tracking down interference was Re: [TowerTalk] electric fence qrn

[Jim Lux]

Probably, more accurately, it would be the responsibility of the "operator" 
of the interfering device (i.e. the entity that has control over whether it 
is on or off).  Who owns the source of the interference  (or who 
owns/controls the physical location of the device) is probably sort of 
irrelevant, except as they control what the operator does.

If you had a noisy neon beer sign in your bar, leased/loaned from the beer 
company, the FCC would make you turn the sign off, not the beer 
company.  You might then be able to go and harass the beer company into 
giving you a new sign.

But this does bring up a sort of interesting question...

If the device is type accepted or were required to have a Part 15 placard, 
though, it might be a be a bit different. Consider the TV antenna amplifier 
that oscillates... the operator is responsible for shutting it down if it 
interferes, but the manufacturer might be on the hook for something if the 
device doesn't meet the certification requirements it was approved under.

What about the cable TV line amp that oscillates? It's almost certainly a 
type accepted piece of equipment.  Who's responsible? The mfr of the 
oscillating amp? The cable company that uses the facility? The independent 
entity that owns the physical plant and leases it to the cable company? Yet 
another entity that actually is responsible for maintaining the physical 
plant under contract to the local cable company?  Is there a difference if 
the amp were installed incorrectly (maybe it's not stable into all loads?)

What about RF devices that are intentional emitters, but which have no 
placards? I assume you go deal with the operator of the device, but that 
can get a bit sticky.  Say I'm doing 10 GHz moonbounce or a I have a 10 GHz 
data link to an amateur buddy, and the local gendarmes put one of their 
X-band radar trailers outside my house, interfering with my receiver. The 
radar trailer is operating perfectly, it's just an unlicensed, in band 
emitter, subject to Part 15 (just like 2.4 GHz ISM stuff in the middle of 
the 2GHz ham band).

I figure I would go to the operator of the interfering device (i.e. the 
police) and tell them to cease operating their device.  This presumes that 
they're even aware that it is a Part 15 device (it is, a special section 
covers this in Part 15) and that they know they have to shut down if they 
are interfering. Interestingly, these trailers do NOT have a Part 15 
placard on them (which is probably violating Part 15, since they ARE an 
intentional RF emitter), at least the three I've looked at in the last 
month (two owned by the PD, one by a private security company).

Presumably, there's some radio tech at the PD who might know about this 
stuff (probably because the radio tech is a ham), but, the Explorer cadet 
who pulled the trailer and set it up?  You'd probably have to spend a fair 
amount of time on the phone until you got ahold of someone who actually 
knew what you were talking about.

I wonder what the (practical) responsibilities of a "potentially 
interfering device" are in helping to determine whether their device is 
actually causing the problem; maybe it's not the 10GHz radar trailer 
transmitter, but my ham neighbor, who's a hermit and incommunicado, who has 
decided to put up his own 10GHz link, unbeknownst to me.  In any case, 
though, what's the standard of proof required to ask someone to turn off 
their interfering signal?  An order from the FCC based on their van coming 
out and making measurements?

This will become a bigger and bigger problem as wireless stuff becomes more 
common.  BPL is only the beginning... Already, the 2.4 GHz ISM band is 
quite cluttered, and tracking down interference is a real challenge, since 
the transmitters aren't 100% duty cycle.

I'd feel a bit uncomfortable going up to my neighbor and telling them that 
their brand new wireless LAN is interfering with me, and they need to shut 
it down.  This is a lot different from the classic "noisy light dimmer" or 
"broken fence charger" kind of thing, where the RFI is indicative of some 
failure of the consumer equipment, because their equipment is working 
perfectly, within spec.

Jim, W6RMK

At 07:39 PM 12/9/2003 -0500, Cqtestk4xs at aol.com wrote:
>In a message dated 12/9/03 1:40:13 PM Greenwich Standard Time,
>kg5u at hal-pc.org writes:
>It's not the
>responsibility of the noise source's owner.
>According to the FCC, it is the owner's responsibility...at least that is
>what the FCC and the ARRL told me.
>
>Bill  K4XS
>_______________________________________________
>
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