Paul Saccani wrote:
> On Thu, 18 Sep 2008 23:19:06 +1000, B J Foster
yahoo.com>
> wrote:
> >> Paul Saccani wrote:
>>> On Wed, 17 Sep 2008 23:08:33 +1000, B J Foster
yahoo.com>
>>> wrote:
>>>>>>> Paul Saccani wrote:
>>>>> On Tue, 16 Sep 2008 08:38:45 +1000, B J Foster
yahoo.com>
>>>>> wrote:
>>>>>>>>>>> Mobile phones use UHF frequencies and do *not* interfere with aircraft
>>>>>> navigation systems. The issue is that whilst the interference is
>>>>>> infinitesmally small it cannot be entirely dismissed - so the rule
>>>>>> remains. In practice it is ridiculous.
>>>>> I've actually seen mobile phones interfere with VOR, the needle
>>>>> swinging from side to side until they are turned off.
>>>> I find this very hard to believe.
>>> I knew that.
>>>
>>>> The VOR band is 108MHz to 118Mhz (VHF). The lowest mobile band (UHF) is
>>>> 900Mhz.
>>> So what is GSM400, GSM450 GSM 800 and GSM850 in that case?
>> Where are these GSM bands used?
>
> You tell me - after all, if you had given the matter any *real*
> thought you would know already.
>
>> AFAIK, we use 900 and 1800 in Oz
>
> We sure do - but phones that operate on the 400MHZ and 450MHz bands
> are sold and usable in Australia.
Oh for goodness sake, I'm not an encyclopaedia of spectrum allocations.
In any case, 400 MHz is still UHF and 282MHz distant from VOR but ATC is
the very next band.
>
>>> I'll give you a hint - the name is based on the band used.
>> Don't be rude
>
> Don't be precious.
If you have something to say, say it.
If you had a bad day, go take it out on somebody else.
>
>>> I think you don't know that you don't know.
>>>
>>> Then there is UMTS on the 700MHz band,
>>> CDMA 400, 450, 800 and 850 on their respective bands.
>> CDMA? What's that?
>
> You're the one attempting to make a technical argument - you should
> know.
I *am* making a technical argument and I *am* qualified to do so.
Your argument seems to consist trying to score points off the fact that
that there may be frequencies used somewhere between 118MHz and 900MHz
which is COMPLETELY IRRELEVANT to the fact that devices operate in bands
and ARE REQUIRED TO DO SO.
Yes, there *is* leakage, but extensive testing by Nasa and Boeing has
shown that it is minimal (path loss is around the 40-50dB mark).
In case you hadn't realised, CDMA is no longer used in Australia.
Please note the location of the ATC band.
>
>>>> If the VOR system has such a poor filter then it is going to be
>>>> affected by *every* *other* system between VOR and GSM.
>>>> For example:
>>>> 118–137 MHz: air traffic control
>>>> 137-138 MHz: meteorological satellites
>>>> 144–148 MHz: Amateur radio
>>>> 156–158 MHz: VHF Marine Radio
>>>> 175-216 MHz: television channels 7 - 13
>>>> 174–216 MHz: wireless microphones
>>>>
>>>> ...and so on...
>>> I can't recall using that equipment to transmit *in* the cockpit of a
>>> VOR equipped aircraft. Perhaps you fly in a different manner to
>>> me.....
>> ATC is the nearest & indeed the next band!
>
> I suggest you heed the emphasis. Transmit *in* the cockpit.
Ho hum.
One would presume that reputable aircraft equipment manufacturers manage
to minimise interference between VOR and ATC (located in adjacent bands)
devices *in* the cockpit and the antenna (located on the fuselage) and
if the filter has a high enough Q-factor to eliminate interference between:
VOR: 108-118Mhz
and
ATC: 118–137MHz
Then one would presume that 900MHz is *extremely* unlikely to cause
*any* inteference even on the passenger deck.
You sound like you know a few buzzwords just looking for an argument.
