On Thu, 18 Mar 2004 16:09:58 GMT, krackula wrote:

NP ....... I had a friend that owned an auto parts yard. he had 8
channels of professional , high powered, wireless 2.4 gig installed.
he had it for only about 4 months and a lady down the road , a
quarter of a mile, got a new ( $79 ) digital cordless phone for
christmas and completely ruined the system

Then the system was not professionally designed and installed.

Very VERY few are. There's a lot more to this stuff than buying black
boxes from a spy shop or dealer and hooking them up.

There isn't enough space in the 2.4 ISM band to support 8 channels of
video. 5 is the maximum, even with gain antennas to isolate. If there
were 8 channels, they were spaced too closely, the receiver AFCs were
fighting to decide between several channels and the effective
sensitivity of the receiver would be reduced significantly.

I will acknowledge you can get more separation by going to circularly
polarized antennas instead of linear, and making each adjacent
frequency the opposite polarization, but you're talking a lot more
engineering than nearly anyone would be capable of. Anyone putting in
a system in an auto parts yard is not going to be doing military grade
work and spending a few hundred dollars each for sixteen antennas.

The ready availability of wireless stuff has made every wannabee into
a video and surveillance expert. If you don't believe they're an
expert, ask them. They all think they are. The appropriate test
equipment alone costs more than most of these companies will earn in a
year.

I train government law enforcement and see what it takes to bring
competent experienced professionals up to speed on wireless video.
It's nearly impossible to find a website or catalog with honest specs.
250 milliwatts at 2.4 is insanely high power and virtually never
needed. All the work in wireless video is done in the antennas, not
with raw insane transmit power.

I've personally examined several alleged high power transmitters and
not one was anywhere near rated spec. Jumping out the attenuator pads
in the Wavecoms more often reduces ERP than increases it, because
people screw up the impedance jumpering. You have to jumper with
copper strap, not wire, and maintain the precise inductance as the SMD
resistors you're replacing, or you lose signal instead of gaining it.
Very easy to see on a spectrum analyzer.

local teenagers started playing hide
and seek games in his lots ( full of cars ) using those
hand held video monitors ( like the icom ic-r3 ) and paintball
guns. he could never catch them, because they always knew
when he was coming

Another indication the system was not professionally installed, if
true.

I owned an R3. Others have brought theirs over here too.

My home and shop are next door to each other, on adjacent properties.
I test between buildings. I keep a Part 15 2.4 gig video transmitter
running constantly with color bars modulating at the house, as a test
source for receiver work at the shop. Antenna is a rubber duck about
the size of a cigarette.

Proper equipment with simple rubber duck antennas makes it fine
between the buildings, which are wood frame and only a few hundred
feet apart. No foil backed insulation, just paper.

The R3 would not see the same transmitter through one adjacent wall in
the next room, maybe fifteen feet airline. The professional receiver
sees full quieting even in the pouring rain when you need a
significant fade margin.

Anyone expecting the R3 to receive wireless video is likely to be
disappointed.

Steve


************************************************** *******************
Steve Uhrig, SWS Security, Maryland (USA)
Mfrs of electronic surveillance equip
website http://www.swssec.com
tel +1+410-879-4035, fax +1+410-836-1190
"In God we trust, all others we monitor"
************************************************** *******************