Advice on a 2.4 GHz radio

If my cell phone is very close to my TX it will make my plane go crazy when it rings, and for some reason it's even worse when it gets a text message. Turn on your TX, turn on your plane, and put your phone down next to the TX. Then call your phone and see what your plane does. It's not strictly radio interference, it's the cell phone signal getting in to the whole TX and making it transmit garbage.
The local police dept's mdt's will interfere with the plane itself (not the TX). If my plane is on the ground near the back of a patrol car it will jerk and twitch with each transmission from the mdt (and they transmit more frequently that you think, not just when a message is sent but there is a "received" message it sends back for every message it receives and they also pumps gps data back to dispatch through the mdt system).
All of these interference problems drop off radically with some distance.
Steve
Reply to
Steve
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I guess I've been lucky. My normal procedure at the field is to wear my cell phone on my belt and turn the speakerphone 'on', so if the wife calls I can reach down and open the flip to answer and talk without taking my eyes off the plane.
Using a 9C transmitter, FWIW...
Reply to
David Hopper
On Thu, 20 Sep 2007 17:08:25 -0700, Steve wrote in :
Great answer!
It's a very simple and safe experiment.
You might try this with the plane out a little distance, too, and with the antenna collapsed or mostly collapsed. Do a range check first, then test the plane with the cell phone ringing on your hip or in your pocket--wherever it would be most naturally when you have it with you.
(I don't have a cell phone, so it's a moot question for me.)
That makes sense to me.
Marty
Reply to
Martin X. Moleski, SJ
On Thu, 20 Sep 2007 21:48:57 -0400, David Hopper wrote in :
That's important information.
Sounds like you have shown that interference is NOT a problem for you.
If you ever do get a glitch when the phone rings or you're talking on it, probably all you have to do is put the phone on the ground and take a step or two away from it (worst case scenario). It shouldn't be a big deal if you've mentally rehearsed the drill.
Marty
Reply to
Martin X. Moleski, SJ
wrote in
Good advice, Marty.
Not all transmitters are susceptible to interference by a nearby cellphone. In fact, I would "guess" that the majority of transmitters will not be affected by cellphones in the immediate vicinity. However, the flying field, with a model in the air, is not the place to test this hypothesis.
If you absolutely must have an active cellphone on your person while flying, perform some tests with the model on the ground first. After all, we are looking for problems with scrambled Tx programming, not in the model, so it does not have to be flying for the test to be performed accurately.
I didn't know that you were a licensed ham, Marty. Good for you.
Ed Cregger, NM2K
Reply to
Ed Cregger
Actually, you need to turn off your cellphone when leaving it anywhere withing a few inches of a software programmable transmitter.
IIRC on a futaba set, it is capable of wiping the EEPROM on a TX even when the TX is SWITCHED OFF.
The case I recall was somene who tossed his transmitter and his cellphone into the same box and went flying..to discover that his model memories were complete garbage.
Another anecdotal story concerns a man who was flying a glider up high with his cellphone in his breast pocket, where he was also holding his transmitter..the phone rang and the model went wild.
None of these are proven beyond all reasonable doubt: Could be coincidence, BUT
- when you are a LONG way from the nearest tower, your phone does use a LOT of power to try and reach it.
- VERY high strength RF fields can and do interfere with unshielded digital electronics.
I am sure I have related the case of a certain person, who both ran a PC clone assembly factory, and was troubled by a loathsome neighbour - dope dealing 3.a.m loud music guy..
I suggested to him that he acquire a very powerful shortwave radio, hook it up to a signal generator, and swamp the guys hi-fi.
He acquired from an unknown 'mate' an ex police base station, and when he tried it in his assembly area, 'every PC rebooted'
It was also entirely successful at rendering his neighbours HIFI completely unusable.
All electronics is a receiver of some sort. Normally the signals are low, and the effect is minimal, but make the signals high enough and almost anything will perform weirdly.
With cellphones, keep them at least a few feet away from the transmitter and receiver when active, and do not pack a switched on cellphone with a transmitter, on or off.
Reply to
The Natural Philosopher
On Fri, 21 Sep 2007 02:34:03 -0400, Ed Cregger wrote in :
One variable that we haven't discussed is the variety of cellphones that people use.
Do different models have different power levels?
Do some phones transmit at different power levels in different conditions?
I don't know anything about that at all.
Just a question to think about. And something to note if people are reporting the results of their field tests. It seems conceivable to me in the abstract that some brands and models might cause more trouble than others.
Heh heh. Too late! Some folks have already embarked on the experiment! :-O
Agreed.
And I hope that folks will be gentle with each other in discussing this at the flight line. I definitely want to have a safe and sane flight environment, but I equally definitely don't enjoy the multiplication of rules and arguments about rules if there is some other way to achieve the same end. I prefer persuasion to coercion.
