RF exposure
And what about RF radiation and electromagnetic field safety when all
those power lines carry the broadband signals ?
Maybe a stupid question.............
Jos on4kj
----- Original Message -----
From: "Bill Fuqua" <wlfuqu00@uky.edu>
To: <towertalk@contesting.com>
Sent: Friday, April 30, 2004 10:22 PM
Subject: [TowerTalk] The Trojan Horse (BPL)
> The Trojan Horse (BPL)
>
> A scaled down version of BPL is available at many computer
stores
> right now. It comes in the from of special modems that use RF
frequencies
> to allow a person to route relatively high speed internet connections
thru
> out their home via the house wiring. HomePlug products worked out a deal
> with the ARRL to program their modem DSPs not to produce any signals in
the
> ham bands. This can be seen in the data sheets of the DSP products
produced
> by Analog Devices just for HomePlug products
> <http://www.analog.com/UploadedFiles/Data_Sheets/35466054AD9975_0.pdf>
and
> look at spectra plot "TPC 8". Or find other examples by doing a google
> search for Analog Devices and HomePlug. Looking at the spectra of the
ouput
> of these DSP chips you will see that no carriers are produced in the ham
> bands. But are produced everywhere else such as the Short Wave Listening
> bands, WWV frequencies, aviation, marine and wether fax frequencies.
> The BPL modems will most likely if not already be programmed to
do
> the same thus resolving most amateur radio concerns. Now for the Trojan
Horse.
> Lets say they do not produce ANY interference on the ham bands.
> And BPL is raised to the level of being a valuable asset to Homeland
> Security and is used in every community. The Power Line companies want
to
> do more than to just get into the internet business and provide service
to
> rural areas. They want to get into the Telephone (VoIP) and
> Paid-Per-View-Movie business. And while doing so they totally control
the
> access thru the power lines to peoples' homes thus giving them a real
> advantage over other ISP companies and even the Telephone companies
> themselves. Now you begin to transmit on 20 meters with your 100 watt
> transceiver and your spouse tells you that the neighbor's telephone has
> stopped working. OOPS, it is a BPL VoIP phone and you are disabling the
> entire area network in for a block. They complain to the FCC who tells
you
> that Homeland Security in a National Priority and you will have to just
> stop what it is that you are doing that disables the BPL network.
> This is a real possibility. The public backlash at the ham
> community along with the current Homeland Security mind fix could cause
> serious changes in ham radio either by FCC rulings or executive order
from
> the President.
> You see, even though it is easy to prevent the BPL modems from
> producing ANY QRM on the ham bands by simple programming it is not so
easy
> to make them immune to overload from ham radio transmissions. The
Analog
> to Digital Converters (ADC) could easily be overwhelmed by the RF
received
> by the power lines and data would stop flowing. The only way to prevent
> this is to have passive filters for each and every ham band on the input
of
> each ADC. And if they were also in the path of between the DAC and the
> power lines it would be even better. But that may add excessive cost to
the
> Modems.
> Presently, the FCC is only looking at Part 15. This has to do
with
> the interference of unlicensed devices to other services. Not how
licensed
> services may affect the BPL modems. The FCC must also set standards for
> BPL not only those having to do with the signals that they may
> inadvertently radiate. These must have various details for the
modulation
> methods ,data transfer protocol, and encryption. They should also
include
> details of how the above filters will be implemented and what will be
done
> to resolve problems between licensed services and BPL.
> However, this still does nothing for the Short Wave Listeners.
HF
> propagation is too valuable to ruin by implementation of BPL. One
solution
> would be to allow BPL to use frequencies above 30MHz and to 80 MHz
> filtering out the range from 50 to 54 MHz thus only adding 2 filters to
the
> Modems. This would reduce their usable bandwidth from 78 MHz to 46
> MHz. And by increasing the amount of power allowed on the transmission
> lines by 6 db they can double their data bandwidth thus taking them back
to
> the same data bandwidth that they started at. Actually a little bit
> better. Another approach would be to increase the transmission power a
bit
> more and limit their RF bandwidth to the low VHF TV channels (56 to 80
> MHz). Increasing the signal to noise ratio allows you do to do the same
> thing as your 56Kbaud modem. You are able to use a 4KHz (actually a bit
> less) bandwidth telephone line to transmit much higher data bandwidths.
But
> only if you have sufficient signal to noise ratio.
>
> Sorry for the long (hopefully non-political) message. And those of you
that
> are sending in last minute comments may consider these technical
suggestions.
>
> A few other comments.
> Shortwave Listeners have been having problems with the HomePlug devices
> producing interference. BPL is likely to be even worse for them.
>
> By the way. A little over 15 years ago some of the power utility
companies
> started running fiber optic cables across the nation with plans to
create a
> new telephone system ,but forgot to get the approval of the FCC before
they
> started. The FCC stopped them cold in their tracks.
>
> 73
> Bill wa4lav
>
>
>
> _______________________________________________
>
> See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless
Weather Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any
questions and ask for Sherman, W2FLA.
>
> _______________________________________________
> TowerTalk mailing list
> TowerTalk@contesting.com
> http://lists.contesting.com/mailman/listinfo/towertalk
>
>
_______________________________________________
See: http://www.mscomputer.com for "Self Supporting Towers", "Wireless Weather
Stations", and lot's more. Call Toll Free, 1-800-333-9041 with any questions
and ask for Sherman, W2FLA.
_______________________________________________
TowerTalk mailing list
TowerTalk@contesting.com
http://lists.contesting.com/mailman/listinfo/towertalk
|