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What Is A REPEATER?
What is a repeater, well we all know but it
is obvious that many people are unaware of what a repeater is and
what it does.
Basically, it is a receiver and transmitter
usually mounted at an elevated position, to enable communication
over a greater area than simply station to station.
ALL repeaters in the UK are privately owned
and funded and are freely available for anyone to use, despite what
so of the "repeater groups" think. What happens is a group get
together and buy or build the required equipment, find a suitable
place to mount it, and get the necessary permission from the
property owners, plus get a power supply to run it.
A repeater is an automatic device that when
it receives a signal on one frequency, will automatically
re-transmit it on another. In the past, repeaters were activated by
sending a 1750KHz tone, some still respond to this, but nowadays it
is more common to use
CTCSS tones that seamlessly
activate the repeater when you wish to use it.
As most 2 Metre and 70 Cm radios are fairly
limited in range, repeaters are found at almost 30 - 40 mile
intervals. So called "Short Wave Listeners" monitor repeaters as do
the majority of active radio amateurs, standard practice is to call
for a contact on the repeater, then go and find a free frequency,
although there is no reason not to continue on the repeater if it
takes your fancy.
As you can imagine, repeaters are where the
fun is and have long been abused with all manner of devices and just
simple mucking about and playing music. On the repeater you have the
biggest audience, so naturally that is the place to play.
Repeater abuse has been tackled many
different ways over the past 50 years, all with little effect,
changes in legislation now mean that the "Repeater Keeper" (the
licensee of the station) is responsible for anything his station
re-transmits, and many people have installed remote switch off
facilities. It can be endless fun forcing the keeper to switch it
off, waiting for it to come back to life again, then forcing it off.
You have to remember that these people have
constructed, paid for and installed this equipment for the sole
purpose of retransmitting what is on one frequency, on another,
usually at much greater power and over a vastly wider area, and now
they are also responsible for that signal. In the past, people have
been prosecuted for repeater abuse, and the evidence given has been
nothing but the retransmitted signal - the change in the legislation
means that whatever the repeater retransmits is the direct
responsibility of the repeater keeper, and any so-called abuse must
be traced back to the source rather than just using the repeater
output as evidence.
R.I.D. Repeater Improvement
An alternative source of transmitters can be
found now that the prices of NEW handhelds have significantly dropped.
currently some bargains about, and new ones can be bought for as little as
£50.00. Consequently, this has affected the second-hand market, a few years ago
bought 2 small second-hand Icom DJ100s for £30.00 each, so this may be a better
route to a quality transmitter with a tone-burst already fitted.
Here is an
Alinco DJ100E bought off Ebay for just over £20, it is compact, powerful and
robust with a tone-burst and variable output power, a bargain. Now a very
stable and versatile repeater jammer can be made for well under £100.
radios are ideal, high power output, low current consumption, plus you can
change the frequency without the hassle we used to have in finding crystals.
They are small enough to fit inside small die cast boxes, and if left in
their case, RF proof insofar as the transmitted power does not seem to
infiltrate the audio source. You can knock up a really good device for well
under £100, deploy it, and retrieve when the battery is flat minimising the
chances of being caught to almost zero! Search eBay to find some bargains.
If you discard the battery
section, the whole unit is
then really quite small. We usually use Yuasa 12 volt jelly cells from B&Q
burglar alarms, although for
solar powered applications NiMh batteries are superb.
For 2 Mtrs., a ¼ wave wire antenna needs to be approximately 48.5 Cm long
or 19.2 Inches in English! You can coil it or extend it, although as most 2
Mtr repeaters are vertically polarized, best results are obtained from a
vertical wire. Experiments have been carried out with long wires, and even a
very successful test using a barbed wire fence! This was excellent as the
signal appeared to radiate from a large area, although when it rained, and as
the barbed wire fence wasn't insulated, it stopped working almost all
Keep it simple at
first, an ideal audio source can be found in musical or speaking greeting cards.
As you can see, they are small, cheap, and their audio output is just the right level
to be connected to the microphone input or either of the featured transmitter
boards or a hand held. Throw away the silly button cell, and power it from an AA
battery or from part of the device's power source. No more than 1.5 Volts
We favour the Yuasa 12 Volt jelly cells used as standby power on
burglar alarms, these are relatively cheap, but do not try recharging them with
a car battery charger! NiMh batteries are also very good, NiCads are a bit pathetic really as they suffer from
the dreaded "memory effect".
construction of the bug
A decent R.F. proof housing needs to be used for a device made from a
transmitter board, there are some ideal die cast casings in the
In our original designs, all the components, including the battery, were in
the same casing. This was sealed against rain with silicone sealant, with an
insulated connector for recharging the battery. This worked quite well until
the small amount of gas given off from the lead acid jelly cell whilst
charging, started to corrode the tracks on the circuit board!
We now favour the transmitter, audio source, and timers being sealed inside
their own waterproof die cast metal casing, with the battery attached to power
leads. The Yuasa batteries are quite capable of being exposed to
the atmosphere with no detrimental effects, and this design has distinct
advantages, we just put a couple of rubber bands round the 2 items.
No possibility of corrosion due to acid fumes,
and the batteries are easily changed.
In the past, a well sited device needed to be collected, taken home and
re-charged, then replaced in its hiding place. With a separate battery you do
not run the risk of being found with the device in your possession either at
home, or to and from the site. Thus a possible source of problem is completely
removed as you can simply change over the battery as and when it needs
replacing. A 15 to 20 second blast every 30 mins usually gives at least 8 days
use. It is unwise to regularly change batteries, for example, every
Sunday afternoon. It is best to be as random as possible, and even leave
a discharged unit for over a week before recovery.
