I read a lot. Often what I see is confusing or contradicory. With that in mind, can I ask some direct questions that might not have 100% concrete answers? I'm not trying to stir things up, but I'd really like to know what's up.
No mast mounted part 15 AMs because the mast (or tower or billboard frame) acts as a radiator which violates the 3 meter limit?
No multiple transmitters in a micro-cellular arrangement so they function like a higher power single transmitter? Example: cell radius 2500 feet on AM or 500 on FM?
Are base loading coils accepted as a way to make an antenna resonant on AM? Does the coil wire count as part of the 3 meters?
You can certainly have a mast mounted AM transmitter. The issue becomes if the mast is connected to the ground of the transmitter. The 3 meter limit includes antenna AND ground lead. A 30 foot mast would give you a 30 foot ground lead, which is way over the limit. So, most would suggest mast mounted with elevated ground radials, grounded to a metal roof, etc. There are as many interpretations of this as there are part 15 broadcasters I suspect, and also apparently varying interpretations among FCC inspectors, at least according to the manual with my certified transmitter.
And yes, the loading coil counts as part of the antenna I believe.
Tim in Bovey
On the other hand the loading coil does not resonate, for which reason some people do not count its size as part of the 3-meter limit.
Also, if the loading coil is placed horizontal with relation to the vertical whip its vertical length is reduced to a couple of inches, and it works just as well as if it's stacked vertically.
But the full length of the wire used to wind the coil? No. That length does NOT count toward the 3-meter limit. If it counted, coils wouldn't be possible.
I'm just confused.
I'm confused therefore I think.
I think therefore I am.
But... I am WHAT?
I think therefore I am... confused?
- "Better to remain silent and be thought a fool than to speak out and remove all doubt."
- --- Abraham Lincoln
- _________
- The above quote has been attributed to the 16th President of the United States.
- .
- It is good advice, whatever the source of that quote or the subject being addressed.
- .
- Particularly so in the case of Part 15 AM/FM systems if no verifiable proof is supplied or otherwise available to support the conclusion(s) of such public statement(s).
The problem with verifiable proof, be it Part 15 or the IRS is the laws/rules are not stated definitively and are open to the interpretation of the inspector or agent, etc.
You can readily find where FCC inspectors have tagged some for a violation where for others it was not an issue. And it's proven every year that several IRS auditors, given the exact same tax returns, come up with different final answers. I generally find many laws have become so complex that they cannot be enforced equally.
Tim in Bovey