Total posts : 45366
First, I would like to ask if anyone has ever heard of an actual case where the FCC faulted a part 15er for his antenna/feed/ground lead length being “slightly” over 3 meters? When I say “slightly” I mean inches or maybe a foot and certainly not blatantly longer. I haven’t seen any evidence and I have been watching for several years. I may have missed a report somewhere.
I agree 100% with your “use common sense” statement. I’m sure anyone who has seen a few of the common part 15 am antenna arrangements could easily spot a significant violation of length. I assume FCC inspectors would be even more attuned to this.
In the case of the rangemaster, the coil is not visible inside the box, so it is not likely to even be considered as a contributor to the antenna length. The coil is a toroid type which is very good at confining its magnetic field, so, even with the plastic box, it contributes a negligible portion of the overall radiated signal. No-brainer here. Just measure the length of the whip. Interestingly, the whip could be close to 118 in. and still be legal, but a 118 in. whip is not available off-the-shelf.
Because the Manteca Magnum and the SSTran (and other similar types) have the big loading coil visible externally, the common sense approach is to include the coil in the 3 meter limit. This still allows the antenna pipe to be somewhat more than 102″.
Even in the case of the external loading coil, very little of the overall signal is radiated by the coil (Rich may want to comment here). It would be pointless for the FCC to try to nitpick on dimensions of parts of the antenna that don’t contribute significantly to the radiated signal. In fact, it would be counterproductive to FCC goals to do this. A long, skinny loading coil would require the antenna to be shortened to stay within the 3-meter limit and would not perform as well.
An even more foolproof approach would be to put the big loading coil inside a big grounded metal box along with the TX. Then the coil would radiate nothing and could absolutely not be considered in the 3-meter limit. Then the antenna pipe could be lengthened to nearly 118 in.
We already know the FCC doesn’t bother about the “ground lead” length because they have never faulted a user for elevating their antenna above ground level, which implies that the ground path must be via the mast or a wire.
I hate to go non-technical because I feel more comfortable with facts than politics, but the actual bottom line on legality boils down to:
1. don’t interfere with licensed stations.
2. don’t broadcast offensive or controversial content that may invite complaints.
3. don’t get into a p*ss*** match with a local neighbor who may retaliate with an FCC complaint.
If the FCC somehow does find fault with a serious attempt at compliance they will ask you to correct the problem or stop operation. If you do what they say you won’t get fined or go to jail or need to hire a lawyer.