A 1.9 A Hr battery will give at least a full week of 24 Hr. use at our recommended
intervals, that is no more than 2, 30 second bursts in any hour. As we have
already said, our extensive tests have shown that this gives the required
amount of annoyance coupled with a great degree of difficulty for DFers!
For devices made with old hand helds, a plastic case is usually good
enough, as the radio has enough R.F. screening in its own case.
One of our most
successful campaigns used 3 identical devices, all timed by quartz
chiming clock modules, set to go off at 20 minute intervals. The 3
devices were 15 miles or more apart across 2 counties, but still
each one was in line of sight to the target repeater, it still bring
a smile to my face now, remembering the monitored conversations of
the people who spent night after night trying to locate what they
thought was just one device.
15-20 seconds an hour might not sound much, but getting a blast of
Laughing Policeman Song 3 times an hour really sent some of the
straight laced buffoons right to the edge, and whilst they spent
every night racing round the countryside in 2 or more cars, we
stayed at home in the warmth listening to their fruitless search
tactics, very satisfying. 100% success! Now fully documented
locations can be quite interesting. Devices can be placed either in
built up areas or in the countryside, ideally, within line of sight of a repeater. They need to be
camouflaged to a certain extent to avoid being found accidentally.
We recommend the use of a handheld to test
the sites selected. Set your radio for the LOWEST output, we suggest a few
milli-Watts, if you can still open the repeater, then the device will as well!
This aspect of the hobby can be
more informative, rewarding, and educating than many of the more legitimate
pursuits of the cardigan wearing loonies!
There are no end of possibilities for the
ingenious here. Some very sophisticated devices have been made with digital
speech modules, a vast improvement over the original auto-reverse walkman we
used in our Mk.3 model!
Technical progress has brought the price of
these modules down to just a few pounds, and they have the advantage of non-volatile
memories, so they retain the message or music even when the power is removed.
One of our members, who travels the country on
business, has a very nice gadget that plugs into the mike socket of the Yaesu
radio in his car. It plays small snippets of songs and abuse at random intervals
from a neat sound module, and draws its power from the mike socket. Limitations
of this aspect of our hobby will only be brought about through your lack of
Phantom Repeater Fault Module
An interesting and
simple device was made by an LPWS member that transmitted only a very
low-power carrier wave on the repeater input frequency, no sound and no
tone-burst. When someone used the repeater, all seemed OK until they
stopped talking, the repeater was held "open" by the lower power bug, it
then timed out if the other party didn't talk over it.
You have to think
about it, as it is not readily obvious what this 'easy to make' device can
do, if you are on the repeater committee it looks like a serious fault
that has to be rectified, to the casual listener it's not obvious.
However, this has the effect of targeting the very group of hard-core
nutters that matter, the demented repeater keeper and his cronies, it'll
have them pulling their hair out - if they have any left.
The power was so low
that it was impossible to locate, with the repeater's TX signal firing up
every few minutes. It was powered by 4 AA rechargeable cells, which gave
it a little over a full day's use. The repeater group still have no idea
about this device, their reaction was to assume the logic was at fault
and constantly take the repeater apart!
The device was
recovered every few days, recharged, then replaced. The repeater group
then assumed the logic circuitry at fault again, and they spent ages
trying to locate the fault. Dead simple, highly effective, and cheap,
and they are still none the wiser!
Here is a picture of
the actual device
Made from a virtually scrap device
bought at a rally for £5.00, subsequent variations have been made just
10% of this size, using the much smaller crystal controlled bugs, the
only factor controlling the size being the power source.
commercially available crystal controlled transmitter modules.
All you need
is 48.5Cms of thin wire for an antenna, and off you go.
At this low power, antenna matching is
not a problem, in a rural situation you can actually use a length of
barbed wire fence, for example, as a long wire antenna. A prototype we
tested was constructed in a small black plastic box with just a wire and
crocodile clip protruding, this was attached to the fence wire and
provided a carrier strong enough to hold the repeater input open, over 2
Total cost, under £50, entertainment
value £ PRICELESS!
2011 - Components for a RID
(Repeater Improvement Device)
A quick look around the Internet
has brought up good sources of parts to make your own Repeater Bug.
You can't beat a second-hand
handheld as the transmitter, reliable, re-tuneable, usually with a
tone-burst included and small. Check Ebay.
Digital Recording Module, sound
source, just the job and very cheap
Quartz Clock Movements:-
We can't find any identical
quartz movements at the moment, the ones the LPWS used were
standard quartz clock movements with a pair of contacts that
momentarily made contact "on the hour" and triggered an external
This is one of the chiming
quartz clock movements, the 2 wires "make" momentarily every
hour to provide the trigger for the timer. OK not high tech, but
experience shows that electronic timers don't like being in
close proximity (inside the same box!) to local RF sources.
Advantages:- It works, the
battery lasts >6 months, cheap, accurate - so you know when in
the hour the device will be triggered, small.
Audio Source/Digital Sound Module 2012
Many thanks to G6JNS for
emailing this marvellous device! It works, it's cheap, and it's
With 20 seconds recording time
it is the ideal sound source for a Repeater Improvement Device,
20 seconds might not sound much, but it is just about perfect.
The output is OK to use straight across the microphone input of
most handheld transceivers or you can retain the speaker for
The microphone for recording your sounds or message is on the
right, the other 2 components are the push to record button, and
the push to play button. The latter would be replaced with a
trigger from the timer or a simple tiny relay will do.
Designed to run on 6 volts, but seems to work quite well below
The best thing about this is the
price, £3.59 inc VAT!!