How to Build a Flat AM Loop Antenna

Dave's Homemade Loop Antennas

AM Loop Antenna - Very Effective - DIY

Am loop antenna plans

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Welcome of my homemade loop antenna or loop aerial pages. All the loops described here were designed and built by myself. The features are not real different from loop to loop. These loops are made to enhance radio reception in the broadcast, or medium wave MW band range.

Some of the loops are just one coil, am loop antenna plans, some have tuning capacitors and some have an extra coupling coil. Read on and discover the fantasy of loop antennas. Or fetish in my case. All these loops am loop antenna plans a resonant tuned circuit made up by a multi-turn loop coil and a variable capacitor. If you are using one of my designs shown on these pages, you are all set to am loop antenna plans ahead. But if you are designing your own loop antenna, please read on.

As just mentioned, a resonant circuit is made with the coil and variable capacitor. These numbers are fine when using a small diameter coil, but are grossly inaccurate with a loop antenna coil. This inaccuracy is due to a relatively large amount of self capacitance also called distributed capacitance built in to large diameter wire coils. The tuning range is determined by the ratio of minimum capacitance to the maximum capacitance. As an example, the ratio of a pF variable capacitor is But if you have 20pF of self capacitance of the coil, then the effective value of the capacitor is pF or a ratio of just over There are a couple of ways to tune the whole band.

One is to add a fixed capacitor and a switch which places an additional pF or so capacitance in parallel with am loop antenna plans existing variable capacitor. Another fix is to use a higher value variable capacitor which will restore am loop antenna plans higher ratio maximum to minimum capacitance values, am loop antenna plans.

Knowing this information saves the new builder from an unpleasant surprise and the necessity for a redesign. Now on to my loop projects . Here it is friends. I made a loop specifically for one radio. This my loop 6.

I was using my "test" am loop antenna plans which is shown below to see how my Sparton radio would perform. I decided that this antenna had to be lightened up a little. I cut a notch in both pieces of wood so that they would interlock.

The pieces are glued and fastened with a single flat head wood screw. The wire is wound with some litz wire. This makes a nice looking wiring job when finished. You will need 70 feet of wire for the tuning coil and about 14 feet for the outer coil.

I thread the wire for my loops outside where there is room to pull the wire. The drilling and other details are contained in the drawing shown below. I used litz wire between the loop terminals and the base box, am loop antenna plans.

Earlier I had used 18 gauge PVC covered wire. This was too stiff and the loop would not stay in the position it was turned to. Just one of those little learning things. All the parts could be mounted on the loop itself, am loop antenna plans, or a small board could hold the loop with a small panel for the other parts.

But I like those basswood boxes that I have. The Sparton radio is a multi band set and the shortwave bands require a different antenna. I added a switch and some terminals to accommodate this need. The radio antenna is switched between the loop coupling coil, or an external antenna and ground. The other switch is a high low band switch and adds a pf capacitor across the pf variable capacitor. A larger value of variable capacitor would tune the whole band in one chunk.

This loop is not real expensive to build, but they require a lot of building time. Use your imagination and you will be as proud of your loop as I am of mine. This is my 4th loop. Sorry for leaving 2 and 3 off the site, but those were so much like my first that I decided I would wait for something worthwhile to offer. I wanted a loop with lots of bells and recovery from cancer surgery and chemo to do my radio experiments, am loop antenna plans.

Look at what this loop has to offer, am loop antenna plans. This loop has two windings. The larger winding 15 turns is connected to a variable capacitor for a large tuned circuit. Since a single pf capacitor will not tune the entire broadcast band, more capacitance has to be added, am loop antenna plans. I am using a ganged capacitor and a switch.

Included is a third position of having no capacitor across the coil. I did this as some of my radios tune the antenna loop by a ganged capacitor inside the radio, am loop antenna plans. The other winding 2 turns is to connect to the antenna input of the old BC radio. I picked two turns as that emulates the single turn that my dad had on his larger loop. This loop has 3 wood pieces. This is a little larger than my earlier loops so that I would have room for that extra winding.

After the holes are drilled, I stained the oak with Minwax Red Mahogany stain. Thin wood, plastic or anything you have around will work. Before you mount everything, am loop antenna plans, fit it together and take a look to see if it looks right.

Another change from my first loop is how the ends of the wires are handled. This makes 2 extra holes I had to drill. What the heck, holes am loop antenna plans cheap so I splurged.

The wire can be then looped around a couple of times. This holds the ends secure and looks neat too. On the top of the mast pole am loop antenna plans each side arm, I drilled 17 holes. Then measuring down from the top of the pole 25 inches, I drilled a series of 21 holes going back up the pole, 15 holes, one for each turn, one for the end winding.

Then two extra holes close spaced for ending the tuned winding, am loop antenna plans. When the wire is wound on this loop, it will look like a square. Three more holes are drilled for the untuned winding. I think that comes out to Good thing I stayed awake in the first grade! You with me so far? This is the weak point of the loop. If the loop falls over the dowel will break and need replacing.

Next I built the box that serves as a base for the loop and holds the capacitor. Using that big thick 14 gauge wire, I make the connections to the capacitor and link switch. In my case, I used a 3 gang capacitor. That made it easy to use a single link switch to do what I wanted it to. You could make two spst link switches, one to add a fixed or second gang and the other to disconnect the capacitor from the circuit.

I built mine the way I wanted, and you can build yours any way that is handy for you. C onnect a radio to the untuned 2 turn loop and tune the main coil with the capacitor. H ook an antenna and ground to the two turns and a diode and earphone on the tuned side for a cool crystal set. Or if I was really close am loop antenna plans the station, forget the antenna and ground.

U se the untuned winding as a tickler coil in a regenerative set. U se only the large loop without the tuning to connect am loop antenna plans a radio.

This loop could be used to replace a built-in loop on a radio. C onnect the coupling loop between a wire antenna and a crystal set for a wave trap. Make sure the loop is turned to null the station you want to trap. Maybe I could use this loop to strain my spaghetti. Anyway, below are some pictures of how I constructed the loop. If something is unclear or you have a better idea on something, please e-mail me.

These loops are very cheap to build but take a long time to make. But they sure look cool sitting on top of your old radio. Best of luck with yours!

 

Am loop antenna plans

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