Mythbusters Episode and FMS

wrote:

On Feb 10, 10:19 pm, **THE-RFI-EMI-GUY**
wrote:


Its just plain good sense not to use cellphones in an aircraft. Has
anyone noticed how a NEXTEL phone will tear up speaker phones and
computer monitors? Its the pulsing of the time division multiplex (TDMA)
RF signal that gets inadvertently coupled into electronics and biases
transistors on and off. Think what would happen if a passenger left that
phone turned on in a bag near a bulkhead next to some sensitive avionics
box and a call came in. Whenever I read about A/C having "uncommanded"
control movement, I have to wonder about that environment.





snip

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P- Hide quoted text -

- Show quoted text -



Not gonna happen. Avionics have to survive HIRF RF at 100V/M over the
entire RF spectrum.

The real threat is to radio receivers for navigations and
communications. A cell phone can swamp out the receiver and block
important signals. They cannot cause any permanent damage such as you
are describing because of the shielding and other design practices
that are put into place to handle HIRF...

Dean Wilkinson
B.S.E.E. and avionics designer



Do the levels of the HIRF specs pertain to permanent damage or do they
pertain to "upsets"? I wasn't talking about permanent effects. What I
have seen is that these phones very easily cause upsets to consumer
grade equipment. Granted one would expect avionics to be well sheilded.
I would hope that extends to sensors as well.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P

On Feb 12, 8:51 pm, **THE-RFI-EMI-GUY** wrote:
wrote:
On Feb 10, 10:19 pm, **THE-RFI-EMI-GUY**
wrote:

Its just plain good sense not to use cellphones in an aircraft. Has
anyone noticed how a NEXTEL phone will tear up speaker phones and
computer monitors? Its the pulsing of the time division multiplex (TDMA)
RF signal that gets inadvertently coupled into electronics and biases
transistors on and off. Think what would happen if a passenger left that
phone turned on in a bag near a bulkhead next to some sensitive avionics
box and a call came in. Whenever I read about A/C having "uncommanded"
control movement, I have to wonder about that environment.

snip

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P- Hide quoted text -

- Show quoted text -

Not gonna happen. Avionics have to survive HIRF RF at 100V/M over the
entire RF spectrum.

The real threat is to radio receivers for navigations and
communications. A cell phone can swamp out the receiver and block
important signals. They cannot cause any permanent damage such as you
are describing because of the shielding and other design practices
that are put into place to handle HIRF...

Dean Wilkinson
B.S.E.E. and avionics designer

Do the levels of the HIRF specs pertain to permanent damage or do they
pertain to "upsets"? I wasn't talking about permanent effects. What I
have seen is that these phones very easily cause upsets to consumer
grade equipment. Granted one would expect avionics to be well sheilded.
I would hope that extends to sensors as well.

--
Joe Leikhim K4SAT
"The RFI-EMI-GUY"©

"Treason doth never prosper: what's the reason?
For if it prosper, none dare call it treason."

"Follow The Money" ;-P- Hide quoted text -

- Show quoted text -


Avionics aren't supposed to be upset or damaged by HIRF. For some
categories, test levels can be as high as 200V/M

Consumer grade equipment isn't designed to these standards because
they don't need to be, and they can't be due to cost constraints.
Avionics designs are low volume high cost products...

I have designed for both Laser Printers and avionics, and they have
very different design requirements.

Dean