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2.4 GHz dead zones


TonyS
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A couple of weeks ago when I was flying my Parkzone Mustang at the club I noticed that the motor cut in and out. Ever nervous since my recent awful experience with 35Mhz I asked if anyone else had noticed.
I was surprised when a couple of the very regular 2.4 GhZ flyers told me, in a very matter of fact way , that "it always happens over there - you're best keeping out of that area, it's a dead zone".
The club is right out in the country - no houses, aerial masts, pylons or other nasties etc (Maybe the odd electric fence but I was over 100ft up so....) .
Recently I was flying my funjet in the fields by the farm and I lost all connection with the plane which subsequently had to be retrieved from 40 ft up a tree!
 
Surely, a radio signal will go everywhere and be of equal strength for any set distance (particularly if it's in line of sight)
How can there be "dead zones"? 
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Posted by Stephen Grigg on 05/06/2010 21:18:32:
I did feel I had  problems with my first 2.4 set up.,and twice in the same place when I lost 1 model to a tree,and retieved the other after a month.I changed to a Futaba set up and its been fine since

 What were you using before? 

I have never had that problem. I use futaba. What do you use? I was under the impression that you couldn't get interference, only signal blocking... 
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I've never experienced that with my Futaba 2.4 gear. So far 100% "reception". Which can be a problem as any "funny" movements by the model are all mine - no excuses!
 
BEB
 
PS Please believe this is not an "opening salvo" in a Futaba vs Specktrum debate - in my opinion they're both great systems! I post it simply as information toward the discussion.
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In the last two weeks, three models have been lost at our club. All were using AR 500 receivers, and all were flying over the same area. All the pilots (including my son, who lost his Wot 4 yesterday), were experienced, and all suffered a total loss of control.
As we fly on MoD land, it was assumed that the military might be using comms equipment in the area which was blanketing the signals, but it seems to be more general.
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what about antenna orientation - donut of death - if everyone in the club has the antenna the same way - possible - and is stood in the same place the DoD will always be in the same area....

Edited By Olly P on 06/06/2010 11:49:55

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Speaking s an OLD telecoms tech with no Ghz knowledge.
It was easy for a very stong signal on a totally different frequency to swamp the front end of a receiver making it deaf.
This could fit your dead zone problem if a long haul high power microwave beam is passing though your site.
 
I could be wrong, but it sort of fits the scenario.
Mike
..
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I had a fantastic deal with Galaxy when they exchanged my 2.4 system,and I had a lot of unexplained incidents ,some losing models that appeared to have gone out of control.As Ive no proof of equipement failure,Im not prepared to name the manufacturer.Suffice to say there response was second to none with all of my problems but when I lost my Pulse,enough was enough.Im pleased to say Ive had no problems since changing
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  • 1 month later...
  after a couple of years of trouble free flying, iv noticed a few clitches and then crashes (not mine YET!) while fliers were on 2.4ghz.. Ive also noticed that they have occurred when a Police car has been parked in the area and when an AA van has been assisting a fellow club member with his dead car.
  Is it my imagination or is there a patten starting to build out there.  
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Over the weekend I've been playing with the FrSky telemetry set, which gives feedback if the signal becomes weak.   On friday I could get repeatable weak signals warnings in two spots on our field, if the models were flying in a left hand turn at a set distance and modest height (150 - 200'?), perhaps this was a combination of rx aerial orientation and background noise?  Neither model was affected badly enough to trigger the failsafe, nor even to show a glitch in the flightpaths.  Initialy I put it down to the rx aerial placement, but on sunday I didn't get a single peep in the exact same spots with the same models.
What does that tell me? Only that the more feedback you get, the more you worry.
It did highlight how much the signal strength varies with both rx and tx aerial orientation though.
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Hi all, i lost my Super Air a couple of weeks ago, i thought the engine had gone sick ( been fine for years) so it went dead stick and tip stalled in, not major damage just enough to want a re-cover.
After stripping the engine, no fault found, tank, no fault found i put it in my speed air  ( on 35megs) fine no problem.
 
Makes me wonder if it went into failsafe for some reason.
 
Really not sure about 2.4.
 
Regards
Chris
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My flying field is well away from houses etc, so can I rule that out?
On one particular day we had 3 (so called) unexplained losses, all within 45 mins, it was then we noticed the police car parked up on a lane that runs at the edge of the field.
Now...is it not the case that emergency services work on 2.4 and at very high transmitting level????
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Posted by KELL on 28/07/2010 19:26:47:

Now...is it not the case that emergency services work on 2.4 and at very high transmitting level????
 
Not as far as I'm aware they don't.  Many (most/all?) UK police forces use the TETRA network run by O2.  This is digital and encrypted and operates on 380 to 400 MHz.  The older analogue radios previously used operated on lower frequencies - remember how you used to be able to hear police radio above 100MHz on a standard FM radio?  That was "a few" years ago though,  before the FM broadcast band was used between 100 and 108MHz!
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Ok thanx John, I guess we can rule out any interference from the emergency services then. It looks like it might be just plain old pilot error "blamed" on the mystery interference by rather embarassed fliers. Come on chaps own up if you cock up, then we can all learn from eachothers mistakes, and keep our hobby a safe one.
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I believe that there are 2.4Ghz line of sight (dish to dish) telecoms links out there, often used because no licence is required. These could cause a "corridor" of doom cutting across the corner of a flying field.
 
Another possibility is blanking of the signal by an engine, motor, battery etc. Has your problem been at one particular model attitude, that puts the receiver on the far side of a metal item in your airframe?
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What Chris writes here is important as a 2.4GHz signal behaves rather like a lightbeam. So if there is some kind of conductive material between your transmitter and your receiver this could be screening the receiver from the signal. Think about carbon parts, aluminium tubes and so on. Sometimes a slightly different receiver position can be the solution.   
 
And: never point with the antenna to the model. 90 degree position gives you the maximum transmittion.
 
Last point: who says that your transmitter or receiver ar error free. I have a DX7 which killed 3 models until the Horizon service repaired it (for free - which doesn´t help my models...) with the comment that the transmitter output power was too low.
 
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Hi all, i think that as soon as they can sort out the line of sight on 2.4 and make it as good as 35 megs is? then it will be fine.
 
I wonder how many people have lost aircraft on 2.4 as opposed to 35 ?
 
For me, and i have two Futaba 2.4 sets, i will revert back to 35 megs for any " special or expensive " aeroplanes until we all know just how good the 2.4 gig stuff really is.
 
I love the fact that we can turn up and switch on, brilliant, but we need the reliability of 35 with the freedom of 2.4
 
Just my thoughts
 
regards as always
 
Chris.C
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