46 Silicon chip Australia’s electronics magazine siliconchip.com.au
then after a delay, retransmitted, to be
received by the receiver.
This effectively increases the range
for the transmission as it can be placed
closer to both the transmitter and re-
ceiver than they are to each other, and
possibly in a more advantageous loca-
tion (eg, higher up) where there will
be fewer obstacles in the way of both
signal paths.
Other types of repeaters exist, which
operate slightly differently to this one.
For example, many repeaters retrans-
mit the received signal on a different
frequency.
That prevents conflicts between the
transmitter and receiver and allows the
repeater to operate with effectively no
delay. But the final receiver must be
able to receive on the new frequency,
so that type of repeater is not ‘trans-
parent’.
This repeater retransmits in the same
frequency band as the received signal.
That means that the final receiver does
not need to be modified in any way.
But the repeater has to wait for the
end of the transmission before resend-
ing. Otherwise, the received and trans-
mitted signals will interfere, and the
receiver could even go into a loop, con-
tinually retransmitting the same data.Compatible projects
Some of the projects we have previ-
ously published that can benefit from
using this repeater:- the UHF Remote Switch (January
2009; siliconchip.com.au/Article/
1284 ), - the Versatile 10-Channel Re-
mote Control Receiver (June 2013;
siliconchip.com.au/Article/3811), - the aforementioned Driveway Moni-
tor and Infrared to 433MHz UHF
Transceiver (June 2013; siliconchip.
com.au/Article/3812).
All the projects mentioned above
used the standard 433MHz UHF trans-
mitters and receivers sold by Jaycar and
Altronics (as shown above).
The Jaycar catalog codes are ZW3100
for the transmitter and ZW3102 for the
receiver, while the Altronics catalog
codes are Z6900 for the transmitter
and Z6905 for the receiver.
This repeater may be able to be used
with some other commercial devic-
Screen2: the yellow trace at the top shows the original signal
being received from the source, while the cyan trace at the
bottom shows the signal being transmitted by the repeater.
You can see how it does not start transmission until it has
finished receiving an entire packet, and there is a short
delay before retransmission, around 60ms in this case.Screen1: the yellow trace at the top is the output from the
UHF receiver, RX1. You can see the high-frequency noise
before valid data is received. When there is a received
signal, the random signal ceases and the transmitted code
is produced instead. IC1 rejects the noise and only accepts
the valid code, as shown in the cyan trace below.
es transmitting data in the 433MHz
band, however, whether it will work
depends on the details of those trans-
missions, so it’s hard to say that a par-
ticular device will or will not work
until you try it.
Keep in mind that you need to use
the repeater in situations where it
doesn’t matter if the receiver could re-
ceive two identical packets in a short
period.
That’s because it may pick up both
the direct transmission and the repeat-
ed transmission in some cases.
In all the projects mentioned above,
this should not matter, as the receivers
are effectively ‘stateless’.
That should be true of many other
devices such as weather stations. But
again, you will need to try it out to
confirm that the receiver’s operation
is not adversely affected by receiving
multiple identical packets.Presentation
Our repeater is housed in an IP65
sealed box and that means it is suita-
ble for use outdoors, in areas where it
could be exposed to the weather.The 433MHz Data Repeater is based on commercial transmitter and receiver modules, as shown here. The Jaycar
ZW3100 transmitter and ZW3102 receiver are shown on the left with the Altronics Z6900 transmitter and Z6905 receiver
at right. They are for all intents and purposes identical; either will fit directly into our PCB.