rf transceiver

Hi all,

I am trying to build some transceivers on my own (-to build some door
lockers, rf switches), but to understand the basics I started to do
some reverse engineering on a powerhouse x-10 transceiver module.
These things seemed to be very basic to me. I tried to measure the
oscillator frequency by using a scope, and found out there is a 38kHz
oscillation in the circuit(it is not like a sinus wave, but sthg like
a binary signal 0 for half of the cycle, then it fastly oscillates
from -1 to 1 for half the cycle-scope does not trigger this part, it
seems like some relaxation oscillations in this part of the cycle).
Anyways the interesting thing is; there is a small copper wire-0.5cm
long, shaped as a half circle after the inductance in the circuit. I
thought this might be sthg like an antenna in this device, but my
antenna class reminded me that antenna lengths are usually on the
orders of the wavelength. But this antenna is very short (0.5cm is
60Ghz), is there sthg wrong with my knowledge, how does this small
antenna work? If this is an antenna how can I get an idea about the
radiation pattern, easily.

Thanks,
Adam

 

Hi,

Hi,

When you say a transceiver, are you referring to an RF transceiver?

The X10 Powerhouse kind of devices are not transceivers in that sense;
they take (receive) RF signals, and transmit X10 signals thru' the
mains line, not RF.

So, the small RF circuit you saw is just an RF receiver. The small
copper loop is like a coil in the circuit; the main antenna is the
external one that is coupled to the PCB thru' the plastic casing.

The circuit for this module is available at
http://www.geocities.com/ido_bartana/

In my experience, it is fairly easy to build an RF transmitter, but
the receiver is more complex; its better to buy the receivers,
although there again there are circuits available on the internet.

Regards,

Anand Dhuru

 

Thanks for the link. What I have is a powerhouse x-10 transceiver
module and a remote control chain kc674. The circuit that I was
describing is in the remote control key chain, so that circuit should
be an rf transmitter. If that copper circle is not an antenna, what
does a coil do in an rf transmitter?

Here is the link for the device I have;

http://store.yahoo.com/asihome/rcx10remkeyc.html

Adam

 

Hi,

I thought you were referring to the TM751 / RR501 X10 transceiver;
anyway, the actual transmitter in the keychain remote is a design that
is pretty much standard to X10 products, and is found with small
variations in the 5/6 - in - one remotes, the palm pads, the CM17
Firecracker etc.

The loop, alongwith the copper trace on the PCB acts like an antenna.
There are also articles that describe the X10 RF protocol URL'led from
Ido's site.

Regards,

Anand Dhuru

 

I thought it was an antenna too, but am I wrong about the size issue
with antennas, shouldn't they be proportional to wavelength, etc, etc.
This antenna is only 0.5cm...