Farm vehicle interference on 2.4?

[martin collins 1]

One of the sites i fly at is in among various fields of crops which at this time of the year are being harvested, there also seems to be a surprising number of `loss of control` incidents at the patch at this time. Before all the Spektrum bashers get going it is spread among several different makes, including Hitec, Futaba and Spektrum. I witnessed one a couple of days ago, we have a farm track at one end of the strip and a large nicely built scale model was banking over the track as a large tractor and two cars drove under it. The plane then turned over on it`s back and dove into the field just beyond the vehicles, not a stall, there was plenty of airspeed but it was as the convoy passed underneath, the radio gear was Hitec in this case. Has anyone else found interference problems with large farm vehicles in the area?

[Brian Dorricott 1]

Not sure but the vehicles may have been communicating on Bluetooth which is on 2.45Ghz ? Maybe just enough to desense the receiver as it flew over .

[Peter Christy]

All equipment operating on 2.4GHz is subject to the same rules and regulations as we are. Compliant signals should not cause any interference.

Having said that, if someone is using illegally high powers, or something like the old analogue video systems at high power, then it could - in theory - block "our" signals.

However, even in these circumstances, the "fail-safe" should still work.

A more likely scenario is that a new microwave link has been set up in your area. These are very narrow beams providing point-to-point communications for various telecoms applications. Inside the beam, the signal level can be very high indeed, quite possibly enough to disrupt the micro-processors in the receivers, and thus prevent the failsafe from operating.

This has been known about since the days of 35 MHz! The solution then was to wrap the receivers in silver foil, which proved remarkable effective!

Note that I said wrap the receiver in foil, NOT the aerial! Not so easy on 2.4 GHz.

Did all these failures occur in the same patch of sky? If so, you've probably strayed into a microwave beam!

It could also be the someone operating a new high power radar system. This would have a wider spread. Any airports nearby? There have also been reports of the government testing out "anti-drone" measures, though these are often announced before hand - though not necessarily in places where we would see them! SteveJ of this parish seems to have some insight into these tests, so maybe he will be along shortly to comment.

In short, it is unlikely to be a problem caused by any legitimate users of the band, but more likely a high intensity (and out of band) signal that your club members had the misfortune to stray into.

All model control equipment is built "down to a price", and is unlikely to be able to deal with a highly disruptive out-of-band signal, should you be unfortunate enough to encounter one. If you want equipment hardened against such (rare!) interference, be prepared to pay a LOT more money for it!

--

Pete

[Brian Dorricott 1]

Also any high powered WiFi repeaters ( illegal) in the area maybe , guess what frequency they are on yep ! 2.4Ghz .

[Andy Stephenson]

Radio hams are allowed to use considerable power on the 2.4GHz band, could there be any operating in the area.

[Richard Wills 2]

I have no idea on the radio interference at your site, we do have a microwave tower on the next hill from us which from time to time does cause problems in a specific small part of the circuit, mostly momentary failsafes for most brands of radio, total lockouts for one in particular.just something you can't do much about.

I would be seeing this as a safety warning about something else though. Surely the practice of overflying vehicles not under your direct control has just been demonstrated to be a potential risk which needs to be mitigated at your site?

[Chris Walby]

Back to the OP, the amount of technology now imbedded within farm equipment is very significant and their problem is to communicate over challenging distances with poor existing infrastructure (lack of mobile signal) probably makes things worse for them.

I would expect combines, tractor trailers and even baillers to all be processing real time crop yield information and relaying it to the farmers HQ.

Why would it be an issue to the manufacturer or the farmer if they generate interference, 99.9% of the time its on their land and no one else is about...apart from us.

Now if we could prove it then we would have a case, but how expensive is that to achieve?

PS - we have a radio interference issue at work, we have a licence and one of the channels is almost continually disrupted by an external party. Short term we have stopped using it, long term it will be investigated and legal action may follow to resolve the issue....how long and costly is that really going to take?

[martin collins 1]

There is no housing close by so wifi boosters should not be a problem, we have a chicken farm with a couple of wind turbines on it up one end which is about 1/2 mile away, some have reported issues if flying too far out from the strip at that end. The other end has the farm track which has a shipping container placed alongside it for club storage, most problems have been reported at this end. I haven`t had any issues yet, my gear is Spektrum but as i mentioned the problem seems to be across all different makes of equipment..........

[Peter Christy]

Posted by martin collins 1 on 04/09/2020 11:35:29:

...most problems have been reported at this end.

