Dick,

I'm not at all sure who uses what spectrum in the areas where they are
testing BPL, but I'd bet coffee for a week that those folks studied the
situation carefully before proceeding. Where did they test (I don't know of
all areas and I'm asking a sincere question)? The "promise" of BPL is to
serve areas that are not served well by cable or DSL. Did they test a
fairly substantial area in the country where they could demonstrate
far-flung connections to the BPL, or did they test in densely populated
areas that are already served by various broadband connection (where fire,
police, emergency, etc. are very likely not on low band VHF)? Also, FM
broadcasting is usually located near large population areas (since signals
tend to die off pretty quickly after 40 or 60 miles). This means that if
you have BPL in a city, it is unlikely that residents will experience
capture effect on the FM receivers since they will be getting *huge* signals
on their FM receivers. I note the "neon sign" comment in the thread. Neon
signs are usually found in cities. Those test sites are likely located
either in a city or in an area where the money interests already checked the
FCC site to ensure no low band VHF use by police, fire, ambulance, etc.

Any thoughts on this, or am I crazy?


73 from Rochester, NY
Jim AA2QA


"Dick Carroll" wrote in message
...

Before I retired I was a field engineer working with a statewide
public safety organization which uses low band VHF for base to car
communications statewide, and that system is still virtually as I left
it nearly 10 years ago. I have learned that they are aware of the BPL
docket and filed in opposition, and have some idea that it will impact
their communications, but I wonder if they have a clear view of what
looms should BPL be widely implemented. While working I spent
considerable time on RF noise issues, and I am rather sure that such a
radio system cannot coexist with BPL.

What happens is that when the noise intererence reaches a certain
level, in a FM receiver the limiter saturates, and even a strong
on-channel signal will not cause the squelch to open. The reciever
remains quiet, and the call is unanswered.
I was able to locate one troublesome noise source which was reported
as repeater trouble in that the repeater would ocassionally go quiet in
mid-transmission when a car was calling in. By the time I would drive
the substantial distance to the repeater, a thorough checkout found no
problem with the repeate equipment whatever. After several fruitless
trips and attempts to find the trouble, I finally happened to be onsite
when the trouble appeared, and it was all limiter saturation. Looking
around outside while the noise was present in an attempt to spot a
source in the local rural area, I soon found it- an arc welder in a shop
several hundred yards away. When the welder was in use, the arc caused
noise that saturated the receiver limiter, effectively shutting down the
repeater. We relocated that repeater to a more isolated site where it
still functions as intended.
That example is but one case. BPL will, following power lines, also
follow roads and streets since power lines follow streets and
highway/road rights of way everywhere - the same places where police and
highway patrol units'communications are active. The interference issue
simply WILL cause something drastic to be implemented, what I don't
know. If common sense has anything to do with it, BPL will be sent
packing. Widesp[read implementation of BPL spells the end of lowband VHF
use by public safety organizations. And with states' budgets in the
deflated condition they are in most places, the funding will not be
available to replace those systems in the forseeable future.

I just called a former co-worker who is still working, and asked him
if the organization knows that there is a BPL test site in the state.
He said they did not. I suggested he might want to pass the word on up
the chain so that they might want to send a mobile unit into the test
area to get firsthand information on just what the effects might be. I'm
also passing along all the info I've gathred here and from other
sources. We'll need all the help we can get on this turkey.

In short, I'm coninced that while APCO and others may know
of the BPL docket I wonder if they have a very clear concept of
what it will do to them where low band VHF is used.
For instance, what have you heard from the state of Calorfinia, which
is reported to use low band VHF for their statewide Highway Patrol, and
has over 5,000 mobile units with no telling how many base stations?
I have heard nothing whatever from anyone there on BPL.

It seems evident that the BPL people are not publishing the existance
of these very small test sites any more widely than necessary. So, they
won't garner very many,if any, BPL-specific complaints, will they? And
they'll be able to say "We must not be causing destructive interference
since we haven't generated complaints". Of course limiting the numbers
of users in test areas to a very few drastically limits the amount of
interference potential. With so few BPL users online there *won't* be
much interference caused, thus few or no complaints. Then they will
conveniently pass over this fact, and the decision makers won't know the
difference.

Someone with clout needs to take them to task with the FCC and force
them to use much broader test areas with much more realistic noise
levels generated so that a more realistic noise picture can be
evaluated. As it stands, they may well get what they want by default.

Dick W0EX



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