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this page was first published there has been something
of a revolution in transmitter prices thanks to the
For a mere £20 or so you can buy a Boafeng transceiver which has CTCSS tones to activate the latest
repeaters. These radios also have a very easy interface
with external devices such as timers and audio sources,
via the jack on the side, there is also power available.
It is dead easy to
rig up a repeater jammer/bug/improvement device now, you
also have a power source for the timer available. For
our prototype, (which we think is the first device of
this nature with CTCSS), we used the lead from a
speaker/mike and the work took less than 20 minutes to
complete using a sound module from a greeting card as
the audio source directly wired to the mic input. 100%
Above is what you
get in the box, they even include the plug and lead, so
just cut off the remote PTT and earphone! It's all too
easy and too cheap these days, you lucky people! Just
search eBay for Baofeng, although the same radios are
available under other just as dubious, names.
A prototype "Project X" device has already been
made and it is extremely useful, a few modifications are needed before
our modular device can be deployed properly, but the performance of the
Mk1 is very encouraging.
Project X was a suggestion from an unlikely
source at our 2014 AGM, something none of us was aware existed was
handed over by a member, a GSM remote switch!
Basically, it is the main core of a cell phone
with a SIM card carrier and a relay, it is supplied with a free SIM card, just
put it in and switch it on. A call activates a relay and your remote
control switch turns on your device, you can even program it for time
intervals etc. a very useful gadget, again from eBay.
Use this in conjunction with the Boafeng, and
you have a self contained, small, easily deployed device that has lasted
at least 5 days in field tests. A doubling of the useful time
between charges can be as simple as adding a light sensor so the GSM is
only powered in either daylight or darkness. Again, as everything else
today, eBay has many ready made devices for sale.
Modular construction simplifies the job, please
DON'T try saving space by dismantling the Boafeng radio, just take our word
It is fair to say that several
similar projects can be made from old cell phones, but we got this GSM
controller donated, however a quick search of eBay UK shows similar
devices from £29.95, but be sure to get a 12v one as some are sold for
home automation and are mains powered.
Our prototype can be activated by
anyone with the SIM card number calling it, it doesn't answer, but the
relay activates upon a call. It also has the ability to respond to only
one calling number or up to 10.
If only such things were available
in the "good old days", what fun!
Sorry we can't make public the
size, shape, and colour of the finished article as it would make it too
easy to find, but the whole thing is marginally larger than the radio
and in a waterproof/rainproof housing.
Only a little more work is
required to refine the design, possibly with the addition of a separate
battery for the GSM controller as it has to be on all the time to work.
It was suggested at the AGM to
book into a hotel and install one in the room, but there is too much of
a paper trail to do that without being traced, but what an excellent
idea, rather like the "bug" an LPWS member left powered by his bathroom
light when he moved house, nearly 5 years passed before it stopped
working or was eventually located - and it was a mere 200 yards from The
Birmingham HQ of The Radio Investigation Service and the exact same
building OFCOM now use for their Spectrum Engineering Officers.
Below is a compilation of old pages, how things have changed!
Build a Repeater Bug/Repeater Jammer!
your own repeater bug, or repeater jammer, with our help and advice!
Find your target repeater with the Grid Reference
You can target
your own local repeater, or make a device with variable frequencies that you can
use on your travels, now that prices of hand held transceivers are falling, especially
second hand ones.
Not a great deal of practical knowledge of electronics is
required to construct a device, but you will need the basic skills of soldering
and drilling etc. Don't be too ambitious at first though, our advice is to keep it simple.
We have made 2 distinct types of device, the simple ones, such
as "Tony Toneburst", and the more advanced ones with music, messages, and digital
Equipment / Transmitters
Wood & Douglas
144FM2T3 transmitter board. As you can see, it is quite small, but compared with some of today's transmitter boards with
surface mounted components, it is huge!
