💾 Archived View for spam.works › mirrors › textfiles › hamradio › morehint.ham captured on 2023-06-14 at 17:02:07.
-=-=-=-=-=-=-
MOREHINT.TXT
Written by Nigel Ballard
28 Maxwell Road
Winton, Bournemouth
Dorset BH9 1DL
England
November 1990
Well I missed out some hints and tips from the last article, so here
goes with MORE hints and scanning tips you never knew you needed!
MAKING USE OF THE CAR STEREO
As already mentioned in my first article, but certainly worth bringing
to your attention once more. TANDY/RADIO SHACK and a whole host of other
electrical retailers sell a cheap adaptor that allows you to connect
your portable CD player through the car stereo by way of a dummy
cassette tape. Basically, you insert the dummy tape into your player,
the trailing lead plugs into your portable CD player, and hey presto you
now have the audio boost that a good radio car stereo can give you. Also
two or even four properly mounted car speakers is certainly going to be
better than the teeny weenie one in most portable scanners. And yes, your
scanner works great through these adapters. Although you may need to
bridge over the left and right channel wires, or fit a mono jack unless
you only want your scanner coming out of one channel in the car.
THE DARK SIDE
It appears that many of you liked the fact that I have in the past
discussed what might be called THE DARKER SIDE of radio. I must confess
myself to having a soft spot for anything covert. After all if THEY don't
want us to know about something, then surely it must be worth knowing
about! Am I right or what?
Anyway to continue our travels through the darker side of radio, here's
probably the most you have ever seen written about covert bodyworn radio
installs.
MORE ON COVERT KIT
I have already told you how the pro's mount covert radio kit in their
cars, but I never told you how the FOOTMAN or covert operative goes
about communicating without attracting attention. There are many
variants, and I will now outline the most popular.
THE HARNESS
This is the central piece of kit for the covert footman. What you have
is a skin coloured nylon or leather harness that fits around your
shoulders and has at least one pouch that hangs under the armpit. As
most people are right handed, therefore an armed undercover person would
want to reach for a side-arm on his/her left side. Thus most covert
harnesses are slung under the right hand side. So in the rare case when
a suited operative actually has his/her suit buttoned up, look out for a
bulge where the radio is slung. I know of many services where covert
radio users have their suits made to measure, they turn up for a fitting
already kitted up with handgun and radio harness, and the tailor makes
the measurements around the extra hardware. Double breasted suits are
not favoured for two reasons, a. the normal style of a double breasted
suit is rather tight around the midriff, and b. there are usually too many
buttons required to correctly button up a DB suit, more importantly
there are two many buttons required to undo such a suit in a hurry. If such an
operative on close protection work noticed the finely machined barrel of
a snipers rifle protruding from a window in the general direction of
his PRINCIPAL, the last thing he needs to do is fumble about with a
whole stack of fiddly buttons to gain access to his side-arm. Another
fashion point worth mentioning is that DB suits worn open look very
scruffy, and also leave a fairly large amount of cloth flapping around,
which might also get in the way should weapons need to be drawn.
A CASE IN POINT
Very recently, I saw some news footage of Margaret Thatcher leaving a
Sunday church service, it was a very windy day, and as the close
protection man came down the stairs he was wearing an OPEN double
breasted suit, clearly he had his left elbow held firm against his ribs
thus stopping his side-arm getting a preview with the awaiting press
cameramen. Trouble is the wind caught the other side of his jacket, the
right hand side flew open revealing the covert radio and harness.
WHAT GOES IN THE HARNESS?
THE RADIO
Of course there is a radio, it's horses for courses, ranging from single
channel clear mode to multi channel DVP or CRYPTO secure modes. I won't
dwell on the radio's in use other than to say the more important the
PRINCIPAL under protection, the more secure the mode SHOULD be. Not
always the case though.
Also as the RF output is never higher than five watts, typically three.
And as the human body quite happily absorbs a hefty chunk of the signal.
Therefore, the transmissions do not travel very far. On occasions a
mobile repeater is set up on a nearby roof-top to enable greater range,
and an ALL INFORMED NET. This though is only usual if the mode is
secure, as now the signal can travel some distance.
SECURE
The need for secure speech is paramount in the short term, and is only
slightly less important after the principal had departed. The short
term need is because the moves of both the principal and his/her
watchers and protectors could be gauged, and weak links in the
protection blanket could be made use of by any would be terrorist. The
problem with the secure traffic being decoded after the event, is that
pertinent operational tactics could be analysed and once again weak
points could be exploited in the future. This is especially true of
close protection, mainly because these people are trained to a fairly
set pattern, which in itself is a rather risky approach.
