Re: CM11A hangup: Any better products?

[nobody@xxxxxxxxxxxx (Dave Houston)]

It is ABSOLUTELY so! All of the X-10 made PLC transmitters for which I've
seen schematics (and looked at their innards) with the exception of the most
recent RR501 (last 7-8 years?) use an LC controlled transistor oscillator.
You can see the circuit in the schematics for the TW523, CM11A, CM15A,
TM751, mini & maxi controllers. etc. If you need URLs, I can supply them.

PLC transmitters made by SmartHome and other manufacturers may use
resonators and generate the PLC carrier with a PIC - I haven't seen many
schematics for them.

The most recent RR501 does generate the 120kHz with the PIC _BUT_ the PIC
itself uses an LC circuit instead of a crystal or resonator on its OSC pins
so it's unlikely to be any more tightly controlled than the others.

The same is true for all of the wireless devices.

Europe now has tighter wireless requirements and most of the X-10 modules
used there are fairly recent designs. They do use SAW resonators for the
433.92MHz wireless transmitters but I think the receivers are still LC. I
don't believe they have tightened the requirements for PLC carrier so I
suspect they still use LC oscillators for that.

Joerg <notthisjoergsch@xxxxxxxxxxxxxxxxxxxxx> wrote:

>Hello Dave,
>
>> None of the X-10 modules used in North America use crystals or resonators -
>> all are LC tuned. This is true both for the 120kHz PLC modules as well as
>> for their 310MHz and 418MHz wireless devices.
>
>Well, that's not quite so IIRC. As George said the transmit can be
>generated by the micro controller in a transmitter. All you need to do
>is generate pulses of 8.3usec repetition rate and turn them on and off
>as per the code you want to send. That is very easy to do with a uC and
>I believe that's how the RR501 works. This pulse rate is controlled by
>the crystal or resonator that operates the master clock of the uC. This
>is going to be very accurate.
>
>True, the signal then has to pass the LC circuit. It is, in RF terms,
>usually a "class C" one-transistor stage where the base is driven hard
>by a uC pin. The signal will be reduced in amplitude if the LC is out of
>tune. So it can make sense to also peak this LC circuit to get the most
>onto the line but it won't change the frequency.
>
>> The 1132 circuitry designed by SmartHome is not at all similar to the PLC
>> design used by X-10. I gave a link to a schematic for an X-10 made lamp
>> module.
>
>But a lamp module is only a receiver.
>
>Regards, Joerg
>
>http://www.analogconsultants.com