This is the
Electronics FM6, it is TINY and ours transmits 30 miles and accesses a
repeater on a ¼ wave length of wire just as shown! The picture shows the top of
the board, the components are surface mounted beneath. Shown in this picture are
the battery (top), a standard crystal (centre) and a microphone (bottom left). A
good feature is that this transmitter works with a mere 6 Volts.
Here is another variation of the FM6, this one was produced by
in the States, but sadly they have gone out of business
leaving us with only 3 of these wonderful transmitters. As you can see, this one
is crystalled for 145.025MHz, and has given sterling service in the past. We had
to remove it from a device to take this picture.
This is the
smallest crystal controlled transmitter we have found, and by far the best. This one worked well in
tests, although its use has been limited to a radio rally "talk in"
frequency. Fitted inside a packet of 20 cigarettes with a laughing module and 4
AA batteries, it was carried around inside a radio rally by an unsuspecting
person while we monitored the effect from outside. It is rock solid on
frequency, and powerful for its size. For the test we used a loosely coiled ¼
wave wire inside the cigarette pack. It completely obliterated all signals due
to its close proximity. This picture shows it before the crystal was changed,
and the microphone replaced with a sound module.
To convert any of these type of crystal controlled transmitters for repeater bug use, the
crystal needs to be replaced. New crystals are available from :-
PO Box 19
Phone 01322 330830
Fax 01322 334904
To work out the frequency required, a little simple maths is required. Assuming you know the
frequency the unit is currently set to transmit on, (if you don't, a scanner will give an approximation) and divide INTO
this figure the currently fitted crystal frequency. This will give you the
MULTIPLIER, quite often 12.
For example, if the transmitter is set for 169MHz at present and
the crystal has 14.08333 stamped on it, then the multiplier is
12. (14.0833 X 12 = 168.9996, the Tx frequency)
For Example:- To convert it
to transmit on 145.025, the input frequency of a repeater on 145.625Mhz,
divide 145.025 by 12 to get the crystal frequency, order a crystal on 12.0854. It's that simple. To ensure the
correct type of crystal is supplied, we suggest unsoldering, and sending the old
one with the order, that's what we always do.
For some very good transmitter kits and other interesting things:-
Their FHT1 "foxhunt" transmitter, for
US$89.95 had definite
possibilities and it is microprocessor controlled with variable time delays etc.
It represented excellent value and should have done the job well with only minimal modifications.
Sadly no longer available from the manufacturers, although you may find one
if you search.
Download our simple resistor colour code
All these circuits use the versatile 555
Improvement Device needs to be triggered by a timer. There are
a few suggestions .
Our first really successful device, Tony Tone-burst
(named by the repeater users, not us), it consisted of
a battery, a transmitter, a 1750KHz tone burst board and 2 simple 555 timers.
Why 2 timers? You need 2 specific timing intervals,
one for the interval between transmissions, and one for the interval
transmission, later, greater experience gained from making these devices
reduced the component count considerably.
Tony Tone-burst sent out a 500 millisecond
burst of tone every 28 seconds, this would open the repeater, and just as it
was about to time-out, and it was sending it’s Morse ID, the device would
send another tone burst and reset the repeater’s time out timer.
This was made before we came across the circuit for our own
tone-burst that has a built-in duration timer, if a similar device
is made now, only the one timer is needed, the one to set the
tone-burst interval, as the duration of the tone is pre-set to
Actually, it did
nothing to jam or prevent use of the repeater, but as radio amateurs are not
fully paid up in the brain department, they would not use it or speak to
anyone! In fact several people genuinely believed it was manually operated and
that someone was actually sitting and pressing their tone-burst button every
35 seconds or so, and we were accused of paying someone to do it. As they
say, the pictures are better on radio!
Later modifications to Tony Tone-burst were a
small “laughing module” from a greeting card, and an increase in the
transmit time to 1 second. This gave the following effect, tone bust >
repeater opens > brief trademark laugh > silence………..timeout
repeater Morse ID > tone burst again > and so on.
For a more standard device we have found
that a transmit period of no more than 30 seconds provided the required amount of
annoyance without transmitting long enough to be tracked down.