Sounds to me more like a microwave link or radar, and inadvertently flying through the beam. It might not be active all the time.

Remember that 2.4 GHz is an unlicensed band, which means we have no protection against other users - as long as they are operating legally! Proving they are not operating legally could be tricky. In any event, pure RF interference on 2.4 GHz should still allow the failsafe to operate normally.

The incidents you describe seem to indicate that the failsafe did not operate. That indicates either 1) power loss to the radio or 2) something breaking directly into the processor.

1) could explain a single incident, but not multiple ones, which leaves 2). That is likely to be either a radar signal, or other high powered microwave transmission.

--

Pete

 

Edited By Peter Christy on 04/09/2020 12:41:17

[Former Member]

[This posting has been removed]

[Denis Watkins]

Just to add, we have a scanner at my place, and typically, in the pilots box, we detect 11 - 12 sources.

These are stronger, or equal to our transmitters, But

We have no issues and have had no issues.

The Military used 2.4 long before we did, and the band was designed and developed to operate in the " crowded environment.

Which it does quite well

As per previous posts, 2.4 does not work well below designed voltage and modelling does benefit from both range testing and failsafe setting

[Ron Gray]

I’ve started to use 868MHz gear on some ‘planes as we’ve had some ‘strange’ interference issues on our site over the last couple of years. For belt and braces I’ve got some setup with both 868 and 2.4, the latter acting as redundancy.

[Mike T]

Posted by Steve J on 04/09/2020 13:43:24:

There is a design for a 2.4GHz scanner over on Mode Zero.

If you do decide to make one, I would suggest using the nRF24L01 with the long range antenna rather than the basic one.

Thanks for those links - I've commissioned the Club computing whizz-kid...

[Phil Green]

Posted by martin collins 1 on 04/09/2020 09:10:27:

a large nicely built scale model was banking over the track as a large tractor and two cars drove under it. ... it was as the convoy passed underneath

I wonder if the tractor/harvester has a video transmitter on board? A wireless safety camera used to keep an eye on the bailer or whatever?

[Geoff Reynolds]

Posted by martin collins 1 on 04/09/2020 11:35:29:

There is no housing close by so wifi boosters should not be a problem, we have a chicken farm with a couple of wind turbines on it up one end which is about 1/2 mile away, some have reported issues if flying too far out from the strip at that end. The other end has the farm track which has a shipping container placed alongside it for club storage, most problems have been reported at this end. I haven`t had any issues yet, my gear is Spektrum but as i mentioned the problem seems to be across all different makes of equipment..........

Hi Martin and everyone on here

There has been a suggestion in the past that the caravan site nearby has a wifi booster, although I don't think that has ever been followed up for fear of upsetting the landlord.

The problems existed before the two nearest wind generators were installed, however, there is that much larger wind farm not that far away across the fields to south east!

Comments have indicated that the problem has been worse since the new chicken sheds went up, but this radio problem has coincided with the end of lockdown, and the increase in farm vehicle traffic this harvest season.

It has been hard to pinpoint but the problem does seem to be both ends of the field, not really north or south and not higher up, nearly always when the model is within a house height or two of the ground. Which would indicate some sort of signal passing fairly directionally along the 'normal' takeoff and landing strip direction, some few metres outside the southern boundary, but extending to maybe 50 - 100 metres east and west from the field edges at around house height.

I'm sure if a survey of all members who've lost planes or had 'glitches' there would be overwhelming evidence that it mainly occurs in this area. Most others are from inexplicable and unaccepted thumb or orientational causes!

The other query which has happened twice recently is the use of mobile phones. Are newer models becoming stronger? A member lost control in the suspect area, but higher up and regained it before disaster, when another member, (not flying, but standing on flight line) answered a call from a family member. The plane temporarily lost bind it seemed and as the member using the phone moved quickly away, the model recovered thankfully.

Secondly, the same evening of the crash mentioned, I was in the pits setting up a model whilst a member was on a mobile call not far away. My Spektrum gear (which has never given trouble before) wouldn't bind until the call was finished! Following the call end, I retried and the model bound immediately and I flew with no problems.

I know it's tempting fate to say I've never had a problem with Spektrum, although our chairman and I did comment on an incident about 5 years ago when he was flying one of my models and he lost control in a similar area to this recent model destruction, but managed to salvage it to land with little damage in a ploughed field. The flashing Rx light indicating a brown-out loss of signal! The Rx has never again suffered this.

Yes, there is something around our field and with each new incident it becomes more worrying that the next will be you or me.

