No doubt many will have seen the John Smyth’s email.
Yesterday one of our club members, Lee Hulme, was flying his Squall EDF jet when he temporarily lost control for a few seconds. Twice. Accompanied by David and George Rea they discussed the matter and concluded the following:
Lee has a top of the range JR 2.4 radio and was using a Spectrum long range rx. Our landlord, Dessie, has recently aquired a wifi setup (from Sunday) and Lee’s phone in his pocket was wifi enabed at the time. Upon disabling the wifi on the phone and leaving it in the car Lee flew again without incident. Maybe a coincidence?? Remember wifi is on 2.4 ghz!!
Please pass this on to anyone using 2.4ghz radio equipment.
So what can be the problem? Is it the 2.4GHz being used by the i-Phone that causes the problem or is it ‘something else’??
My initial answer to John was:
Hi John, I would be more inclined to blame the fact that he had the phone in his pocket, close to the tranny.
When the phone starts looking for someone to talk to it is likely to start tranmitting at full power ’till it gets an answer. (This is one of the reasons BMFA says: no phone near your tranny). The phone network does not use 2.4Ghz and the wifi would likely be out of hearing range, unless you are literally within 50-100 meters.
Any bit of electronics will get upset when you blast a strong RF signal into it’s innards.. That is is a top of the line JR is no help (or hinderance). Electronics is what it is. Per definition any bit of wire or any length (including any trace on the pcb’s) can/does act as a pickup for electrical signals. If you are unlucky enough to get enough rubbish in the CPU chips, they’ll reset themselves. Sounds to me that’s what happened.
And since it is the top of the line JR, it has all the fancy low power/high performance/extremely sensitive CPU’s that drive the innards..Try making a phonecall to someone with his phone in his pocket, and see what happens. 9 out of 10 times it might go right. Anyway, it would help is you give additional details:
- phone make etc.
- distance to the wifi network (clear line of sight?)
- what make wifi (there are dodgy ones out there, transmitting at more than the allowed 100 mWatt.)To give you an example: I have a modified Multiplex Cockpit, with a Spektrum module. The Cockpit is very sensitive to phone disturbance.
So, all I need to do with my rocksolid Spektrum link, is put my phone in my pocket on a nice and lonely slope, far away from civilisation, and when the phone starts to look for someone to talk to (every few minutes!) it will upset the Cockpit electronics enough to do a restart.. So, the fact that it’s a 2.4 link means zilch, The actual RF chip is unlikely the part that is affected, it’s the stuff before that. (JR uses the same RF modules as Spektrum, They are exactly the same for ALL modules, including the one in my Cockpit. I’ve done quite a lot of research into those modules. Because Spektrum/JR use off the
shelf modules, they do not need to pay the astronomical fees for certification. The only difference between the modules for different radio’s is the interface tot the tranny.http://www.unigen.com/product_detail.php?pid=729
http://download.cypress.com.edgesuite.net/design_resources/datasheets/contents/cywm6935paec_8.pdf
or: http://www.blokland.net/?p=266Anyway, the moral of the story is still: do NOT put your phone on your pocket!!
I asked John for some further clarification and this is what he said:
…the phone is an I-phone, distance (to the network point) probably about 100 m or less, and don’t know the make or details of the wifi but we can all use it from the pits area no probs! JS
To that I answered..
I would be very worried if I had an I-Phone in my pocket in that situation!
Just pray the wifi is always on, so that the Spektrum chips can look for a free channel. You are not in a good place!
It’s the one (_don’t mention it_) downside of the Spektrum system, it selects 2 channels on power up, and if something decides to start using those channels, you have a problem..
Don’t forget we do not have exclusive use of that band, EVERYBODY and his uncle is free to use it, as long as you stay at the 100 mW power level. And the channels are not as tightly specified either. They are sort of there, but not like on a 35 meg system.Futaba would deal with this easily, since it uses frequency hopping, as does my own ACT system..
As it is, be very wary of people using laptops and anything else to connect to the network when you are in the air.
I would really make it a rule that people do leave their phones in the car and NO laptops or other network stuff to be used when people fly.
Without further experimentation, it’s hard to be 100% sure, but I doubt it is the 2.4 link, since when Lee put his phone in he car, all was well.
However, just to be sure to be sure: leave your phone in the car!