RECEIVING THE INCOMING TRAFFIC (THE THREE METHODS)
1/EARPHONE
2/EARMIKE
3/INDUCTION
1/ EARPHONE
Not much needs to be said about this method other than wired earphones
can get snagged, and are a dead giveaway to everybody else.
2/ EARMIKE
This method is a bit more popular, but still has all the downfalls of
the basic earphone. The only difference with the earmike is that through
the patented method of bone transmission, the tiny vibrations caused by
speech, and even whispers are picked up by the earmike and transmitted
down to the radio. Obviously full duplex comms is out because you cannot
get an earmike to receive and transmit at the same time. They do however
work very well, and even very quietly spoken words are picked up well.
This system is a natural for hands free VOX operated communications.
If you are still a bit confused by this principle, very simply it looks
like a standard earphone but also acts as a conductive microphone. This
method is well favoured by the US Secret Service.
3/ INDUCTION
For my money the best method. What you have is a flat induction coil set
into your cloth harness. Stuck in your ear is the smallest earpiece you
will ever see. Imagine a hearing aid so small that 90% of it is tucked
round the bend, with only a very small part visible. They are moulded to
fit snugly into the ear, and skin coloured so that a member of the
public would have to be stood very close and at your side to see you had
something stuck in your ear. They cost plenty, and have no volume or
on/off controls. You simply open a little flap, insert a tiny hearing
aid battery and off it goes. They only have a few down sides that I have
ever come across. 1/ they hiss all the time, even if the matching radio
is turned off 2/ people have been known to forget they had one inserted
and try to insert a second one, thus standing a good chance of
puncturing the ear-drum 3/ long time users have suffered high frequency
deafness as a result of extended use 4/ they have been known to
interfere with cinema induction sound systems (not very covert) 5/
because they are so small and rather expensive, if you loose one then
you spend the next week filling out forms and explaining yourself. I
have seen variants that use a clip that fits round the back of the ear
and attaches to the induction earpiece by way of a short length of fine
fishing line. So in essence you have a totally wireless earphone.
COVERT SPEAK
If your harness uses the induction method, the incoming traffic as taken
care of, but what about the outgoing speech? There are two methods.
Method one is a small electret microphone Wired directly to the h/held's mike
socket. You can either have it stitched into the very top of your
harness, or on the end of a long lead that runs down your arm. Covert
operators using the first method always seem to cock their heads over to
the mike side like an inquisitive parrot when speaking. Method two means
you have to bring your hand up to your mouth when you want to speak. The
microphone out of interest is usually held in place under the wrist by
either a velcro strap or a clip that attaches to your wrist watch.
THROAT-MIKE
This is a spin-off from the military use of a transducer style microphone
that is slung around the larynx (lower throat area) as you talk it picks
up your speech and sends it to the radio. The down sides are 1/ if you
have a large adams apple then they are bloody uncomfortable 2/ the
speech quality is really crap, very muddy with lots of base response and
no treble. It is very easy to determine covert users employing throat
mikes by their muffled speech. Like the ear-mike, throat mikes are well
liked by tactical firearms and SWAT units who need both hands free
especially if they are handling firearms. They don't need to be so much
covert as hands free. The ear-mike is by far the best solution as the
hurried radio command to 'FIND' something or other can easily be
interpreted as 'FIRE' if the adrenalin pumping person who issued the
order is wearing a throat mike.
SO THEN HOW DO YOU KEY UP YOUR COVERT RADIO?
1/microswitch
2/vox
3/pressure pad
4/switchplate
1/MICROSWITCH
usually down the same arm as your microphone you have a small press to
make switch in a little tube. Often they are attached to the same
velcro strap. When you want to transmit you bring your hand up to your
mouth, curl back a finger, push in the microswitch and speak into the
mic.
2/VOX
This is pretty obvious really, you might well have either an internal or
external vox circuit with an adjustable gain control. Over a certain
threshold, when you start to speak, the radio switches to transmit. Not
very good in noisy environments. Possibly the biggest downfall of the vox
principal concerns armed officers. If an armed officer gets involved in
a firing incident, the vox will trip on each firing and deafen all
others on the frequency.
3/PRESSURE PAD
Just like those alarm mats you might have just inside your front door,
when the house alarm is activated, if anyone steps on the mat, the
air spaced contacts meet and the alarm is tripped. The same principle is
employed for the covert operative. Usually they have a pressure strip
strapped onto the elbow, when the arm is raised up past a certain point,
then pressure switch is compressed in the elbow joint and the radio
starts to transmit. I have found this to be the least used approach.
4/SWITCHPLATE
This method is greatly favoured by firemen or anyone wearing heavy flame
or NBC (Nuclear Chemical Biological) protective clothing. What you have
is a switch that hooks onto your belt, it usually has an oversized
pressel, thus making it easy to key-up a radio even if you have heavy
gloves or mits on. This also works with covert radio users who can mount
the switch on their belts underneath suit jackets.
