r_kopka

Interference is a very real danger in this case.

RX usually have a regulated amplifier as first stage behind the antenna to adjust to the signal strength regardless of frequency ! Thereafter is the mixer which creates the lower frequency (the same for every Quartz) which is then amplified in a very narrow band. This mixer should get a rather constant signal level independent of distance from TX.

If the plane flies in a distance directly above another TX the regulated amplifier will adjust to the TX nearby and the correct TX signal will not get the amplification it needs. That is not so much a problem if the TX are on different bands (e.g. 27MHz / 35MHz), as there is some kind of wide bandpass right after the antenna.
If the TX are next to each other this problem doesn't occur.

RK

TexasAirBoss

My Feedback: (22)

What about the dreaded 3rd wave ? Was anyone else on ?

Redback

A receiver does not know if it's over, under, left, right or otherwise oriented towards a transmitter.

All it sees is the field strength and polarity of the received signal. Since directly over a dipole is the point of lowest field strength I remain unconvinced that this crash can be attributed to flying over a transmitter.


Terry

r_kopka

But we can't know the direction of the "field" antenna - could be anything, ditto for the controlling TX.

RK

Crashem

I got to go with Redback on this. I did a little experment last night I took 1 Rx on Ch 22 and two tx's one on ch22 and one on ch11
I hung the model from the ceiling and placed the TX on ch 11 directly underneath it it was rock solid no interference I even turned off the TX on ch 22 the servos moved one then remained slient. I realize this test isn't conculsive but if flying directly over another TX regularly caused interference I think we would have heard about this. Hopefully you will go back with an open mind and try to find the real cause of the crash

edh13

My Feedback: (9)

RF problems or not, it's beside the point. I don't know any FOOL who would turn their Tx OFF to retrieve a dead stick acft. And I don't know any FOOL who would fly a low slow pass over someones head. You said it was at a "meet". There had to be spotters.

airbatic

Aw come on man admit pilot error or you got distracted by him running into the field.

88

Kraus

rlipsett

The only way I see for this to happen would be if tx crystals were swapped or if the radio has not been serviced in a awhile and you have the tx splashing over onto other frequencies. I have no way of proving it but it might be a possibility.

50%plane

My Feedback: (5)

Pfine,
Are you still with us? Are you going to defend yourself of the charges of being the fool? Why do you think that the other guy is the fool? Have you serviced your radio lately? Were you flying with a radio that meets current standards? Was the other guy? What meet was this at?



Bye the way, you had a very very nice plane! I hope that you will repair it.

Have a nice day

UKWes

Here in the UK our governing body the BMFA state:

quote](o) Care must be taken at all times to avoid overflying operating transmitters. Pilots should stand together and should not be allowed to wander over the flying area when operating transmitters. Clubs should take action to prevent operating transmitters being taken out on to an active flying area when, for example, models are being retrieved.[/quote]

This is because even though you may be on different frequencies that would not interfere when the TX are close by, the harmonisation of the signal can interfere if the plane is closer to a TX with a different channel.

If you must walk out to the field to retriebve your model with the TX on, then leave it in the pits close to the pilots box. Either way, the throttle should be shut down and you should be able to see a model whose engine is running by blipping the throttle, unless you land miles away from where you are standing.

Montague

Signal strength from a transmitter drops off as the cube of distance, if I recall correctly.

So, if you are standing at one end of the runway, and your plane is at the other end, and gets close enough to another TX, yes, this kind of thing can easily happen.

If the two TX's are right next to each other, then no, it won't happen. But that's a totally different situation.

I do wonder how the pilot came to pass low over the head of a guy on the field.

Either the guy who walked out didn't call that he was walking on to the runway and wasn't seen, or the pilot made a low pass when he shouldn't have.

At most events and fields I've flown at, calling out "on the field" before going to get an airplane is manditory. And, when you hear that call, you break off any low passes and do not fly directly over the head of the people walking out there. Not to prevent interference so much as to just avoid the chance of something stupid happening.

âûñøåå îäíî

He said he was doing a "slow pass" what do you guys think about a stall?

Redback

I did a similar test to Crashems before his post. Here's my results:-

Transmitter A JR2610 on 36.530MHz
Transmitter B JRX388S on 36.430MHz
Receiver A JR R700 on 36.530MHz (in SIG SE)

Firstly I placed Tx A on the ground with the antenna vertical, and Tx B similarly 20 metres away. I then walked the plane over Tx B looking to see if there was any interference. After a number of passes, some with the top of the Tx antenna touching the plane none was detected.

I then placed the plane on the ground and walked around it with the Tx, staying within 2 antenna lengths, and by positioning the Tx in various ways tried to get a reaction from the Rx. None was detected.

I then moved Tx A to be 50 metres from Tx B and repeated the above with similar results.

Next, with Tx A still at 50 metres I tried to get Tx B as close as possible to the Rx. When I got the Tx within 50mm (6 inches) of the Rx some minor servo noise was heard, however no significant control surface movement was seen. Once the Tx was 50mm from the Rx it became quite. With Tx A back at 20 metres it was not possible to get Tx B close enough to the receiver to interfere.

