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What Is 'Part 15?'

Date:2020/10/12 14:16:32 Hits:





What's all this stuff about LowFERs, MedFERs and HiFERs?


Well, LowFER stands for Low Frequency Experimental Radio, and MedFER stands for Medium Frequency Experimental Radio, and HiFERs operate in even higher frequency bands. And they all involve operating radio transmitters under Part 15 of the FCC Rules.

The Federal Communications Commission, which we usually associate with regulating radio and TV broadcasting, amateur radio operators, telephone companies and such, makes provision for some types of radio frequency devices that just don't fall under any of its other rules. This body of regulations is known as Part 15, just one of many Parts under Title 47 of the Code of Federal RegulationsIn recent years, Canada has adopted similar regulations for its citizens... but not quite identical, particularly in regard to certification of low power devices. See links, below, to these regulations as well.


FCC Part 15 rules cover both unintentional radiators (devices such as computers and TV receivers, all of which may generate radio signals as part of their operation, but aren't intended to transmit them); and intentional radiators (such as garage door openers, cordless telephones, wireless microphones, etc., which depend on deliberate radio signals to perform their jobs).It is the intentional radiators which are of interest to us, because by paying attention to detail, we can make them achieve extraordinary results when conditions are right. Although any type of modulation is permitted which will fit in the band, serious experimenters use Morse Code or various digital modes for greatest distance (DX).

Are the requirements hard to meet?


Depending on the frequencies you wish to use, the requirements can involve tremendously sophisticated RF emission measurements. But not always! Among the various sections and subsections within Part 15 are a number of interesting provisions. One permits the use of up to 1 watt of power and a 15 meter long antenna between 160 - 190 kilohertz, in the longwave bands, with no license requirement. Another permits similar operation from 510 - 1705 kHz, in the mediumwave band, with 1/10 of a watt and a 3-meter antenna. Yet another allows operation in a 14kHz-wide band centered at 13.56MHz, with a maximum field strength limit that works out to about 4.8mW into a dipole or a quarter-wave vertical over an elevated groundplane.Experimenters operating under these sections of the rules have taken to calling themselves LowFERs, MedFERs, and/or HiFERs, depending which band(s) they utilize.

Are these serious limitations?
Antennas of these lengths are very, very short (electrically) at their respective frequencies. Efficiency is naturally a tiny fraction of a percent. Under average conditions, with an ordinary receiver, it was not expected such signals would reach more than a few tenths of a kilometer.

However, if one is very resourceful at reducing loss in the antenna system and maximizing efficiency in the transmitter, respectable signals can be detected over longer ranges. Use narrowband transmission modes, such as Morse code or more advanced digital methods, and that range can be multiplied further.
Take considerable pains to couple a good antenna to a sensitive, selective receiver in a quiet location (away from manmade static and stray radio signals), and you multiply that range again.

Listen in winter, when static is at a minimum and propagation is better on LF and MF, and you can achieve real DX! Even with the power limits we're talking about, LF and MF experimenters using plain ol' Morse code in past years sometimes spanned 100, 300, and--rarely--800 miles or more. From time to time, full 2-way QSOs take place over these distances. But with developments in very slow CW and other digital modes over recent years, 1000+ mile reception is not uncommon!While hams often work the world at very low power levels, to be able to work hundreds of miles at these low frequencies, with virtually no transmitting antenna, takes patience, skill, and love of a challenge.

(Consider how static levels increase as you go down the spectrum. By the time you get below 500 kHz, most receivers are deliberately far less sensitive than they are in the shortwave bands. The assumption is that, at LF, you won't be wanting to hear anything but the strongest signals over the noise anyway. This is obviously not a valid assumption for LowFERs! They exhibit high degrees of resourcefulness in improving antenna and receiver sensitivity and reducing noise pickup in order to accomplish their feats.)Manmade interference (QRM) is a serious matter in these bands, too. A Part 15 operator must not cause interference to any licensed service, but must accept interference caused by other services.

● LowFERs face interference from strong power line control carriers, the occasional utility station, and European broadcasters.
● MedFERs had a relatively quiet band for a few years, apart from fishnet buoys and Latin American areobeacons. Now, however, the expanded AM broadcast band has largely filled up with its major users (commercial broadcasters), along with Travelers Information Service and Highway Advisory Radio transmitters.
● HiFERs are surrounded by leakage from diathermy machines and other users of the Industrial, Scientific, and Medical allocation at 13.56MHz.

LowFERing and MedFERing is not for the faint-hearted, but it can be a lot of fun. And, as long as you keep emissions within the assigned band, you can try all sorts of non-standard modulation methods. While many of these experimenters are also licensed hams, many others are not. Yet we can all hone our technical and operating skills in ways that would otherwise only be possible in the ham bands...and maybe not even there in some cases.


You can view the detailed Part 15 here>>Part 15


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