Part 15 AM antenna

This may be useful: LL-1001-396, 600-1600 kHz Omni Antenna

This one can handle a little more juice and can be built for a specific frequency: LL-1001-396-CF

RFB

Wow, RFB, this antenna is a really interesting find. It is radically different than other AM / MW antennas, being so compact.

Is it good for vertical polarization?

The antennae linked to above are described to be "enhanced loop". Note the horizontal polarization.

Neil

I believe that antenna is just a horizontal loop for receiving, and a really good one ... But although you could certainly use it for transmitting, that'd be only a secondary function. You won't get much range, there is no proper way to load and match.

I built a stick antenna (copper pipe) and 4" dia. PVC drain pipe loading coil wound with 18 awg wire for about $50 US. With proper TX grounding, say 16 @ 10' buried radials, it should serve any Part 15 TX quite well.

Tuning is another whole game:

1) One member lightly sanded the surface of the coil winds and used a brass stylus, very cool idea IMO. Check out Carl's Low Power Hour #10 ... umm ... hmmm ... I guess he's reorganizing the site, can't find it. I'll air it tomorrow morning @ 11;00AM PDT. http://fhtinyradio.com/

2) Variometer, a small turnable coil inside the main coil. http://www.northcountryradio.com/Articles/variomtr.htm

3) Variation on the above scheme, sliding a 5-turn inline coil on a plastic shaft.

4) An inline variable air cap. http://home.comcast.net/~filebay1/1610.html

5) The main standby setup, a copper tube base loading coil type,like this mod. http://www.sstran.com/pages/COMMON/SSTRAN_antenna_with_in-line_coil.pdf

... and more ...

You all would be quite surprised at what that loop will do matched to a 50 ohm TX like the TS-100, or a TH/iAM.

Its also an excellent candidate for a low profile "fill in" antenna where a vertical and grounding system is not practical.

RFB

Hi RFB, am very interested in this unusual antenna and wonder if you have one or have tried one....

Would enjoy hearing a description of the experience and possibly even seeing a sketch of what's inside.

THOUGHT: If it were side-mounted would it become vertically polarized?

RFB - can you enlighten us? It's an expensive alternative, but if it works, it would be good for apartments, etc. Have you done drive tests for range? If so what were the results.

"THOUGHT: If it were side-mounted would it become vertically polarized?"

Mount 4 of them through a power splitter in a circular pattern on the mast/tower.

"Have you done drive tests for range? If so what were the results."

In a situation where there is no ground, that antenna is comparable to an Isotron for range.

It's a plug and play solution without having to build a matching network to take high impedance outputs down to the 50 ohm impedance.

Won't be the antenna of choice for all setups, but is an excellent alternative for those situations such as apartments and condos and even those nasty HOA/CCR situations. One of these antennas and a little creativity and they will never know its there.

RFB

"Mount 4 of them through a power splitter in a circular pattern on the mast/tower."

Not sure which way you mean ... also, 4 would describe a square, eh? I wonder how many could fit within the 3 meter limit. Almost $600 ... Guess someone would have to sell the rest of their gear to get 'em paid for 😉

"One of these antennas and a little creativity and they will never know its there."

KEWEL! A Part 15 Stealth Antenna!

THOUGHT: If it were side-mounted would it become vertically polarized?

Yes, but a loop antenna is directional and would produce two major lobes and nulls in the horizontal plane. Hence RFB's suggestion to mount four on a mast which I assume is to fill the voids. I also assume the number four is to provide a 50 ohm load by connecting two in series in parallel with the other two in series.

There is probably nothing magic in this design. It is most likely a multiturn loop with a tuning capacitor and impedance matching transformer. This is just supposition based on loop designs I have seen.

Neil

If relatively small loops can be used for low power transmission, why don't we have more information about specific models or do-it-yourself designs?

Loops get mentioned, but is anyone transmitting with loops?

"a loop antenna is directional and would produce two major lobes and nulls in the horizontal plane. Hence RFB's suggestion to mount four on a mast which I assume is to fill the voids. I also assume the number four is to provide a 50 ohm load by connecting two in series in parallel with the other two in series."

Bingo and Bingo!

"There is probably nothing magic in this design. It is most likely a multiturn loop with a tuning capacitor and impedance matching transformer."

Partially correct. It is a multiturn loop, but there is no tuning cap or matching transformer. It was not easy opening it up, which ruined it so I had to buy another. But this thing is simply a loop of wire layered like pancakes stacked on top of each other and forming the circle. Oddly enough, each stud from the center to the loop inner edge carries a connection wire, so all 4 studs contain a connection to the loop and all 4 connect to a center stud which is connected to the input center pin.

RFB

Also loop antennas are magnetic, easier to load than electric.

I couldn't find a size ... what size are these things?

About 1.5 foot diameter, and about 8 inches from bottom to top of loop. Loop thickness is about 2 inches.

BTW, this thing is encapsulated in epoxy inside, and is why when opening it up, it ruined it. Fortunately the epoxy is clear so I could see what was what.

Got plenty of magnet wire now! 😀

RFB