AM loop antenna

[TC Chris]

Greg had lamented being unable to string an AM antenna because he has a HOA that forbids them. Boo for HOAs. But I suggested an AM loop and sent a diagram. I also promised photos, and have searched without success for the ones I took. I managed to find one, a not very good one, by a search of my emails. Let's see if I can paste it in.

The next time I'm home in daylight I'll try to take better photos.

Chris Campbell

[TC Chris]

As soon as I hit "submit" I figured out where the photo are--on a CD-Rom fro film camera days. I'll attach two more, before I added the mahogany feet.

[TC Chris]

In the first photo, the indoor one, I have added the extra loop inside the frame with a twinlead extension and "clothespin" clip for connecting to antenna/ground terminals directly. Also in that photo you see a fine GE P-780 portable, inductively connected (not via the twinlead) by sitting inside the loop. The outdoor photos were before I added the inner loop.

The P-780 was a GE "let's do it right" project--tuned RF, P-P output, and big enough for a speaker that could present good audio.

Chris Campbell

[electra225]

Thanks, Chris! I am considering this for one of my next projects after I get radio cabinets painted. I think I want to be able to rotate the antenna without having to move it. How about using stand-offs between the box with wire wound around it and a lazy Susan setup? That wouldn't mash the wires, but would let me rotate the antenna without having to reposition it. I need to find a few of those clothes pin antenna clips. Those work nice on TV;s as well.

May I also suggest you post the pictures and a blurb on this antenna in "Getting Started". It would be easier to find and access there, for future reference. It looks like it would be the berries for someone like me who is short on room and has restrictions on outside antennas....

[TC Chris]

Thanks, Chris! I am considering this for one of my next projects after I get radio cabinets painted. I think I want to be able to rotate the antenna without having to move it. How about using stand-offs between the box with wire wound around it and a lazy Susan setup? That wouldn't mash the wires, but would let me rotate the antenna without having to reposition it. I need to find a few of those clothes pin antenna clips. Those work nice on TV;s as well.

Compared with repairing, prepping, and painting plastic cabinets, this project is a breeze. The box is easy to assemble; the hardest part of that is getting a 1x4 board that's clear and doesn't bow, crook, or twist. Mine had some twist that I had to force out of it. I used dowels and glue to join the corners to avoid screws or nails that might affect the coil inductively. If you had a nice flat board you could just use triangular glue blocks in the corners, or a biscuit joiner.

Assemble it then make the corner slot cuts for the wires. For finish I used orange shellac, which gives it the color you see in the photos. It dries fast. The mahogany feet on mine are secured on the outside edges of the frame boards so they leave clearance for the wires.

Seems to me that Sal, who used to sell capacitors, had the antenna clip devices. Maybe his successor does.

Chris Campbell

[electra225]

Thanks, Chris! I'll check to see if Tony still has them.

A stupid question, if I may? How did you connect the tuning capacitor?

[TC Chris]

First, the loop's tuning cap (an old AA5 radio tuning cap) is just connected between one end of the loop and the other end. I terminated the loop ends through drilled holes into the frame's inside and to solder lugs screwed just inside the holes. Then I ran wires from the lugs to the cap.

Second, this is embarrassing. I just went to look at the schematic, over in "Chat" under your inside-antenna post. The single-wire loop inside the frame, to couple it to the loop on the outside and then via wires to A/G terminals on a radio, is supposed to have a 470 pF cap in series. Somehow I missed that and did not install it.

The single-turn inside loop is secured with some little screen staples.

I can't take photos right now because my camera battery is charging. I went to make up an order of holiday cards and found that it was caput. Getting that order out is first priority right now.

Chris Campbell

[electra225]

I'm looking forward to building one of these antennas. I dug out a parts set for another project and it has a nice tuner. Thanks for your input on this, Chris.