A maximum of 3 transmissions per hour will
keep them guessing as to the location, but we suggest only 2 per hour. A
simple way to achieve this is to use a small quartz clock mechanism, these are
only a few pounds and there are many ways to trigger the transmit timer with
A really simple way to trigger the device is
to find the works from a chiming quartz clock, these have two wires coming
from them that are attached to a pair of contacts that "make" once
per hour, throw away the hands and use these wires to trigger the transmit timer.
Don't be too over
enthusiastic with transmit periods and the number of transmissions, many of our
newer constructors have suffered the loss of expensive equipment this way as
the "sensible" radio hams will DF the unit and steal it given half a
A really good ruse is to construct two
identical devices and have them set to trigger alternately from different
locations, prolonged use of this example showed that they just confused anyone
trying to locate them.
The following two simple timers can be constructed without a pcb if required, just
solder the components onto the chip, this saves space in a confined area.
Both designs are tried and tested and based on the common 555 timer chip,
where power consumption is a factor, substitute the standard 555 timer
with the µ555 version, but take care as these are very delicate with
regard to static electricity.
hope the circuits are self explanatory! All resistors are ¼ Watt, take
care with polarity, the "idiot" diode can be omitted if you want.
This timer is the standard
design used by us for over many years, the original is
working! It provides the power for your device via the normally open
contacts of a sub miniature relay, test have shown that reed switches,
although drawing less current, are not nearly so reliable in service. The
input "pulse" wanted is a momentary make contact, this starts the timer
cycle. Various things can be used for this, but bear in mind that some
devices, although they work well in test conditions, do not function when
in the close proximity of a transmitter.
Our most successful devices have
used one or more chiming quartz clock mechanisms. These are available for
a few Pounds, and have a pair of wires that make momentary contact once
per hour. Throw the hands away and just use the bare mechanism or 2 for
twice an hour operation. Crude we admit, but in the field they work better
and more reliably than other designs of more technical merit!
VR1 should be around 1MΩ - 2MΩ to give an on time of around 20 - 30
seconds only, this may not seem a lot, but take our advice, any longer and
they will almost be able to DF the unit and steal it! You may need to
experiment with the value to get your required "on" time.
This is from the very first successful
device made by the LPWS, and nicknamed "Tony Tone Burst". This device
utilised the repeater's characteristics to keep it open as the close-down
Morse ID was being given. On the face of it, nothing much really, but
radio amateurs being what they are, find this monumentally annoying, this
stops them from using it as effectively as a 100 Watt carrier, take our
word for it. This timer needs to be coupled to a transmitter with a
automatic tone burst and the timer pulse adjusted to coincide with the
repeater's closedown, usually around 30 seconds of non activity. The tone
burst then resets the repeater timer and the cycle repeats. We know it
sounds too simple to be effective, but remember we are dealing with simple
souls, IT REALLY DOES WORK!
The blue resistor is the
timing period controller and the one to change to suit your target repeater, ours
has a hard wired resistor, but obviously a variable resistor can be
Diode D1 in both circuits, as well as the
"idiot" diode are standard diodes you find lying around, if you want a
part number, try using 1N914, 1N4148, or similar
Theoretically, the 555 can supply the
current for a low power device without a relay, but remember we are
dealing with RF in close proximity, and in practice this does not work as
the timer needs to be insulated from RF feedback. Consequently, a relay
must be used.
The idiot diode is there merely to
prevent damage from reverse polarity, not a bad idea if you are making a
sealed package, it will protect your circuit during use and testing and
any accidental reverse polarity when changing the battery pack.
Testing can be done easily with a simple
led and resistor such as this:-
suggest the complete and tested circuit is fitted with wire "tails" for
connection and sealed with self amalgamating rubber tape, or silicone
sealant, to prevent
the ingress of moisture etc.