[Former Member]

[This posting has been removed]

[Martin Harris - Moderator]

It's interesting that two of our members (sadly one has now deceased) with the same type of radio - not the usual suspect by the way) have apparantly suffered multiple issues on a particular line and height close to our field which would suggest a possible microwave link - although nobody else seems to have encountered it and I tried flying in the reported area intensively with no indication of any problems either physically or with signal strength or quality (packet loss) issues being recorded with my own system of choice.

They have backed up their findings with telemetry results indicating signal issues - one possible factor could be that both of these pilots tended to fly at less popular times so perhaps these links only transmit for limited and/or specific times. Alternatively, perhaps their receivers are more prone to microwave issues than others.

[Geoff Reynolds]

Posted by Steve J on 05/09/2020 14:26:31:

Posted by Geoff Reynolds on 05/09/2020 14:07:13:

The flashing Rx light indicating a brown-out loss of signal! The Rx has never again suffered this.

A brown out is a loss of power. On DSM2 Spektrum receivers, the orange LED will flash slowly to indicate brownouts (resets). Some Spektrum receivers have a red LED that flashes to indicate holds (failsafes).

So that's a loss of power to the Rx from the battery? Momentary due to high demand on the flight battery presumably. Nothing to do with signal loss, which might indicate the Tx was low on power? But at least two of the big crashes have been on IC with definitely good Rx battery condition checked after crash. Most electric's have been total destroys so very little left to check! Modern servos do use more power I'm told. I've been using a DX6i for many years and have a newer DX6iX and it was only whilst reading the manuals to find out how to program elevon mixing just the other night that I realised that there were a number of different power settings available on both. There's EU, US and French. I'm wondering if some might be set wrong.

[Geoff Reynolds]

Another model lost yesterday, almost exactly same place as the lovely scale one. Very similar circumstances, began to roll, continued into spiral dive and no amount of Tx input could solve it.

Model found with (twin) Spektrum Rx's lights flashing, and ailerons doing slow, to full deflection movement, reset to flat, repeat.

On re bind, everything worked correctly. Range test passed perfectly, battery still with plenty of power.

In conversation afterwards it transpires that another member plugged a battery into his electric model the other day ready to fly, but because he wanted a drink first, left it, on the ground, in the pits with the Tx's motor isolation switch on, so no power to motor, but everything else live. He then noticed the prop jerking back and forth and the control surfaces cycling.

We are going to log as many crashes (hopefully very few) as we can with time, position, type and radio equipment to see if a pattern emerges.

The farmer has confirmed there is no electrical equipment in any of his vehicles and the wifi to the caravan site is very poor strength.

A test has been conducted by a member with a scanner and in the hour or so he was on the field, there wasn't one signal detected!

Now this is getting scary!

[Frank Skilbeck]

2.4 is a digital signal, so any interference to the signal should result in the receiver going to the fail safe setting, the cycling of servos and pulsing of motors is not indicative of the radio signal being interfered with, but maybe a more general electromagnetic interference affecting the signals from the receiver to the ESC and servos. Or affecting the electronics in the transmitter that then passes those onto the receiver.

[Peter Christy]

I refer you to what I said earlier: This smacks of radar or microwave link interference. Such interference is not on 2.4 GHz, and won't show up on a 2.4 GHz scanner. It works by directly interfering with the processor in the receiver, which also prevents the failsafe from operating.

I would suggest contacting Ofcom, copying in the BMFA. If I am right (and I think I am) finding the source of the interference will not be achieved with the kind of equipment most people can afford!

--

Pete

[Geoff Reynolds]

Thanks both of you for these comments.

We are going to be getting the BMFA involved and, because we have a number of ex telecomms engineers as members, with some very high levels of skills in this area, we are putting together a case for Ofcom, but we need to get some documented evidence of times, dates, equipment and such like to make it a convincing bunch of evidence and not a load of unrelated pilot errors, equipment failures or inadequacies.

For the moment, the best brains we have are foxed.

[Geoff S]

These sorts of problems can be worrying. We can accept (albeit reluctantly) that most of our model disasters are self-inflicted but with the best care in the world you can't allow for serious external interference.

When I flew at RR(Hucknall) some years ago there was one 35Mhz channel whiich was banned because of several unexplained crashes. In the end we found that anglers on a nearby pond were using RC bait boats running on 35Mhz on the suspect channel. They were being sold by a manuacturer and the anglers were unaware of the implications. I think the manufacturer was fined and stopped.

Having spent the best part of a year building a model it chills the blood reading about your problems. I hope they're resolved soon.

Geoff