I just took the lowest and easiest test so that I could fly on 6 meters. I enjoyed the experience of studying very much--but I dawdled along the way and my book became obsolete in the interim. I passed the test with about 85% on the exam, but if I had studied the right book I would have gotten 95% to 100%.
Live and learn!
Marty
Reply to
Martin X. Moleski, SJ
On Fri, 21 Sep 2007 10:44:10 +0100, The Natural Philosopher wrote in :
Other people have reported similar problems. I saw some discussion of that while searching for information about interference the other day.
That all sounds plausible to me.
Back in the 60s, I could watch the output from my Galloping Ghost transmitter on my TV. I don't remember what channels I was on, either with the TX or the TV, but it was very instructive to SEE and HEAR the output from the transmitter. It helped me to understand how the radio was driving the receiver and servos. It was very clever.
Makes sense.
Marty
Reply to
Martin X. Moleski, SJ
in :
Not significantly, no.
All phones transmit at different power levels in different conditions.
:-)
IIRC the main trouble was with a particular FUTABA transmitter, that got its memory wiped.
d.
Indeed. The balance of probability says that if you switch the mobile OFF or don't take it to the flight line, its OK.
And it will be YOU that gets shot down by YOUR phone. Unless you are engaged in a close embrace with another pilot when your wife phones up ;-)
Reply to
The Natural Philosopher
Ok, so just to clarify.
This is a problem with not only the new 2.4g radios, but our old one as well
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Reply to
Slent thndr
On Fri, 21 Sep 2007 21:31:12 -0500, Slent thndr wrote in :
I haven't heard of any cell phone problems with the new radios.
The problems I've read about are all with current equipment.
Marty
Reply to
Martin X. Moleski, SJ
I think, having just read through all that, and understood at least som
of it, that you can be pretty certain that there is a possibility tha there may or may not be a problem with some TXs, either on the ol 35/72 Mhz frequencies or 2.4, but that there is a general concensu that nothing is definite. So, in essence: Yes
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Reply to
DoctorFloyd
The frequency of the R/C Tx is not the issue, nor is the band.
The problem is that some foil traces and bits of wiring inside of the Tx can be of the proper (wave) length to "couple" to the cellphone's RF output. USA Cellphone's are high enough in frequency (800-900 MHz) that the RF output frequency is a pretty good physical match in wavelength to various random lengths of conductors in your Tx encoder's circuitry. This mean that stray voltages are introduced into the R/C Tx that can foul the Tx's programming. I hope that made sense.
So, to boil it down even further, it is the R/C Tx's encoder section (non RF) that is being influenced by the cellphone's RF output power, however small it may be.
Yes, the only way to be sure that your system is not affected is to perform various tests with your cellphone in close proximity to your R/C transmitter. Even then, the best policy is to leave your cellphone back at the flightline, or in your vehicle if you must leave it on. Various two-way mobile shops can fix you up with a horn beep alert for your vehicle if you absolutely must know when your cellphone is receiving a call.
Ed Cregger, NM2K
Reply to
Ed Cregger
"Ed Cregger" wrote
I thought that there was/were incidents reported where the transmitter's memory for the different models were scrambled.
I agree with your basic analysis of the components coupling to the cell's output, but I think the possibility of the coupling to the memory modules, and flipping some of the 0's and 1's within memory chips in the storage areas.
Of course, there are those types of memories in different locations in the transmitter.
Reply to
Morgans
I swear that I heard about cell phones using "GMS" technology causing memory flips in transmitters a few years back. I didn't pay that much attention because that particular format was in use in Europe and I don't fly there.
Jim
Reply to
Six_O'Clock_High
"Six_O'Clock_High" attention because that particular format was in use in Europe and I don't
GMS is here in Texas. I meant to do tests with cell phone and TX this weekend and I got to flying and forgot! mk
Reply to
MJKolodziej
"Six_O'Clock_High" attention because that particular format was in use in Europe and I don't
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Roger that.
What I am proposing is that we test our equipment ourselves, with the equipment that we have, and then not worry about it if the results are favorable - meaning no noticable corruption has occurred.
I am a radio nut, like most R/C flyers. Over the years I have noticed interactions with various transmitters (of all kinds) and consumer electronic goods. Who hasn't? Rather than trying to set banning rules that are rigid in an ever changing world of rapid advancement in electronics, let's be reasonable and see if our gear "of the moment" reacts negatively, and then pursue our own avenues of prevention, instead of making gradiose proclamations that this or that brand of radio is not safe or is undesireable.
No, I'm not saying that you are a proponent of this mindset, Jim. I'm speaking to the group in general.
Ed, NM2K
Reply to
Ed Cregger

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