[TowerTalk] The Trojan Horse (BPL)

[Bill Fuqua]

                                         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