[d@DCC] Signal interference in Bill C-2: Any engineers want to explain this?

[mskala at ansuz.sooke.bc.ca]

On Sat, 14 Feb 2004, Russell McOrmond wrote:
[quoting debate]
>     What is worse, the cards that fool satellite receivers also emit radio 
> signals that may interfere with military emergency radio equipment. Not 

[Russell:]
>   This seems bogus to me, but not being someone who has investigated this 
> specific technology I do not know for certain.  If there are people with 
> the right credentials to talk to parliament then they should do so.  

The problem is that like so many other things, it's impossible to make an
absolute statement because the FUD is so vague.  Is it true that illegal
receivers "may" emit radio waves?  Sure!  Is it likely to cause any
problems?  No.  Any receiver except a crystal radio, basically, will
contain an oscillator of some sort, and all oscillators emits a signal on
some level that you could pick up with a suitable sensitive receiver.  
That's how "radar detector detectors" work - they tune into the "local
oscillator" in the radar detector.  It's also how the BBC's notorious
television detection vans work.

The emissions from a receiver are generally very weak.  You have to try
pretty hard to pick them up.  If you tried really hard, maybe you could
design an emergency communications system that could be interfered with by
a satellite receiver.  Is that likely to happen in practice?  Not at all -
any emergency communications system that could be affected by that would
have to worry a lot more about sunspots, rain, people looking at it funny,
and so on.  (Sunspots and rain are *real* issues for emergency
communications systems depending on the frequencies in use, and they
totally dwarf "interferance from satellite TV reception equipment".)  

Also, the satellite receiver people have obvious reasons to want to limit
the detectable emissions of their equipment, and it is not necessarily the
case that a high-emission receiver would be any easier or cheaper to build
than a low-emission receiver, so even if you believe "Oh, pirates do
shoddy work!" (not necessarily true) it doesn't follow that "pirate"
equipment will be any more interferance-causing than "legit" equipment.  

Another issue is that illegal satellite TV receivers are generally just
legal satellite TV receivers with the dish pointed at a different
satellite and a different decryption key loaded.  So the vast majority of
illegal DirecTV setups aren't emitting anything that isn't also being
emitted by the legal ExpressVu setups next door.  It's identical
hardware.

But is it *possible* that an illegal receiver could screw up some piece of
military hardware, somewhere, some time?  Well, sure, anything's
*possible*.

My own qualifications on such things boil down to having an Amateur Radio
license with Advanced qualification - which ought to be enough, but we can
probably find someone with more impressive credentials to say it.  (Having
that license, BTW, makes my home fall onto the list of places the Radio
Inspectors can enter *for sure*...)
-- 
Matthew Skala
mskala at ansuz.sooke.bc.ca                    Embrace and defend.
http://ansuz.sooke.bc.ca/

--
For (un)subscription information, posting guidelines and
links to other related sites please see http://www.digital-copyright.ca