Here is a
block diagram of the component parts of a Repeater Bug, for ease of
construction we always power the sound source and clock timer separately
from 1.5 volt cells soldered in place, in practice these batteries last in excess of
From the relay in the timer module, one
"hot" wire is required to power both the tone burst and the transmitter,
if a more complex audio source is used, extend the wire to activate this
In the old days we had to use an auto-reverse Walkman unit with a
C60 cassette in it, until the tape broke! Luckily, now we have innumerable sources
of digital sound recorders and audio modules available for a few pounds,
like the birthday card laughing module that is ideal.
1750 KHz Toneburst
Due to the introduction of CTCSS sub
audible tones, the following information is somewhat obsolete, it will
remain here for historical accuracy. To open the vast majority of repeaters
in the UK, you now need a continuous tone on your transmitted audio, that is
supposed to be below the range of human hearing.
Full details of CTCSS tones along with
ways of modifying existing equipment can be found on our
CTCSS TONES Page
To access most repeaters in the UK, a 500
millisecond 1750 KHz tone burst is required. When the repeater hears the
tone, it switches on the transmitter and re-broadcasts anything heard on the
input frequency. Most repeaters using CTCSS still retain the ability to be
activated by the old style tone.
There are numerous
commercially made tone burst modules available for the modification of ex PMR
The Wood & Douglas TB2 tone module, shown here, can be easily
made yourself with readily available components.
The adjustments are for output level, set at quite a low volume
for best results, and the of the tone burst frequency. One advantage of this
module is that it actually times the length of the burst to 500mS itself. This
means that it can be wired across the input and when power is applied, it self times the tone burst,
If you are a clever sod, like some of us, you can make your
own tone-burst module with the LPWS design below.
This is a simple, cheap, and effective 1750KHz toneburst circuit, essential
for "opening" older repeaters in the UK.
This circuit has the added advantage that it can be left powered as it has
an inbuilt 500 mS tone-burst timer. [i.e. when power is applied, the tone-burst
only sounds for 500mS, after than a mere few µAmps are needed on standby]. If you are using a common ground (0V) you may be able
to use just the output to the "hot" side of the TX input, check for
polarity, otherwise it can be wired permanently across the input in parallel
with your audio source.
The IC is a Motorola MCI 4001BCP or
The only important adjustment is RV1, this controls the output frequency.
There are several ways to adjust this, but assuming you don't have a frequency
counter, you can use trial and error by testing it on your target repeater.
Start with the trimmer in the centre position, most repeaters are very
tolerant! [unlike the repeater groups!]
Another tried and tested way to set up
the tone is by ear. Use a hand-held or a known good radio, and monitor it on a
scanner, with your tone-burst connected to your transmitter apply the power and
adjust for the same tone. RV2 adjusts the output level, in general, we have
found the lower the level - the better it works.
If you want to get a constant output from the LPWS tone-burst circuit for
testing etc. simply apply 12 volts via a 100K resistor to pin 6. This will
disable the internal timer.
This can be built on a board, or to save space, we have one actually built
entirely on the back of the MCI
4001BCP chip. Another space saving way, is to use an IC
socket, solder the components to the pins before plugging the chip in. After
testing, both RV1 & RV2 can be substituted for fixed resistors to save
Tried, tested & it works!
(well ours do anyway)
a website for the hobbyists, like the majority of
LPWS members, there are interesting projects and loads
of modifications for existing kits. OK, not all radio
related, but some interesting things just the same. Look
in the TECHNOLOGY section.
Instructables, we have just made one of
these TV-B-Gone devices a mere US$19.95 kit.
Great fun when
such places as Comet and Currys, also in department stores, be
careful in pubs though if there are any
morons watching football! Plunges John Lewis
and Selfridges into silence!
A good 25
metre range, sometimes up to 50 metres. The
small EPROM contains a list of "off" codes
for nearly all brands of TV, pressing the
button starts it scrolling through the list
with Samsung, Panasonic, Sony & LG coming at
the beginning. Another press starts the
sequence again, the whole list takes about a
minute to finish.
(A side effect
of this device is that it will turn on any
set that is already off though.)
range IR diodes and 2 wide dispersal diodes,
can be modified to take a matrix of 24!
A good source of circuits for
hobbyists can be found