Part 15 Intentional Radiator Rule Making Suggestion
Posted on December 20, 2007
I really think that the FCC should review their rule on the intentional radiator for use in section 15.219(b) ” The total length of the transmission line, antenna and ground lead (if used) shall not exceed 3
Since the radiator that is 3 meters long is way too inefficient to do something like provide effective radiated power output via gain in the Medium Wave Band. It can be improved as the SSTRAN antenna design shows us (based upon various Internet forum and blog comments), but this does not make it a problem for any reason. Improvements to the antenna of this height will not ever make it an efficient radiator, though it would be improved from the stand point of the Rule as it is written now. The thing then that would be of use only to those of us who are using Part 15 transmitters for community broadcasting would be the use of coax cable on the antenna of any length we need. And keep the radiator length the same. Hence the radiator can not exceed 3 meters height above ground. And the coax should be buried in the ground out to the antenna so as not to become a radiator source. And hence meet with the current vision of the Rule, but it can be extended some since our power level is not ever likely to create any problems.
Also it would be nice to have such a Rule that would allow the use of a loading coil at the base of the radiator. And a small capacitance hat of the solid disc type of maybe 3 foot diameter. And a three foot long ground extension at most. Hence we could improve the antenna though it can never become a truly efficient radiator, just better than the one in the Rules.
Rule 15.219 (b) is suggested to read then as follows: “This Rule for the intentional radiator system for use only with a Part 15 community station of 100mW as a small broadcast station only, shall only apply to such a station and shall not be for use with any other Part 15 device of the “unintentional radiation types” and herein only applies to this section herein of 15.219. Wherein such a station may use coaxial cable of any length to the intentional radiator, “so long as it is buried out to the radiator site.” And hence can not be considered to be radiating above ground. And if unable to be buried, it then shall not exceed 15 foot in length if used in a building where the station is up on a higher floor, or if in a single level building that has no outside ground area, such as is covered by a parking lot. A radiator on a building then above ground will be shorter then the following ground based radiator.
The ground based radiator itself at the coax cable end shall not exceed 3 meters height above ground. And may use a base or midsection loading coil, or may be made as a helical radiator. And may include up to a 1 meter diameter solid disc type capacitance only, atop the radiator. A toroid capacitance hat then shall suffice for this or a flat aluminum disc. Up to a three foot ground extension may be used to ground the radiator’s base and act as the counter feed point connection, so long as the radiator is not more than 3 meters in height above ground.
Intentional radiators for use atop a building shall not exceed 1.5 meters height above the roof. And shall not use a ground from that height, but may be grounded to a metal roof as a ground plane so long as no ground wire from the roof or radiator runs to earth ground. Wherein such a long ground wire would extend the radiators length above ground.
Intentional radiators for use atop buildings shall not be used atop mast or towers. Coax leaving a station to go outside, and then run beneath the ground may have up to 15 foot of length exposed to reach the ground where it is buried. And as stated above, may be of any length beneath ground.
Further, the antenna shall use a matching network at the feed point. And shall not be merely just a tapped coil, which is to say, at the feed point whether it is a coil tap, etc, a LC matching network is required for proper matching as to prevent coax cable outer shield radiation by improper matching. And so, as to help to minimize out of band harmonic content. No antenna then shall be considered type accepted without a proper LC network match at the feed point.
Part 15 devices meant only to radiate around the house, for use with home computers and stereos or other sound sources as a personal wireless system, shall not use this radiator system. Nor can they have a coaxial or RCA jack connection or any other type of connector to connect such an antenna to them. Only transmitters type accepted for use as a small 100mW unlicensed community station shall use this radiator type.”
I think this rule makes sense and is clear. And it provides the FCC with the safe guards it needs for protecting the Medium Wave Broadcast Band. And after reviewing the comments made by people in regards to the use of the SSTRAN antenna design and their rating it’s good signal strength distance to 1 mile with marginal reception at 2 miles under good conditions. I think then that this would pass muster if given a good review. It does not mean it would pass at the first attempt. And so. I would not change the words since if the suggestion reaches the right FCC engineers they will see the fact that the Suggstion when used with a 100mW transmitter is within the vision of the FCC. Now regardless of whether it passes the first attempt or not, it can be suggest later on and then again if needed.
This is the only thing I can think of that the Part 15 stations could benefit by. And since in all of the years of Part 15 stations on the band, going back to the very beginning of radio as you study the history of radio. Part 15 is not a problem and such an antenna would not create an undue problem with the vision of the FCC and the licensed users of the Medium Wave Band.
If you look at Part 15 station owners, you will see people who are as professional and responsible as they can be. And who pride themselves on running a nice clean station with a good signal quality and meeting some good specifications. I would say this, if you have to add an extra rule to the above for helping this idea. It should be one that suggest the use of a low pass rf filter on the output of the transmitter of a minimum of 5 elements. A filter such as meets with the specifications for ham radio or for broadcast stations. It can only help the cause. And would relieve anyone’s fears about out of band interference.
I would suggest that the additional Rule then be made as follows: “The transmitter for use with the above intentional radiator. Shall use either an internal or external rf low pass filter at the transmitter output to the antenna of a minimum, of 5 elements. And meet with acceptable attenuation standards as are common with use in other radio services for high quality out of band signal attenuation.”
I should add that the above antenna types if analyzed in software, show that they are really narrow on bandwidth at resonance. And hence attenuate the side bands of the signal allot. And so, these types of antennas offer some adjacent channel protection by limiting the signals bandwidth and this fact about these antennas should only be considered a plus for making them acceptable for our use.