, although will need some modifications to our dishes to attach them).

I've been trying to research our particular antenna (AeroAntenna AT2775-83W-TNCF-000-RG-39-NM), but the closest I've come is the AT2775-81, which I can only assume is the same capacity/components but a different enclosure. See details below:

AT2775-81.pdf

I tested 11.55V coming out of the antenna wire, so any replacement will need to be able to manage this voltage.

My question is, will other much cheaper antennas do the same job provided it can handle the voltage, L1/L2 GPS, the gain is the same etc? Or is this even the issue, or is there something else I could try? Any help appreciated.

Here is one I have found on Aliexpress:
BEITIAN high quality GLONASS BDS GALILEO GPS antenna

 

[m_elias]

GPS tech has come a long way recently so cheaper shouldn't necessarily mean inferior. I've used $50(USD) antennae from arduSimple for my F9P based RTK guidance system which tracks L1/L2/L? for GPS, Glonass, Beidou & Galileo satellites.

We still use several Autofarm 5001 systems with the 3 antenna roof array. What you describe makes me wonder if your side to side antenna offset setting is correct. What happens when you drive the same pass in both directions? Is there a constant offset?

When we've had to replace the antennae on the roof it's usually shown up as tracking less satellites then the other antennae on the GPS details/status page.

 

[carlh]

Thanks for the quick reply - yep if I drive let's say North on two runs it'll be the same offset and likewise if I'm heading South on two runs, they'll both be offset say 2 inches. Hope that's clear?

Is there somewhere I can check the offset setting? Cheers

 

[joesixpack]

Are you sure your left/right offset is correct?

 

[m_elias]

Are you sure your left/right offset is correct?

This is what I was suggesting although once setup it shouldn't need to be adjusted. On our older systems we access it via a system menu with a passcode.

Another thought, does your system have an attitude survey option? It's a 30 min procedure where the Autofarm calibrates it's position readings while you're parked on flat level ground. It's most useful when swapping receivers or roof arrays between tractors but we do it at the beginning of each season. Without it, the Autofarm can do some strange things.

 

[joesixpack]

Ah yes that as well! If the gyro’s think they are on an angle and they are not it is going to mess with your line.

 

[carlh]

Ah yes that as well! If the gyro’s think they are on an angle and they are not it is going to mess with your line.

The dealer did a calibration at sowing time last year but to be honest can't remember exactly what we did. I have the password to access the service menu though.

My screen does have an attitude survey option though, is that where I should start or is there somewhere I can view if my left/right offset is correct (I'm not sure what you mean by that sorry)?

 

[joesixpack]

The dealer did a calibration at sowing time last year but to be honest can't remember exactly what we did. I have the password to access the service menu though.

My screen does have an attitude survey option though, is that where I should start or is there somewhere I can view if my left/right offset is correct (I'm not sure what you mean by that sorry)?

Well I don't have any Autofarm experience just a lot of Trimble so I'm extrapolating a bit here but in general as long as the navigation controller has terrain compensation it measures the slope of the tractor and corrects for it. If you haven't adjusted this slope you will be off the line because the tractor thinks its tilted.

Once that is correct then there still is a chance its slightly off line say from the antenna not being perfect in centreline or say still a small offset produced from terrain corrections. Thats what you zero out with the left/right offset.

There's still a change there is something wrong with the antenna's, but could even be with the terrain compensation. Which you might be able to turn off to diagnose the antenna.

Either way if I had to spend much on it I'd sure be tempted to upgrade rather that throw money at something that aged.

 

[carlh]

Thanks for the help. I'll have a play around in the settings tomorrow and see what I can come up with.

 

[wvca]

it's too bad you didn't ask earlier ...
my autofarm antenna went for $2 at an auction yesterday here ../.twin antenna
nobody had one or no interest in it, went to high bidder, was setup for rtk but no rtk modem / radio

 

[carlh]

I was wrong, I don't have an Attitude Survey button... I've added a couple of pics from this morning. Both antennas are reading 10+ satellites and the POS is a nice low number, but still having issues with it skipping over 2 inches. I guess with both antennas seemingly being okay we can rule them out (I guess?) so possibly there is a calibration I should be trying?

I did the normal 'survey position' on startup and had a look through the calibration options but didn't want to fiddle around with anything I couldn't change back and nothing really stood out as something that might fix it. Any ideas of what I should be trying?

 

[m_elias]

Did you figure this out? When you're in the Service Menu, go into the Examine Attitude page. There you might have the Survey Attitude option.

If you drive north along a pass, then turn around and drive back south along the same pass, stop mid way and look at how far beside you are on the south pass. Half of your error is the amount that you need to adjust in the Adjust LeverArm menu.

 

[carlh]

Did you figure this out? When you're in the Service Menu, go into the Examine Attitude page. There you might have the Survey Attitude option.

If you drive north along a pass, then turn around and drive back south along the same pass, stop mid way and look at how far beside you are on the south pass. Half of your error is the amount that you need to adjust in the Adjust LeverArm menu.

Thanks for getting back to me. Yes got it sorted with the help of a local tech who used to deal with Autofarm gear (not the dealer). We did the 24hr survey and that sorted it out! Thinking it might be worth doing that each year. Cheers

 

[carlh]

Did you figure this out? When you're in the Service Menu, go into the Examine Attitude page. There you might have the Survey Attitude option.

If you drive north along a pass, then turn around and drive back south along the same pass, stop mid way and look at how far beside you are on the south pass. Half of your error is the amount that you need to adjust in the Adjust LeverArm menu.

Thanks for getting back to me. Yes got it sorted with the help of a local tech who used to deal with Autofarm gear (not the dealer). We did the 24hr survey and that sorted it out! Thinking it might be worth doing that each year. Cheers

 

[m_elias]

Thanks for getting back to me. Yes got it sorted with the help of a local tech who used to deal with Autofarm gear (not the dealer). We did the 24hr survey and that sorted it out! Thinking it might be worth doing that each year. Cheers

Is it really a 24-hour survey or a 30 minute? Our shows 1800 seconds (30min).
We do one every spring before the rush.

 

[carlh]

Is it really a 24-hour survey or a 30 minute? Our shows 1800 seconds (30min).
We do one every spring before the rush.

You're probably right, ours seemed to have locked in within at least the first hour or probably sooner but did a full 24hrs on their recommendation, but probably overkill.