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All these circuits use the versatile 555
Any 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.
These 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 10 years, the original is till
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 or 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.