X10 Community Forum

🔌General Home Automation => Automating Your House => Topic started by: fominhars on March 27, 2007, 04:24:30 PM

Title: Why Carrier is 120 KHz?
Post by: fominhars on March 27, 2007, 04:24:30 PM

  Hello!

  Someone know why the carrier is 120 KHz?

  Thank's.

Title: Re: Why Carrier is 120 KHz?
Post by: dave w on March 28, 2007, 12:24:42 PM

I don't know why 120KHz was selected as the modulation frequency (not really the "carrier") but remember; the 120kHz is only the modulation frequency of the bits or bursts that are modulated on the 120V, 60Hz sine wave.

Since X10 PLC was spawned by the design of an old (late 1970's) BSR programable turntable which used an ultrasonic remote control, it could be as simple as the 120KHz was an easy multiple of the original ultrasonic remote's transmitting frequency. The protocols for the ultrasonic remote later became the protocols for the PLC signals on the sine wave.

This is really a Dave Rye question. I suspect he is one of the few who will remember. On the X10 web site there is a history of X10 and you might find an answer there.

Title: Re: Why Carrier is 120 KHz?
Post by: Brian H on March 28, 2007, 02:16:36 PM

I have not seen an exact reason for 120KHz. Only thing that I did notice is it is an exact multiple of 60Hz power cycle.
120,000/60= 2000

Title: Re: Why Carrier is 120 KHz?
Post by: EL34 on March 29, 2007, 11:37:30 AM

I don't know why either but 120khz being a multiple of 60hz may make it easier to keep the control signal intact
60hz and 120khz would both cross at the 0 hz mark on the sine wave.