Built another AM Loop- this one is totally dead. Why?

[modrachlan]

Good Sunday morning,

I made an AM loop over the weekend. I found two loops two different people made- I was confused about exactly how close to make the turns and how many turns to use because these guys both made 24" loops but differ in the number of turns (10 vs 18). I built a cross frame from wood trim, harvested an AM tuning capacitor from an old radio, and used a 90' spool of solid copper hook-up wire from radio shack (24 gauge I think). I made saw cuts where I wanted the turns to be- 1/4" apart. I attached the cap and tried a couple different ways of attaching it to the loop. Three radios, none of which coupled with the antenna at all. Cap or no cap made absolutely no difference.

The weird thing is, I have made them before. I made an 18" loop with 24 turns a few years ago with bare copper wire and a project cap from Radio Shack. That loop was hot. Get any radio near it and it dramatically amplifed AM reception. I gave that one to a friend and thought I'd get around to doing it again someday- that someday came this weekend. But it's like night and day. 10 and 18 windings both do nothing AT ALL to the radios.

Any ideas? Is the wire wrong? The dimensions, number of turns? Could the cap be useless? I don't think it's the problem- the radio had a warped board and bad output caps, but I could hear it tuning AM stations in fine.

Thanks for any advice.

 

[Boombox]

First thing, make doubly sure you have one end of the loop wire attached to the case of the variable capacitor, and the other end of the loop wire attached to one of the contacts that stick out from the side of one of the tuning gangs.

It's easier than you may think to connect your loop to the tuner wrong, and the tuner won't tune the loop. I've done it by accident before. Even a poor connection can do it.

Also, I have two box crate loops -- one is 1.5 ft square, the other one is 3.5 ft. square, and with each one I needed 22-24 turns to tune the band -- even though one loop is bigger than the other, they still use the same number of turns. The amount of wire used was around 110 ft. That may be particular to a box crate loop, or maybe it's not. I don't know.

So you may want to up the amount of wire on your loop (add more turns)..and see if that makes a difference. I've made several loops over the years, and have found it's much easier to use too many windings and cut down to size, than use too few and have to add wire.

 

[modrachlan]

So you may want to up the amount of wire on your loop (add more turns)..and see if that makes a difference. I've made several loops over the years, and have found it's much easier to use too many windings and cut down to size, than use too few and have to add wire.

That makes perfect sense. Good advice, thanks.

I'll double-check my connections, and try more turns.

 

[modrachlan]

update, i rewired using 30-gauge magnet wire with 25 turns. it is wired correctly. still getting bad results. oh well. maybe conditions are just bad today.

 

[Boombox]

Conditions haven't been terrific, but a loop should at least boost the static in your radio.

If you still aren't getting any results, i.e. the loop doesn't seem to affect any of your radios, I'd try running the windings closer together, see if that makes a difference. Spacing can affect the tuning.

That doesn't work, maybe try larger gauge wire?