Re: XTB-II Options

[nobody@xxxxxxxxxxxx (Dave Houston)]

"Robert Green" <ROBERT_GREEN1963@xxxxxxxxx> wrote:

>"Dan Lanciani" <ddl@danlan.*com> wrote in message
>
><stuff snipped>
>
>> I suspect that it's also fairly easy to fool yourself as I once did when I
>thought I
>> could get multiple RF->powerline transceivers to coexist.
>
>That's what I thought and was the issue that first brought me to CHA.
>
>> With two transmitters and a receiver plugged into a power strip you may
>> well never see a problem (I didn't.)
>
>My experience is that when the transmitters were very close or very remote,
>there wasn't much problem but if the transmitters were just close enough so
>that their transmissions would both arrive at a receiver at different
>strengths, particularly marginal ones, the fun began.   Things actually got
>infinitely worse when I add a Decora AHT to the mix since it seemed to have
>either collision avoidance or a transmission pattern somehow different
>enough from the TM-751's that there were issues.  It caused a terribly
>frustrating problem with the Hawkeye controlled bathroom light turning on
>and then off about one second later.  Boy, did THAT have low SAF!  The
>Decora is now removed and the occasional bathroom light instant turning off
>problem is thankfully gone with it.
>
>As I understand it, there's no guarantee that each TM-751 will begin
>receiving an RF command and begin transmitting to the powerline absolutely
>simultaneously.  Judging by what the Monterey showed, one or the other units
>would begin early, resulting in collisions at a point in the house where
>both signals were received.  I suppose that's due to long button presses,
>marginal RF reception and human body interference because it was sensitive
>to people moving around.
>
>I assume that if the second TM-751 was even one half cycle off in hitting
>the powerline, the two transmissions would "step on" each other.  Since the
>problem seemed to get worse when my wife was home and moving around the
>house (perhaps blocking good reception at the second transmitter momentarily
>or maybe emitting anti-proton beams) it had to be fixed.  I doubt if two
>transmitters on the same strip would be subject to that kind of problem -
>they would see the RF command virtually simultaneously every time.
>
>Thank God for the XTB - now I don't need to use TM-751 as a poor man's
>repeater - the XTB signal is strong enough to couple the phases at the power
>pole, or at least that's the conclusion Jeff and I came to.
>
>I have a TM-751 for each housecode I use and they are all routed through
>XTB's for amplification.  The TM's are located nearest to where they will be
>receiving RF.  The one for the driveway is concealed along the top edge of
>the living room window and oriented horizontally.  It *mostly* covers the
>driveway.  (-:  Every once in a while, nothing I do will activate the porch
>light from 50 feet but it always happens in bad weather so I've been
>reluctant to debug it.  I just activate the keyfob a little closer to the
>house.  We have good streetlights so it's not an issue.  Other TM's are
>placed accordingly and it's very rare now that I see the dreaded "BSC/BBK"
>codes on the Monterey analyzer that indicate a collision or otherwise failed
>transmission.
>
>Say, did you ever set up your mast mounted WiFi-finder cam?

RF receivers have to be about 1200 miles apart for the arrival times of the
RF codes to be off by 1/2 cycle of the 60Hz.

TM751s on opposite phases will _ALWAYS_ transmit 1/2 cycle out of step on
unit codes 1 & 9, guaranteeing PLC collisions. On the same phase, you can
have as many as desired (at least to the point where multiple PLC
transmitters attenuate the signal too much).

     http://davehouston.net/multiples.htm

RR501s and the Leviton HCPRF have collision avoidance. Combine that with the
fact that most of the RF signals are sent 5 or more times and they use
transformerless power supplies that tend to droop when loaded and funky
things can happen which are hard to analyze.

http://davehouston.net
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