If you have thoroughly read and understood the last section, then I feel
sure you now know as much, if not more on the subject than the people who
actually use this type of kit!
A LITTLE MORE ON COVERT CAR INSTALLATIONS
As briefly mentioned in a previous article. I heard that certain
OFFICIAL bodies were both experimenting and actually using the car's
heated rear window element as a covert transmitting antenna. I have yet
to find any written information on how to go about making such a
modification. But within the last week a friend who owns one of the new
Ford Granada's had his heated rear window go tits up. Tracing the wires
back from the window, he found a diecast box marked FORD mounted on the
inside tail-gate behind the trim. He opened it up and found it to contain
several open coils and a number of capacitors etc. This has to be the
blocking circuit that stops the 12 volts from the demist circuit from
shooting back up to the radio. Remembering that a car radio is receive
only, therefore the problem with transmitting up the wire as well as
receiving must be quite a problem to overcome. Anyway I do think this
area is worth some further experimentation.
1. Would a scanner work well through one of these boxes?
2. Could one of these FORD boxes be converted for scanner use?
3. Is it worth rummaging around the breakers yard looking for one of
these boxes in a written off Ford and attempting to suss out how it
works? Yes I think is the answer to question three anyway. I even
believe there is a commercial market for any bright spark who
understands chokes coils etc, and can produce a product JUST for covert
scanner users. After all, the Ford box had no more than a few pennies
worth of components in it.
BASE ANTENNAS FOR SCANNING (reception only)
Alright, so this is a subject hammered to death by everyone else, but
as I feel sure that certain facts revealed in my articles will appear in
the scanning press, therefore I thought it high time to say my piece.
THE 16 ELEMENT DISCONE
Everybody's favourite choice?
Well maybe so, but it is only that by default. If you are lucky enough
to have a scanner that covers 25 to 1,000 MHz without any major gaps
then in all honesty, no one single omnidirectional antenna could do real
justice to such a wide area of spectrum.
HOW SO?
Well basically, if you have a quarter wave cut to a specific frequency,
then it resonates perfectly at that given freq. It has no gain, but not
surprisingly no loss either. Now as we all accept that any and all coax
has a loss factor, therefore by the time your feed from this imaginary
quarter wave reaches the antenna socket, you WILL have a loss. So then
your unity gain antenna will now be in a minus gain situation. All of
you in agreement so far? OK forget pre-amps for the time being, we are
talking antenna theory at present.
Right, now if I swapped by quarter wave for a GAIN antenna such as a
collinear, I might get 5DB gain over the quarter wave, allowing for cable
loss I would still be in a plus gain situation by the time we got to the
scanner. Still with the flow here?
So take a discone, forgetting the top loaded element many now have, they
all have one thing in common.....ZERO GAIN, in fact it is true to say
that in certain areas the discone works less well than a resonant QW.
So why does everybody buy them, and many pronounce them as the dogs
whatsits? It's back to the matter of default. You can only afford one
antenna, or maybe your landlord/parents will only allow one antenna, or
maybe you think you only need one antenna? Either way the discone is a
BIG compromise. And do not let smooth talking radio shop salesman tell
you anything else.
If you could only have one antenna, but you wanted a GOOD antenna, and
gain, and the chance do to some very loose direction finding what would
be your choice?
THE LOG PERIODIC
Most logs are sold to be used in the horizontal plane, whereas we want
ours in the vertical plane, any problems with that? Only one, if you
mount your log using a metal pole then the front lobe and ALL the logs
inherent characteristics are going to get screwed up. Instead of a good
front lobe pointing in the direction of the beam, you will instead have
a pair of rabbits ears protruding either side of the beams direction.
Also the gain will be affected. So rule one, use a non metal mounting
pole like fibreglass. Although the log is directional, you still get a
damn good signal off the sides of the beam. If you buy one of the
smaller Japanese variants such as the CREATE CLP-5130, then you will have
gain from 50 to a 1,000 MHz and not a pre-amp in sight. Add to your log,
a good rotator and some meaty 100% screen coax and you have a scanning
antenna set-up to be proud of. And as long as you didn't have a pre-amp
in line, you could even transmit through it. Yes, the log is a big boys
toy, but if you run something like the ICOM R7000 then don't you want to
get the MAX? I have seen the grove scanner beam, it roughly copies a
true log periodic, but there the similarity ends. I personally prefer
the CREATE log, and for the money you get one hell of a lot of metal in
the box, and the build quality is superb.
I'm bored already with talking about antenna's, so now onto something
else.