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ADVANCED SIGNAL ACQUISITION FOR PRIV

Found at: 0x1bi.net:70/textfiles/file?hamradio/nigelspy.ham



      ADVANCED SIGNAL ACQUISITION FOR PRIVATE SCANNER OPERATORS

         By Nigel Ballard 28 Maxwell Road Winton Bournemouth
            Dorset BH9 1DL ENGLAND.  20 July 1990

There is more than one way to skin a cat. So if we put our brains into
top gear, let's consider some alternative ways to hunt down those
llusive spot frequencies.

The first and most obvious way is to let the scanner do the work by
area up into small segments, then concentrate on that one single area
for say two days, mathematically your chances of coming across active channels
are greatly increased. Repeating this process across the band over a
this right? So on we go with some different approaches.

THE PLAN OF ATTACK!
Firstly, get hold of a trade magazine that covers PMR business radio.
Make up a good sounding company name and tick all the boxes relating to
antenna's and two way radio's. The company name is to ensure they bother
n replying. When all the info arrives you will have the start of your
dentification file. The more companies you get info from, the greater
the chance that if you spot a radio or antenna, you will be able to
through and inwardly digest the look of various antenna designs, even
though different companies make them, a low band folded dipole pretty
much looks the same who ever you buy it from. Excepting a few strange
variants you cannot change the laws of physics, a uhf yagi is a uhf yagi
and they all look pretty much identical. Catalogues covering handheld
from the antenna is long and thin on the UHF, but long and fat on the
VHF there is no real physical distance. So if you spot someone
nteresting walking around with a h/held, you try and identify the make,
match that to the antenna, and already you have narrowed down the

Gathering similar information on two way radio's, although useful is not
quite as productive. However some producers have different front panels
for different bands. Also if you peer in a car and spot a tone pad or a
operating frequency, as monitoring a possible allocation and never
channel. Remember that CTCSS tones used to open repeaters etc are below
the usual range of the human ear, so you won't hear them. DTMF however
s familiar to everyone. And five tone signalling is equally easy to

MOBILE ANTENNA'S
After a while experience will immediately tell you that the antenna on
the car in front is a quarter wave on high vhf, a centre loaded collinear
on uhf, or the familiar cellular antenna etc etc.  About two years ago a
friend introduced me to a man who wanted to pay me some serious amount
of cash to locate the frequency of a competitor. After a moments thought
challenge. So off I drive to the competitors head office, luckily enough
they had a two way radio on the roof, unluckily it was one of those
bitch to identify because low gain, high gain, low band and frequencies
up to 950MHz are all catered for in these tubes of various lengths. Using
a frequency counter was out because the roof was too far away from any
arrive. Ten minutes later a car pulled into their yard with an unloaded
the UK the limits for PMR users in this area are BASE TX 164.5 to
line of work, so I discounted these. I then entered in every gap or
all. One by one I heard traffic that didn't fit the bill, until much
later in the day the scanner stopped on a conversation that looked
buggers. Case closed and another gold star for this frequency detective.

COVERT ANTENNA'S
There are certain people out there who for one reason or another who would
not want it known that they are radio equipped, and as such they go
covert. The radio is either well under the dash, mounted in the glove
box or remoted from the trunk. But they still need an antenna. Over the
years I have seen allsorts of approaches from antennas mounted in the
tuned printed circuit board stuck on the roof and covered with a smooth
layer of body filler or a vinyl roof was layed over the top. The latter
s still very much in use, the only way to tell is to spot two identical
cars parked side by side, the one with the covert antenna will have a roof
about 4mm higher than the other car, or a non standard cloth top. But
antenna. Basically what you have is an exact replacement for the factory
to both the car and two way radio. Filtering in the diplexer stops the
RF shunting up the car radio lead.  They work better than any other type
currently available, the signal is vertically polarised and most of the
Some types however are actually thicker than the standard unit, so get
those micrometers out boys and girls. The only other spanner in the
car antenna into the rear window defroster wires by way of a large
choke. This causes problems to the covert unit. I know of one such car,
a Ford Granada that has the so-called covert antenna mounted on the rear
external antenna's. I have heard that some people are experimenting with
using the rear demist wires as the transmitting antenna, but so far the

GETTING BOLDER
find an older and more layed back officer, approach him with a look of
admiration, say hello and remark, 'your handheld looks heavy don't you
mind lugging it around all day?' with this the macho officer will yank
t off his/her belt and hand it over so you can be suitably impressed.
My first course of action is to flip it over and see if any of the
channels are etched on the back. Some crystal controlled radio's come
using this innocent approach. Having a good memory helps greatly. This
method works for both public services and private companies. Those
and you might get lucky.

RADIO RALLIES
to amateur radio dealers who sell them on as seen, many work and many of
the older one's still have the crystals installed. Once again I have

Well that's about it for now. Once again I hope I have given you a few
emitter density, radio location methods and the little known I.F.
Best Regards Nigel.