"aemeijers" wrote in message
news:bcWAj.732298$kj1.552302@bgtnsc04-

snip

Don't know about the current case, but the ones previously written up
were NOT LMR systems, trunked APCO p25 or otherwise- they were radar r&d
sites.


the new system at Eglin AFB ran afoul of some locals in the
developments nearby (who discovered their garage door openers
were being hit with the equivalent of a jammer - the emitter
being the control channel of the new trunking system).

there have been other reports of similar spectrum issues at
other installations.

now in a different reverse case, the military is claiming
amateur radio repeaters are interfering with some PAVE PAWS
radar sites. which the ARRL is cooperating with them to
address the issues.



One of my duties at work is buying LMR systems, so I do
understand how those work. (or in the case of the local public safety
LMR, NOT work.)

is "MA/COM" in that scenario ?


I've never heard of a trunking control channel causing
problems for garage door openers- the repeaters just aren't that
powerful.

typical output on a licensed transmitter is approximately 55 watts
out of the transmit combiner to, say a 100' high, 7 db gain antenna. so
anyone can do the math here. a nominal receiver sensitivity number
for receiver 5% BER (on the subscriber side) is probably about -120 dbm
of signal.

the "average" part 15 consumer device is hard of hearing to begin
with (compared to a $4000 high end Motorola unit). so it has some
attenuation hearing it's intended signal (the remote) to begin
with. flooding the area with the control channel signal only adds
to the noise mask the garage door receiver would need to struggle
against.

also keep in mind, these systems operate in the spectrum slots
assigned to US federal govt users. so, it's not going to be the
800 mhz, or 450-512 band slices.

the remote manufacturers rolled the dice (on operating on frequencies
that could be reclaimed by the govt at anytime), and they lost.
unfortunately the consumer is caught in the middle. of course,
the manufacturers specifically have wording in their manuals that
address the possibility of interference and disclaim all liability
for same.


I suppose it is possible, but reorienting the antenna for the
part 15 device usually would fix that.


see above, maybe, maybe not - probably not.



No, a base commander is not gonna break his budget or compromise mission
capability to keep the locals happy. But since 'having a good working
relationship with local civil authorities' is one of the things he gets
rated on, he isn't gonna tell them to eff off, either. Having a senior
tech and a PR flack give a few tours, and provide info to local media,
can go a long way.

agreed, most CO's are politically savvy (unfortunately so in some cases,
but we won't go there).


aem sends...