Re: Ultralight DX on an Airplane?


Phillips
 

Pilots can request retransmissions to ensure understanding.  Besides, pilots are uncanny in their ability to understand voice communications over aircraft radio circuits despite all sorts of interference and distractions.


I spent years working avionics and there is very little that could be affected by a local oscillator.   All I can think of is maybe an AM direction finder.  Aircraft still use LW beacons for airport-status but any receiver tuned to air-ground-air comms would be so far up the spectrum that its local oscillator would be orders of magnitude away from the LW frequency.   As local oscillators are set to frequencies above received frequencies, it is highly unlikely that even a LW local oscillator could get down to a LW beacon.  


Mobile (cell) phones can transmit up to five watts even when not actually making a call.  As would tablets and other SIM-card-equipped  devices.  And they transmit that high power using digital encoding.  I am sure that the 20+Kms of wiring in a modern commercial aircraft would ingest a lot of that power.  How many people turn their phones completely off when in an aircraft?   I'd worry a lot more about digital 5W phones inside a digital aircraft than analogue microwatt superhets.


There are WiFi equipped devices which transmit digital signals in the 2.4GHz or 5.8GHz bands.  They produce only small amounts of power but it is deliberately radiated.   How much of that power is picked up by the aircraft?


Then there are external sources of interference.  Two fly-by-wire Airbus aircraft in the same area over the Indian Ocean to the North West of Australia, have suffered sudden loss of control followed by equally sudden restoration of control.  Someone using their phone......or transmissions from the super-high-power HAARP installation on the West Australian coastline almost directly under the flight path?    Maybe something else.    Fortunately no one suffered serious injury and there have been no recurrences since the two incidents.  Perhaps someone changed procedures or maybe the aircraft have been "hardened".


Eventually it all boils down to how well aircraft are engineered to be impervious to extraneous electronic insult and they are very well engineered indeed.  I don't fly myself (no need to) but I let my wife fly without any qualms, even on the "HAARP route".
 
Ray



From: ultralightdx@... on behalf of Michael michael.setaazul@... [ultralightdx]
Sent: Tuesday, 18 September 2018 3:55 PM
To: ultralightdx@...
Subject: Re: [ultralightdx] Re: Ultralight DX on an Airplane?
 
My understanding was that the original concern was that an oscillator
emitting inside the cabin *might* disrupt pre-digital avionics
- not crew communications. With advances in electronics, this has
been superseded by other concerns.

Michael UK
.............................

On 18.09.18 01:52, ray Phillips phillicom@... [ultralightdx] wrote:
....
> Superhet radio receivers are those that have a local oscillator and can
> emit a radio signal.
....
> The local oscillator signal is small and does not contain any modulation
> and so will not carry any sounds from inside the aircraft.  At worst it
> will generate a fixed tone in the pilots' headsets.
....
> When flying in commercial aircraft, you can be assured that the aircraft
> is totally secure from locally generated interference.
> Ray


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