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Old 08-19-2018, 09:20 AM
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Radio interference - Futaba FASST only

For the past 2 months our field has been haunted with radio interference that affects Futaba FASST radios only.

Futaba FHSS radios fly with no problems, as do Spektrum /JR, Hitec and even HK radios. Obviously all these radios use the same FHSS technology.

Our field is located in a park, near the ocean with no houses around it. There is however a cell tower nearby which we suspect may be the culprit. Had technicians come and check, and supposedly took care of "maintenance issues" but the problems are back again.

We bought a portable Spectrum Analyzer, but we have not been able to isolate the problem signal. It seems that the signal is NOT always on. We detect a constant signal from a wifi network, but this does not affect the radios - they work around it.

The interference is random, and it affects only one SPECIFIC area of the field, at 1 of the 2 runways at LOW ALTITUDE (under 50 feet) when on landing approach. Planes that got "hit" on approach did not have any problems when flying higher above the same area.

Transmitters used are mostly Futaba FASST 7C. Receivers used are mostly Futaba 617 and some 607's as well. Some people even use FrSky receivers. Users are both newbies as well as some of the most experienced builders, so it seems that installation and operation does not play a role..

We are at a loss as to the cause of this situation. People are screaming about contacting the FCC to investigate. But before we go that route, we would like to try to resolve this problem locally.

Any ideas/ suggestions? Thanks in advance.
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Old 08-19-2018, 09:45 AM
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First, we operate under Part 15, which means that you will have little recourse with the FCC. Basically unless it is shown to be malicious interference there is nothing the FCC will do.

Second. How many people are having this issue? Those that are having issues, have they ever had their transmitters serviced?

What happens when the interference happens? Do they lose control and the model reacts erratically, or do they go into hold? Do any have a failsafe set (channel 3 only when using the 617)?

Are they all the same power type? gasoline/nitro/electric?
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Old 08-19-2018, 10:24 AM
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Airplanes with the issue are usually 40-60 size nitro planes, and similar size electrics. Larger gas airplane pilots use JR/ Spektrum equipment or Futaba FHSS with no problems.

They have fail safe set on throttle channel, as they claim that's the only one available for this receiver (I am a JR/ Spektrum guy.)

while flying wings level on landing approach., the interference causes the airplane to suddenly turn to one side, in what it seems to be an aileron turn. It stays locked in the turn and usually crashes. Some pilots manage to fight it for a moment, only to lose it again.
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Old 08-19-2018, 10:53 AM
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See, here's the thing. Outside interference will normally cause a lockout/failsafe. It rarely, if ever, causes sudden action of a single control like ailerons. It is also interesting that the SFHSS radios work fine since FASST/FASSTest is generally considered the more robust protocol. In addition, everywhere I am familiar with the larger plane guys use FASST/FASSTest while the SFHSS is used mostly on smaller planes.

Again, how many people, not planes, but individual pilots, are having this issue?? And are they ALL flying the 7C? If not, what is the mis of radios?
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Old 08-19-2018, 11:06 AM
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Issue like that happened at a field nearby. Specific location was termed the triangle of death. It turned out to be a microwave transmission system atop a nearby bldg. It affected all 2.4ghz radio systems though.

Go to Google maps and see if you can spot any antennas or dishes atop any bldgs within the affected flight path
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Old 08-19-2018, 11:40 AM
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We had a similar non-brand specific problem at our field. Six planes were lost in about a two week period. In one instance two planes were being flown and they were both hit and crashed at the same time. It is a random occurrence and most of the time we are OK but it gives an uneasy feeling when flying. We also have a cell tower about 1/4 mile away. I don't know that that is necessarily the cause of the problem
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Old 08-19-2018, 12:11 PM
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Almost all radios affected are Futaba 7C. There are 2-3 other Futaba PCM radios with FASST modules on them. The latter are advanced 9-channelFutaba radios that fly jets in other fields with no problems.

Overall, there are 12-14 pilots who experienced the problem.

