OldCoot

My Feedback: (47)

Having been in the RF Communications field for 30 years, I would like to offer my 2c concerning the many posts I have read involving the installation of a 1/4 helical wound (Rubber Duck) antenna on R/C transmitters.
First of all I have never seen an FCC Type Acceptance # on any transmitter which has an output power of 30dbm or less. (This translates to roughly 1 watt with a 1/4 wave radiator)
I cannot find a Type Acceptance # on any of my R/C transmitters.
There is, however, an FCC ID# which is issued to a manufacturer for compliance of Part 15.
The FCC ID # on my brand new 9C Super was issued to Futaba in 1996 and applies to the TP-FM-72A module.
I looked up the ID# on the FCC website and it states that this module shall comply with Part 15 within the frequency range of 72 through 76 Mhz. It does not apply to the transmitter system, only the frequency module.

The Smiley antenna is a helical wound 1/4 wave design. It has slightly less gain than a true 1/4 wave antenna. It has a slightly different, but similar, (omni) radiation pattern than that of a true 1/4 wave antenna. It is not base loaded, it is a 1/4 wave helix.
Both standard 1/4 wave and helical 1/4 wave antennas are considered to have an onmidirectional radiation pattern.

That Said !! Here is an excerpt from Part 15 concerning antennas.

(Intentional radiator means Transmitter or Radio)

1) The antenna type, as used in this paragraph, refers to antennas
that have similar in-band and out-of-band radiation patterns.

(4) Any antenna that is of the same type and of equal or less
directional gain as an antenna that is authorized with the intentional
radiator may be marketed, and used with, that intentional radiator.
No retesting of this system configuration is required.

Keep in mind that this also holds true for transmitters that do require Type Acceptance as well.
In the telemetry and communications industry we use many styles and types of antennas on common equipment. All without violation of Part 15.
The key is that you can't increase directional gain from the original, nor can you drastically change the radiation pattern.
You can increase gain, if you wish, as long as the radiation pattern does not change. The qualifiying term here is Directional Gain.
In other words you can't put a 3db gain directional yagi antenna on your R/C transmitter, but you could install a 3 db gain omni antenna.
With the helical 1/4 wave antenna, we have slightly less gain but we still have in essence an in-band and out-of-band omni radiation pattern.

I don't know if AMA rules on this matter coincide with FCC or not, but, I am confident that the installation of a Smiley antenna has broken no FCC regulation and that my radio is still compliant with Part 15.

Bax

My Feedback: (11)

The FCC Type Acceptance authorization can be found at:

https://gullfoss2.fcc.gov/prod/oet/c...ericSearch.cfm

Just key in the FCC ID number from the back of your transmitter, and you'll see that the equipment authorization will appear. At the top, it states that it is a type acceptance.

All R/C transmitters are below 750 mW of power, and some are 300-400 mW.

OldCoot

My Feedback: (47)

BAX,

Thanks for the info !!!

mr.rc-cam

"Type Acceptance" was officially discontinued in 1998. It has been replaced with the Verification, Certification, and Declaration of Comformity rules. The FCC Reg ID, found on the TX (or RF module) is an example of certification. In the old days, this was a formal record of Type Acceptance.


FWIW, R/C Tx's are Part 95 devices, not Part 15. It would be best to look at those FCC rules instead. In some regards, they are more strict.

Bax

My Feedback: (11)

From mr.rc-cam: "The FCC Reg ID, found on the TX (or RF module) is an example of certification. In the old days, this was a formal record of Type Acceptance."

That's correct, it does depend upon when the Grant of Equipment Authorization was issued...the new Futaba 14MZ has a certification. Older equipment will have a Type Acceptance...but they DID have a Type Acceptance.

OldCoot

My Feedback: (47)

My Bad for quoting the incorrect reg. (hence the name OldCoot). Always old, somtimes confused !!
However, after reading 95.221 I still don't see any rub with changing antennas, but it may come down to interpretation.

MustangFan

With all that said ( and I believe you are correct ), what will the FCC do if you use a smiley antenna.
My guess is, they could care less.

The AMA might care, if they can use it to get out of an insurance claim though. ( My interpretatation )

From what I gather, the smiley antenna works well ... or well enough for our purposes.
Was considering purchasing one myself.

Thanks for the info, sounds like you know what your talking about.

Darryl Usher

Well I got one (Smiley) and tried a ground check. The full antenna gave more than 3000' and the Smiley gave me 400'. I would not fly this.
Transmitter is a MPX 4000.
Darryl