>
> Now, whilst I have occasionally used hand helds in the cockpit, I've
> never done so in a VOR equipped aircraft. It just isn't something
> that happens very often, because a VOR equipped aircraft is going to
> have a radio installation that transmits on the *outside*.
Like I said elsewhere in this thread, the approach taken by regulators
should be to *accredit* each phone-aircraft combination, phone by phone
and plane by plane.
>
> This is totally different from a mobile phone in the cockpit, which is
> where I have seen the VOR needle dancing around until the phone is
> turned off. Others have reported interference to com. radios.
Until the phone is *turned* *off*.
Do the same with a non-phone PDA, or a smartphone in "flight mode".
Betcha you see the same problem.
>
>>> I find your argument lacking.
>>>
>>> Common experience should already have alerted you to cell phone
>>> interference with *audio* amplifiers, let alone radio ones.
>> As I mentioned that is more likely to be due to the CPU.
>
> I know you said that, but I really am not convinced that you know what
> you are talking about.
If you follow advice from usenet, you probably shouldn't be flying. That
you considered it is already a concern.
Credibility on usenet depends on the argument made ... and the
recipient's capacity to understand it. So one of us has a problem - and
it's not me.
>
>> Do some research on GSM and the permissible power *outside* the band. It
>> is negligible.
>
> Who did the research? The guy who knows what frequencies are used, or
> the guy making absolutist statements that have been shown to be wrong?
We both know (at least I hope so) that band allocation is BY DEFINITION
there to exclude interference. We also both know that interference MUST
OCCUR because there is no such thing as a perfect filter. But what you
possibly fail to understand is that a carrier signal at 900MHz, or
400MHz for that matter is about as likely to interfere with VOR at
118MHz as an electron tunnelling to Mars.
I am not ruling out that interference comes from the PED but if you read
the start of this thread, you will see that I postulate that this
interference does *not* come wireless transmissions, either GSM at
900MHz/1800MHz or 802.11/Bluetooth at 2.4GHz, but rather the CPU
circuitry - which operates at baseband - and which is orders of
magnitude more likely to be the source.
Thus the instruction from pilots to put phones into "flight mode" is
nonsensical as it switches off all but the most likely source of
interference.
>
>>>> NASA and U Okalahoma tested GSM and CDMA extensively and concluded as
>>>> follows:
>>>> "None of the 4 CDMA and 4 GSM wireless handsets tested would
>>>> individually be likely to interfere with aircraft VOR, LOC, GLS,
>>>> or GPS navigation radios".
>>> I would have thought that was an impossibly small sample size to draw
>>> conclusions from, especially as there are eight bands used by GSM
>>> alone! And this study covered only one GSM band, E-GSM900.
>> Which (happily) happens to be the lowest band used in Oz.
>
> Sadly for your argument, it doesn't happen to be the lowest band in
> use by mobile phones sold in Australia.
Yeah, so what is?
>
> Nor does it in any way justify your rather absolutist claims that
>
> "Mobile phones use UHF frequencies and do *not* interfere with
> aircraft navigation systems." and "The lowest mobile band (UHF) is
> 900Mhz.".
You can bet that the Engineers at Boeing and Nasa used terms like "could
not" and "would not" and these were watered-down by the Corporate Legal
department to "could not be reproduced in laboratory conditions".
>
>> In any case
>> the lowest band you mentioned, 400 MHz (which doesn't exist in
>> Australia),
>
> Doesn't exist, eh? But the phones that use it do! That's the
> important bit that you missed.
Who's being precious?
>
>> is sufficiently distant from 118MHz that the probability of
>> interference is equivalent to...a blue moon...or a logical debate on usenet.
>
> I don't see you as having the technical competence to make that
> determination, judging from what you have been saying here.
ROTFL. What determination? What is the probability of a "blue moon"?
>
>>> But maybe you are happy to disregard reports of demonstrated
>>> interference in favour of hypothetical rejection capabilities.
>> Not really. I took note of the fact that Boeing assiduously investigated
>> *every* case and in *no* case could the claimed/suspected interference
>> be repeated under controlled lab conditions.
