Total posts : 45366
Greg,
You are correct that the rules for carrier current are not exclusively for campus operations but it does appear that they are very restrictive regarding field strength. I have no idea why in the link above they were “shut down” and I can only speculate. For those who are interested, here are the pertenent rules revised Sept. 05:
[quote]
Section 15.221 Operation in the band 525 – 1705 kHz.
(a) Carrier current systems and transmitters employing a leaky coaxial cable as the radiating
antenna may operate in the band 525-1705 kHz provided the field strength levels of the radiated
emissions do not exceed 15 uV/m, as measured at a distance of 47,715/(frequency in kHz) meters
(equivalent to Lambda/2Pi) from the electric power line or the coaxial cable, respectively. The field
strength levels of emissions outside this band shall not exceed the general radiated emission limits in
Section 15.209.
(b) As an alternative to the provisions in paragraph (a), intentional radiators used for the
operation of an AM broadcast station on a college or university campus or on the campus of any other
education institution may comply with the following:
(1) On the campus, the field strength of emissions appearing outside of this frequency
band shall not exceed the general radiated emission limits shown in Section 15.209 as measured from the
radiating source. There is no limit on the field strength of emissions appearing within this frequency
band, except that the provisions of Section 15.5 continue to comply.
(2) At the perimeter of the campus, the field strength of any emissions, including those
within the frequency band 525 – 1705 kHz, shall not exceed the general radiated emissions in Section
15.209.
[/quote]
The field strength of 15.209 is less than that produced (by virtue of the power and antenna restrictions) by 15.219 so it would seem that the 3 meter, 100 mW rules would allow better coverage except this is from essentially a point source where carrier current seems to be OK with a lower field strength but it can be spread along miles of wire. I don’t know of anyone who has done this other than on a campus and maybe someone will volunteer their experience. My city has installed underground concrete conduit and fiberoptic cables which they lease to anyone willing to pay. Maybe such conduits would be available for leaky coax, but again, I don’t know how this would work underground. Outdoor fiber optic cable has two “messenger” wires and perhaps they could be used for RF. Just brainstorming.
As far as tapping into the 13 kV lines, I can think of easier ways to achieve suicide. Also, the RF doesn’t get through the distribution transformers so this system would be back to the radiation limits mentioned above. It may work but I don’t think it is worth pursuing.
Here, there is one transformer for two houses. There is a 22 kV. 3 phase distribution trunk 4 feet underground in my front yard and I have to wonder if I could detect a RF signal if it was on this trunk. Fun to think about but not workable here.
A leaky coax system may work if one could get permission and bear the cost of installing the coax on the utility poles. Maybe I am thinking small but I would not even pursue it. Perhaps it makes more sense to stream on the internet?
Just some stuff to think about.
Neil
