Randall J wrote:
I operate a Part 15 station for my neighborhood (FM) and have acquired
an AM transmitter. I've seen plans for vertical antennas but would
rather make my own from the few parts I have. I have 8ft of aluminum
tubing and would like to make a loading coil using 3 inch diameter PVC
pipe. Given the frequency I operate on (1610khz), 8 ft of tubing, and a
3.5 inch coil form, how many turns of 22AWG insulated wire would I need
to wrap? (Oh the tubing is in two pieces and I can slide the top piece
up and down).

Is there a program I can download to find this out?

Randall

Hi, Randall -

I have some information directly from the FCC concerning antennas for Part
15 (15.219 Operation in the band 510-1705 kHz) which I will share herewith.
My intention is simply informative. I would encourage you to contact the FCC
to clarify your own questions. As you can probably see, you must phrase your
question as if you are a lawyer. My questions were sent to:

I sent the following:

Part 15 regulations says:

[Code of Federal Regulations]
[Title 47, Volume 1]
[Revised as of October 1, 2002]
From the U.S. Government Printing Office via GPO Access
[CITE: 47CFR15.219]

[Page 732]

TITLE 47--TELECOMMUNICATION

CHAPTER I--FEDERAL COMMUNICATIONS COMMISSION

PART 15--RADIO FREQUENCY DEVICES--Table of Contents

Subpart C--Intentional Radiators

Sec. 15.219 Operation in the band 510-1705 kHz.

(a) The total input power to the final radio frequency stage
(exclusive of filament or heater power) shall not exceed 100 milliwatts.
(b) The total length of the transmission line, antenna and ground
lead (if used) shall not exceed 3 meters.


Concerning the 3 meters maximum length for antenna, transmission, and
ground, would a capacitance hat at the top of a vertical radiator be
included in the 3 meter limit?

For clarification: Suppose I put a 3 meter vertical monopole on top of an
existing structure which has a metal roof. The transmitter would be located
at the base of the monopole, so it would require no transmission line. Would
I be allowed to install a 3 meter diameter (or more) top hat? The top hat
would be shaped like a spoked wheel and would serve the purpose of
increasing the current in the monopole through capacitive coupling to the
metal roof ground.

Thanks for your assistance.

John Smith



The reply to this message from was:

"Answer:

The intent of Section 15.219 is for a maximum 3 meter wire antenna.

The total length of the antenna plus ground lead plus connecting lead
must not exceed 3 meters. The rule doesn't permit a 3 meter diameter
"top hat" but should be applied to the combined length of each radial.
If the combined length of each radial added to the length of the antenna
vertical structure added to the length of the ground wire exceeds 3
meters, it would not be permitted."


I then sent the follow up questions:

"Thank you for answering my question concerning capacitive top hats.

I have two other questions about the 3 meter limit in Section 15.219:

Is a 3 meter diameter circular loop antenna allowed?

Is a square loop antenna of 3 meters per side allowed?

Regards,
John"

The reply from was:

"I have two other questions about the 3 meter limit in Section
15.219:

Question:

Is a 3 meter diameter circular loop antenna allowed?

Answer:

No, the total length of the antenna must not exceed 3 meters.

Question:

Is a square loop antenna of 3 meters per side allowed?

Answer:

No, the total length of the antenna must not exceed 3 meters."


The point here is that you must be very specific. I suspect that, if you ask
"Does a one foot diameter loading coil composed of ten turns constitute part
of the antenna specified in the Part 15 regulations?", they will reply that
the length of the wire in the coil is part of the antenna.

It would probably not be anything you should worry about unless someone
complains, but, if you want to comply with the rules, you should ask them.
Try to think like they do, not as if you want to beat the system. You
already know they don't want your signal to go very far.

My post was designed to be helpful, not argumentative. I hope you will post
your own findings here for everyone's benefit.

John
KD5YI