>
> Talk about hyperbole!
>
>> Gee.
>
> What arrant nonsense.
>
Did you read the Boeing results?
>
>>> Maybe you don't understand the limitations of the study - passenger
>>> use on *transport* category aeroplanes.
>> This thread started with some guy (a passenger) being arrested for
>> "endangering" an aircraft - presumably a transport, since it was
>> transporting the aforementioned passenger.
>
> And I responded to the absolutely nonsensical claims that you made
> with regard to mobile phones not interfering with aircraft navigation.
Firstly, I did not make absolutist claims. This is what I *actually* said:
"Mobile phones use UHF frequencies and do *not* interfere with aircraft
navigation systems. The issue is that whilst the interference is
infinitesmally small IT CANNOT BE ENTIRELY DISMISSED - so the rule
remains. In practice it is ridiculous".
and
"The VOR band is 108MHz to 118Mhz (VHF). The lowest mobile band (UHF) is
900Mhz"
(CAPS added to assist comprehension)
Secondly, I did *not* rule out interference:
"I have a feeling that the CPUs within the devices actually cause more
interference"
You said that intereference with VOR IN THE COCKPIT stopped when the
device was TURNED OFF.
Gee.
>
>>>> (the safety margin for GSM was calculated as 47dB)
>>> This has only limited relevance.
>> True (lol). 3dB would be relevant...
>>
>>>>
http://www.humanitarianinfo.org/sumatra/mediacentre/press/doc/article/Electromag...
>>>>
>>>> They also found that "Interestingly, repeatedly turning the handset
>>>> power on-and-off caused the most significant changes in the spurious
>>>> radiated spectrum".
>>>>
>>>> This seems to dovetail with my earlier speculation:
>>>> "I have a feeling that the CPUs within the devices actually cause more
>>>> interference"
>>> I think you don't understand how these gadgets work.
>> What do you mean by "these gadgets"?
>
> Mobile phones and radio navigation systems.
If you're going to accuse me of making absolutist statements (which I
did not) then you need to be specific yourself.
>
>> For a start, signals on a computer bus are effectively baseband. That
>> means that they spread frequencies all over the spectrum *up to* the
>> clock frequency and beyond.
>
> I take it you mean broad band. Baseband is an entirely different
> thing.
And you claim that "I don't see you as having the technical competence"?
Broadband is a meaningless term.
Baseband is baseband. It means that the low-end frequency is 0MHz and
that there is no upper end. I trust that you'll realise the significance
of this on the relative probabilities of sources of interference.
>
>> In contrast, GSM operates in a band and any noise/crossover is limited
>> to sub-bands within that band.
>
> In contrast to your rather limited understanding of the technology, a
Which technology? rotfl
> GSM phone transmits at maximum power across up to four bands at
> startup. Surprisingly, this maximises the interference that it
> generates.
X-rays and Gamma rays are invisible
>
> Compared to 2 Watts of several different modulation schemes generating
> heterodyne signals, the noise of the CPU is rather minimal.
You're digging yourself deeper
>
>
>>>>> Thus, "do *not*
>>>>> interfere with aircraft navigation systems" would seem to be somewhat
>>>>> of an overstatement. Interference with VOR has been reported quite a
>>>>> few times.
>>>> Do you have a reference?
>>> I told you that I've seen it myself.
>> EM radiation is invisible.
>
> Short attention span?
>
> " I've actually seen mobile phones interfere with VOR, the needle
> swinging from side to side until they are turned off. "
See above
For all I know, you had a fridge magnet attached to the underside of
your phone.
>
>>> Beyond that, its been in the
>>> crash comics.
>> Huh?
>
> Flight Safety Australia and the like.
>
> You know, the place where such problems might be reported on.
It means nothing to me. I looked for information from Boeing and Nasa.
Not Casa. Casa reminds me of Flying doctors and Dick Smith. I'm allergic
to peanut butter and I think that Aldi is great. Must be some reason for
calling them "crash comics" - wonder what it is.
