* TWO: We need more technical showings this time, with as many solid
details as possible. I hope the Part 5 licensees are prepared to crunch
numbers, but those of us who only monitored are also able to contribute.
(Much more on this in future correspondence, I expect.) In par. 169. the FCC enquires: "to meet our goal of providing for the coexistence of amateur services and PLC systems in these bands, we seek detailed comment on the technical characteristics of both the PLC systems and the amateur stations.
This information will allow us to set an appropriate separation distance."
The very next sentence, though, I recognize as a somewhat worrisome bit of FCC-speak: "Although the Commission in the WRC-07 NPRM inquired into the technical rules and methods that would assure coexistence, commenters provided little in the way of concrete information." Read that as said with a slightly scolding tone, but with a facial expression that says they're keeping an open mind.
The utilities, IMO, provided no concrete technical information at all. ARRL
cited the 1985 NTIA study on which the 1 W EIRP and 1 km separation idea is based, but the FCC is concerned whether that's still valid. Well, one would hope that any changes made to PLCs over the past 30 years would be toward making the system more robust, not more vulnerable to evildoers, accidents, and natural disasters, but this could prove an area of contention. That may be something the big guys have to fight out; I don't know how much we as individual licensees or observers can contribute. But there ARE other technical matters the FCC needs and wants to know, which we may be able to furnish.
For instance, what sort of PLC signal levels have we actually experienced in the proposed bands? How serious were their impact on licensed activity, and how have PLCs been coped with in actual operation? Also at paragraphs 171, 178, and 178, the FCC is asking for some really fundamental, crucial data.
Namely: What sort of power levels have the Part 5 licensees actually
radiated, and at what actual separations from transmission lines? What
maximum size should an amateur antenna be, and--the biggie, in my view--what is the efficiency of both "typical" and potential amateur antenna systems?
(The Commission would like us to include information from Canadian and
European hams on these issues as well. Details of amateur practice in the
rest of the world could be very helpful in formulating rules here.)
Those operators who have the capability of measuring their true field
strength are in an especially excellent position to help quantify current
practice. Those who can't do that, but are able to measure their ground
losses accurately, can make reasonable calculations to show the maximum
efficiency possible with antennas of various heights. That's likely
preferable to doing it all in NEC modeling, since not all such software is
really good at predicting ground system losses, especially at LF. I'll
gladly offer my own ground system's resistance numbers to anyone who wants to do the math, for instance, as its 32 radials of 104 to 135 ft length in 15 mS/m soil are probably representative of a fairly decent ground for
antennas up to 100 feet high...and I'll be doing another set of readings
very soon, which can include measurements at 2200 m this year in addition to the runs I routinely do at 1750 m.
* THREE: At 172, the FCC observes: "If we were to adopt our proposal to
permit amateur operations only when separated by a specified distance from transmission lines, when a new transmission line is built close by an
amateur station, the station either would have to relocate farther away from the transmission line or cease operating." Scary, huh. But they go on to ask: "How should our rules address the potential for new transmission lines to be constructed closer than the specified distance to pre-existing amateur stations? We do not want to inhibit the ability of either PLC systems or amateur services to grow and expand without imposing unnecessary burdens on either. Is it possible for utilities to refrain from geographically expanding their PLC operations within the relatively small portion of the 9-490 kHz band that we are making available for amateur operations, and is this something utilities would do on their own accord, given the Part 15 status of PLC systems? Should our rules explicitly prohibit utilities from deploying new PLC systems in these bands?"
My answer: yes, please. Look back at par. 26, in the WRC-07 R&O section
where the Commission explains their basis for adding the 2200 m allocation:
"We intend to structure these service rules to promote shared use of the
band among amateurs and PLC systems. Amateurs will not be able to use their allocation status to force unlicensed PLC operations out of the band, and utilities will have no cause to abandon or incur large costs to modify
existing PLC systems." Read that again: "Amateurs will not be able to use
their allocation status to force unlicensed PLC operations out of the band."
That's the reality of the matter, and yet I think it also works in our
So far as I know, this situation is unique in the history of radio regulation. I can't think of another example where an incumbent, but unlicensed and unallocated, user of radio spectrum has been afforded such protection from any allocated and licensed service. However, most of us who commented in the 2013 proceeding DID AGREE with the Commission that PLC technology has been a special case for a long time, and most recognized that acceptance of its existence was the only way to move the discussion off dead center and get to the point where we are now.
But I maintain this coin has two sides. If we in a licensed, allocated service are willing to accept that we cannot displace existing PLCs now or in the future, then it is ONLY FAIR that the unlicensed, unallocated users should not be able to displace the licensed users, either, now or in the future. Otherwise, it is not truly sharing.
The only way I can see to guarantee protection to licensed users, comparable to what the unlicensed ones will have, is to incorporate within Part 15 a prohibition on any changes in power, transmission mode, and route of existing PLC systems, or installation of new ones, within a reasonable band centered on the new amateur allocations. That achieves the stated goal of not displacing existing systems or burdening the utlities by forcing any changes to them, while only removing two small slices of spectrum from consideration for future installations. That seems an entirely reasonable compromise to me.
Your comments are welcome--and essential!
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