Some time ago I set out to build an AM loop antenna from a 14" embroidery hoop. Using one of the formulas available somewhere, I put 17 turns of #28 enameled wire side by side, then set out to find an old radio to salvage a variable tuning capacitor, as it didn't appear to have much effect when connected directly to the ant terminals on a CCRadio.

Fast forward about 2 yrs and many detours later, I finally got a nice VC from a Grundig radio. Connected the loop to it, experimented with an old transistor radio and was able to get some stations to come in more clearly, but not as much improvement as I expected. I haven't tried adding a second pick-up coil as most of the radios I want to use it with don't have ant terminals.

So, I'm wondering if there's a problem with the way I wrapped the loop or the type of wire I used. I placed the wraps of wire side-by-side, closely packed. Should I have spaced them apart a bit? Or used heavier wire with insulation?

I suspect that the calculation is correct if you are indeed using a variable cap designed for the broadcast band. I have one small commercial loop that has a 9" coil and is wound with 28 turns of something like #26 enamel coated wire, closely spaced.... Pix 1.

I have constructed several loops, such as the 2 foot (diagonal) loop in Pix 2.
It has 18 turns of # 22 wire, spaced about one wire diameter. It has a 1 turn coil in the the in the center, between the other turns, for pickup. The pickup coil is helpful, as connecting a radio directly to the tuned loop reduces its "Q" and causes the tuning to become rather broad and reduces the improvement provided by the loop.

It may be that your environment is noisy from computers, lamp dimmers tv sets, battery chargers and other common household items that produce interference, and pretty much render the loop useless, as it picks up more noise as well as additional signal. Get away from the house and see if the loop works better. For most AM DXing, I use an outdoor loop (about 4 1/2 foot diag. 8 turns #14 wire) located about 75 feet from the house. It can barely be seen from the "radio room"... hint: the cross arm is directly behind a hummingbird feeder in the "woods". Pix 3.... Unfortunately, there are a couple of "solar dryers" located very close to the loop, which mess up the sharpness of the directionality somewhat, but it still beats using something indoors.:yes:

I added a close up pix of the outdoor loop... the 1 turn pick up loop can almost be seen at about 2/3 the diagonal of the main loop. I experimented with several different sizes for the pick-up coil and chose a configuration that yielded decent signal strength without reducing the "Q" too much. Many times, mostly in the summer, I will park my Icom on the small table in front of the loop, and operate it from a 12V lawnmower battery, to further reduce interference from sources in the house. I have an additional capacitor mounted in a box below the loop, to tune below the broadcast band. Last winter, I nailed several Long wave stations from Russia! These were on 153,189 and 279 kHz.
jr

Hmmm... we do have a lot of noise from the AC lines in our house, most of it coming from our neighbor. I'll give it a try out side. At least that might tell me if the loop works... or not.

I'm still unclear about the spacing of the wires in the loop... should they be spaced apart? Or does that not have an effect?

Thanks.

I'm still unclear about the spacing of the wires in the loop... should they be spaced apart? Or does that not have an effect?

Thanks.

As A DXer, I prefer spacing the turns, as IMHO, this configuration produces higher "Q" which yields sharper tuning and better nulls. Much of the time, when DXing, the loop is aimed to "null out" an interfering station rather than maximize the gain on the desired station.

A suburban listener, desiring to improve reception of semi-local stations, might be well served by a broader tuning, less critical loop, that may provide a bit of improvement on several stations, perhaps without re-tuning when the station is changed.

Note: Many larger portable radios, such as the CC radio, GE "Super Radio", Sony 2010, Panasonic RF-2200, Grundig S350, and similar larger portables contain a fairly large "loopstick" antenna, and show little, or no improvement when used with a smaller loop, like the one in my first picture.
jr

Greetings: I bought a Select-a-tenna at a thrift shop for a buck in like brand condition.They asked me what it was. I replied that it was a passive antenna for an AM radio. You are right that it doesn't do a thing for the GE Superadio.

Dieseljeep wrote: They asked me what it was. I replied that it was a passive antenna for an AM radio.
(Their response, no doubt: blank open-mouthed stares! :D )

it doesn't do a thing for the GE Superadio.

I'd guess it probably won't do much for a CCRadio either then...

As A DXer, I prefer spacing the turns, as IMHO, this configuration produces higher "Q" which yields sharper tuning and better nulls. Much of the time, when DXing, the loop is aimed to "null out" an interfering station rather than maximize the gain on the desired station.

A suburban listener, desiring to improve reception of semi-local stations, might be well served by a broader tuning, less critical loop, that may provide a bit of improvement on several stations, perhaps without re-tuning when the station is changed.

Well, I'm 20-75 miles from any local stations and 150 or more from the ones I want to hear, so would spacing the turns slightly work better for me?

