Re: Need some antenna advice (for my CM15A, of course)

["Robert Green" <ROBERT_GREEN1963@xxxxxxxxx>]

"Dave Houston" <ydobon@xxxxxxxxxxx> wrote in message

>>The RSSI measurement of the receiver linear output made with the
>>BX24-AHT wasn't really useful for making definitive comparisons
>>between antennas because the RF receiver module had AGC which
>>reduces the gain as the signal gets stronger. It was useful for fine
>>tuning the receiver. Lacking expensive lab style equipment, the
>>most reliable measurement is to compare range.

I see.  Sort of like a VU meter on an AGC tape recorder always showing a
strong signal as long as the source is within a certain range.

As long as the distance tests are rigorous enough, they're what really
counts to the end user.  It's just that in so many posts I see less than
optimal testing procedures.  I would assume you'd have to take a least four
different readings (one from each compass point) to make even a marginally
useful range map.

> I forgot that one of the pages on my web site has some screenshots that
> might be helpful in understanding this.
>
>       http://www.mbx-usa.com/rf-noise.htm
>

Yes, thanks.  That's very informative and leads me to wonder how UPB handles
noise. At the site above you wrote:

"Closely spaced pulses affect the AGC and the capacitor on the comparator
input differently than widely spaced pulses."

What do UPB pulses, which (IIRC) are variably spaced, look like to an X-10
transceiver?  It's alleged that UPB works with everything except  the Lutron
Homeworx product lines.  I wonder why?  There's some interesting reading at:

http://www.hometoys.com/htinews/jun04/articles/upb/upb.htm

where they say: "Case Study: Web Mountain has installed UPB devices in
approximately 15 homes. With the exception of one outlet in one large house,
we installed the devices, powered them up and they worked. The one outlet
that didn?t work was fixed by adding a phase coupler. No noise filters were
needed and no troubleshooting was required. Only one of the 15 homes (>6500
sq feet) required the UPB phase coupler."

> I did make comparisons between antennas by running tests where the
> antennas were placed in the "same" location and I sent signals from
> certain locations about the building, always using the same Palmpad and
> using the "same" locations. The locations were far enough away from the
> antenna to guarantee a moderate signal level. From these it seemed clear
> that the eggbeater was better but there are too many uncontrolled
> factors to supply a definitive percentage of "betterness".

Your test setup seems quite rigorous so I'm assuming yours are real-world
estimates, unlike the overly optimistic figures given by X-10 and some X-10
enthusiasts.

Have you ever looked at Leviton's HCPRF All-housecode transceiver with the
built-in lamp control module?  It's got a little wire pigtail antenna that's
not very effective.  It's a unit that can certainly stand a "hearing aid" of
some sort but I believe it's based on the older, AC hot = ground principle
because the insulated pigtail has no shield - just a single wire connected
to the PCB.

I took it off line a month ago in an effort to stop a collision problem I
was having.  Unplugging the transceiver stopped the problem, but it
reappeared a month later.  More detective work required.  I am frustrated
because I have reached the limit of what my trusty ESM1 can tell me about
the powerline signal.  Today, I saw a 1.4V good signal followed by 1.4v
noise followed by a .40 good signal after using a  credit card RF X-20
transmitter.  Very repeatable.  Very weird.

I'm wondering if I should buy a used o'scope or pony up for one of the
signal analyzers.  Any suggestions?  Both Lynx and Monterey look like
they'll give me at lot more useful information about the boogie men in my
X-10 setup.  I bought a dozen new filters and am determined to clear the
lines of all the noisemakers and signal suckers.  It just seems that it *is*
possible to have a fairly reliable X-10 system because enough people manage
to do it.  If a better meter or o'scope doesn't work, it will be time for
Zigbee!

Thanks for all the work in putting those pages together with screen shots,
etc.  It really helps explain what's been a pretty amorphous concept.  Do
you think you might ever do a similar analysis for UPB?  I'd really like to
know whether their "Pulse Position Modulation" scheme is as robust as they
claim.

--
Bobby G.