All the above were done without the engine running, I wasn't brave enough to wave the model around with a 12 X 4 whirling around[X(]

Terry

RC-Captain

Nice experiment, but no disrespect you wasted your time. If what was described as the cause of the crash is true , there wouldn't be any clubs.

Good Luck

Columbo

My Feedback: (9)

I noticed the plane has a gas engine. Maybe he should consider his receiver, ignition battery distance
as a possible cause for interference.

Greg

N1EDM

My Feedback: (2)

Just a thought, but we're all assuming that everyone's radios (both TX and RX) are in perfect working order. What if one or the other, from either flyer, was out of tune?

Just a thought....

Bob

BasinBum

My Feedback: (2)

I think close proximity could very well cause another plane to glitch. There are a lot of unknown factors here, condition of recievers and transmitters, and directions of antenas for a few. While pilot error, air currents from the grass to pavement, stall speed could all be factors everyone is an automatic RF expert when it comes to this case, very amusing.

Probably for the same reason you are statistically more likely to have a car accident near your home, that's where you do the most driving/flying.

Maybe at your field but that is a silly "rule" and your example doesn't happen often enough to warrant it. I always remind people to leave the TX so they will have two hands to carry back the plane/parts when they make the walk of shame.

I usualy like to call BS when someone makes excuses for a crash and, while the guy walking out with a TX isn't conclusive by any means, I'm not so sure we can rule it out altogether. Either way it's a regretable loss of a beautiful plane.

RC-Captain

Then the cause of the crash would be a radio not being tuned, not flying over another persons radio.


I fly approx. 15-25 minutes in the air and taxi to leave ground in about 10 seconds.

The sometimes obvious reason for crashing near the ground is just poor judgment on how to land. IE. depth perception, speed, dumb thumbing etc.

And I'm not an expert on radio frequency , I have proved this myth 2 years ago with the 5 or more radios and transmitters I have.

Good Luck

twistr

My Feedback: (4)

Maybe at your field but that is a silly "rule" and your example doesn't happen often enough to warrant it. I always remind people to leave the TX so they will have two hands to carry back the plane/parts when they make the walk of shame.

Basin: Our club is very serious about safety. The fact that one should ALWAYS have control over the plane is a very serious safety factor. I do not believe it to be "silly" as you call it. You know, you say "it doesn't happen enough to warrant". Well, it only takes once, doesn't it???

BasinBum

My Feedback: (2)

Well you were speaking for the good ole USA and not your club. I was pointing out that it isn't a universal rule in this country and I doubt your club has it in writing so it's just something you think is a good idea and I disagree.

As for RC-Fiend, I won't bother to make a counter point because if I said it was light outside he would undoubtedly say it's dark, and it's somebody's fault it's dark to boot.

nicadflyer

Interference is probably what happened. It sounds like the plane was very close to the person on the field. This could cause planes receiver AGC to lock down (Lower the gain) the first RF amp (before the mixer). This amp is a wide range (the whole frequency band) amplifier. The transmitters signal was probably replaced with noise or the signal from the other trans. This should have lasted only for a few seconds, but that's all it takes.

Also, the signal leaves a dipole (or transmitter) antenna at 90 degrees and the field is shaped like a doughnut.

Nice looking plane. Too bad this happened

N1EDM

My Feedback: (2)

I don't think that we should be so quick to point the finger at pilot error here ... someone with the experience (and tenacity) to spend 8 months building a Scale plane of this calibre would (presumably) have a lot of flight experience - perhaps more than many of us on this thread. It can't be ruled out, but i'd put it very low on the list of probable causes....

I'd be more inclined to think about the equipment and field conditions.

Just my $.02

twistr

My Feedback: (4)

OK , I should have not spoken for all of USA, after all, it is a big country. Let me re-phrase. I was speaking for my own club.

And don't assume to know what my club has or does not have in writing, you know nothing of my club. The bottom line is we disagree on this. So let's agree to disagree and move on!

Balsa Master

it would all depend on the wavelengths and ampletudes of the radio... if by some freak chance the radios were offset to a point where there frequencies overlapped at slightly at that close of a range it may be enough to cause a plane to go down... ive controled my 52 wit ha 72 before... granted its not a pretty sight and id never fly liek that... the radio will still effect the receiver even on a significantly widder band so long as the tx is in VERY close proximity to the plane.

i say this because all radios will interfear. turn your tx on near your tv, under the right surcumstances (presuming your using an antena on your tv for this test, as cable Tv uses sheilded coaxial cable to dampen interference) you will get limited interfearence even though the tv is in a DRASTICLY different band as your TX. all radio signals merge together. however im liking the explanation of the close proximity to a strongle signal locking up the RX. sounds the most probable to me.

and whos to say that his tx wasnt slightly outa phase with the band he should be in and that brought it down. granted, its MUCH more likely that some one else ruend on the same frequency as you and started rangetesting the possibilioty there for catostrophic interferences in still possible. though very unliky.

what band was he on?

50%plane

My Feedback: (5)

Pfine, are you just going let us speculate on your mental capacity, the band you fly on or anything else that we might attempt to answer without the facts.

Where are you Pfine?