As for microwave transmission, it is a possibility we are now looking into. It is VERY directional. It may come from the tower (the affected area is in line of sight), or from another commercial building close to the field.
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Old 08-19-2018, 01:55 PM
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Quote:
Originally Posted by Cryhavoc38 View Post
Issue like that happened at a field nearby. Specific location was termed the triangle of death. It turned out to be a microwave transmission system atop a nearby bldg. It affected all 2.4ghz radio systems though.

Go to Google maps and see if you can spot any antennas or dishes atop any bldgs within the affected flight path
How did you determine it was a microwave transmission?
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Old 08-19-2018, 02:36 PM
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Originally Posted by LIpilot View Post
Transmitters used are mostly Futaba FASST 7C. Users are both newbies as well as some of the most experienced builders
if they use it to play the simulator there might be a broken SMD diode on the main board.
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Old 08-19-2018, 03:25 PM
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Do all of these 7C transmitters have the same GUID ? How old are they ? This is the only common thing I can imagine. Very early 7C transmitters had a problem. But you say there are a bunch of 9 channel radios with modules. Very old.

You can check and see if any of the 7C will operate someone else's receiver that it is not linked to.
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Old 08-19-2018, 05:22 PM
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Originally Posted by Four Stroker View Post
Do all of these 7C transmitters have the same GUID ? How old are they ? This is the only common thing I can imagine. Very early 7C transmitters had a problem. But you say there are a bunch of 9 channel radios with modules. Very old.

You can check and see if any of the 7C will operate someone else's receiver that it is not linked to.
Good suggestions. With the module radios it is also possible that the module plugs are messed up. Especially if they have not been plugged in and out lately. Corrosion can build up and cause a weak signal. Just odd that it is hitting a variety of FASST radios. Something is off here.
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Old 08-19-2018, 06:08 PM
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Thanks for all the suggestions. We have looked into the most common Futaba problems with the other Safety Officers at the field, especially the common GUID issue of the first 6C and 7C radios. Each of us has a minimum of 25 years in the hobby and are able to inspect equipment setups thoroughly. When in doubt we ask pilots to send their radios in for check up/ service.

All these FASST radios worked fine for many years - until June. The problem is random and is driving us crazy. The most puzzling thing is why the interference affects only FASST systems and not anything else. If someone was trying to shoot us down purposely with a "drone killer" he would affect all 2.4 systems, not just FASST radios.

The prevailing theory at this point is that the "death zone" gets hit with a strong signal, a burst that blankets the spectrum and overwhelms the FASST system while it tries to hop to a clear channel. Unfortunately the signal does not stay on for extended periods so that we can identify it.
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Old 08-19-2018, 06:19 PM
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Except if that were the case the RX would hold last good command or go into failsafe. If that is not happening then it is not an external source. Honestly, if those radios have never been in for a check up that could be part of it. The 7C is a Golden Oldie in the 2.4 world. But it is an oddity.
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Old 08-19-2018, 08:23 PM
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Quote:
Originally Posted by LIpilot View Post
How did you determine it was a microwave transmission?
I want involved in the detective work but a couple field officials canvassed the nearby bldgs and found that there was a line of sight microwave transmitter atop a nearby bldg which transected a corner of the airspace where the anomalies would occur. On top of that the system was not in use 24x7 but only when data was needing to be transmitted. Tbh I do not remember what was done to remediate the issue. In the Bellevue Kent Renton etc 3d thread on rcgroups has a couple pages outlining the issue and what was done about it. As judge has said, our TX and RX systems are not protected by the FCC and are subject to receive interference.
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Old 08-19-2018, 08:38 PM
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I want involved in the detective work but a couple field officials canvassed the nearby bldgs and found that there was a line of sight microwave transmitter atop a nearby bldg which transected a corner of the airspace where the anomalies would occur. On top of that the system was not in use 24x7 but only when data was needing to be transmitted. Tbh I do not remember what was done to remediate the issue. In the Bellevue Kent Renton etc 3d thread on rcgroups has a couple pages outlining the issue and what was done about it. As judge has said, our TX and RX systems are not protected by the FCC and are subject to receive interference.
2.4 gig frequencies are shared...... but the 72 MHz frequencies are specific set for RC flight
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