Try looking for a Kiwa MW Loop...Tiltable, steerable, tunable...I'd about give my guns up before I would my Kiwa...(grin)

Well, I'm 20-75 miles from any local stations and 150 or more from the ones I want to hear, so would spacing the turns slightly work better for me?

I think that in that situation, I would use a fairly large loop (2-4 feet) with spaced turns. One nice thing about this hobby is that wood, pvc pipe, and wire are inexpensive, so you can build several different designs and determine which is best for your application.
This builder even makes his own capacitor:
http://www.youtube.com/watch?v=VPALB-ZZGbY

nice 4 footer here:
http://www.youtube.com/watch?v=HXQeZxeCJ2c

2 footer here:
http://www.youtube.com/watch?v=QpGXECoY6zg&feature=related

Another:
http://www.youtube.com/watch?v=l_keFgFYkO0&feature=related

The ability to tilt the loop like the Kiwa is a desirable feature. Sometimes I end up with one of my home-made loops propped up at an odd angle to better null out an offending station.
jr

The R-389, the R-390s & EK-07 all LOVE the Kiwa...Took it over to a friend's house one Sunday afternoon in the winter-He has a late Thirties cathedral style radio that would barely pick up anything at his location...He thought his radio was sick, even tho he'd recapped it & checked the tubes...It "Came Alive" once we hooked up the Kiwa...Little 1KW daytimers up in Virginia & Kentucky popped out of the woodwork..Ratshak had a very good tunable loop several years back, & at $20, IIRC, it was better than one you could make yrself...Took some "Shade-tree" mechanic-ing, but it made a good showing of itself against the Kiwa...Naturally, when I went to grab a couple more, they'd been discontinued, so typical of RatShak...Excuse me, CELL-FONE Shak...(grin)

Is the Kiwa loop still available? I just checked Universal Radio and did not find it.:no:

jr

Naw, it got axed several years back, too...IIRC, I gave $350-400 for mine brand-new...But its almost MAGIC in how well it works, especially w/ a super-sensitive receiver like a 390A...But they DO have a "Pocket Loop" which will fold up & fit in yr pocket-Call 'em at 507-634-6134, & it works all the way up to 23 mHz, so you get most of the shortwave spectrum, too...

I have a TERK passive loop and it works well on my Radiola 60. It's called the Advantage. Two wire connection and inductive if you wrap the radio with the wires. $35-$40 or so.

When I tune the cap, the radio sounds average most of the cap range, then it suddenly changes and blocks out the station I'm trying to listen to. I'm guessing it's tuned to the station freq. :scratch2:

So what do I do to get the station I want if that's what it's doing?

If you tune the radio to a different station, does the "blocking" position of the loop tuning capacitor change, or does it turn out to be the same position? I am really grasping at straws here, but I am thinking that you might be tuning the loop to the IF frequency (455kHz) of the radio and setting up a feedback condition, that overloads the radio.
Another possibility is that the signal from the loop is exactly canceling the signal picked up by the internal loopstick of the radio... try rotating the radio or moving it away from the loop.

jr

Rotating doesn't change anything. Moving the radio away returns it to the previous signal as without the loop.

The loop shouldn't tune to 455k should it? Do I need to change the turns?

Rotating doesn't change anything. Moving the radio away returns it to the previous signal as without the loop.

The loop shouldn't tune to 455k should it? Do I need to change the turns?

Quite possibly it can tune that low... it is only about 100 kHz below the bottom end of the broadcast band...it is easy to miss the target frequency range by that much... I have removed and also added turns to loops that I have built to get the tuning range correct.:yes:
When you get this "blocking" effect, is the variable capacitor always tuned to near the maximum capacity (plates fully meshed)?
Are you aiming the loop correctly at the desired station? The axis of the loop points to the null, not the maximum signal, for this type of loop.

jr

Last night I tried changing the station, then the cap... seemed to work as it should... go up from say 780 to 790, then retune the cap just a bit and the new station comes in. Today I tried the same thing and it's back to the previous problem. I'm starting to think there's some frequency interfering from somewhere, maybe in the powerline?

So at least some of the time the loop seems to perform as it should.... perhaps there is a source of interference that is overloading the radio during the day...TV sets? computers? CF light bulbs?
Another possibility (not sure of your location) is that you might be close to a station like WTCM 580 kHz (which operates at 50KW during the day but only 1.1 KW at night)... The strong daytime lobe of this station is aimed NE from Traverse city. The 50 KW signal could cause problems at the low end of the broadcast band, if you are close.:scratch2:

http://www.fcc.gov/fcc-bin/amq?list=0&facid=70524

jr

We are sort of close to TC but about 60 mi south.

I'm going to have to try this outside away from the house next time it acts up.