Re: Ferrite antenna design in older portable radios


Rik
 

Were your widely spaced windings made with Litz?  I think wide spacing lowers self Cap. and so does using Litz.

It was awhile ago I looked at Online photos showing the winding on PL-450 and PL600 radio ferrite antennas. There was nothing remarkable I could see compared to other radios which are not especially directional. In my experience ferrite antennas are a bit more sharply directional than air core antennas which pick up off the open sides. Some pick up off the rounded edges which is sharper. Both my loops which do that are amplified, and at least one of the air wound Litz [wound on a removable 'peg'  form and sprayed to hold just the Litz wire together] designs I have picks up off the rounded edge, but I am not sure what that winding is called. That is too small for DXing.

I do have a 3 coil  contra wound with Litz form I use over a 2.125 X 16 inch stack of ferrite which is sharply directional for some unknown reason. I am working on a lighter more portable version, and plan to buy more lighter weight  toroids needed to get enough turns to reach my target uH range with this mix which is supposed to be higher Q at MW . Need a payday first.

-FARMERIK

There is mention of different windings and coverage in articles in the files of this group, which I have studied. On a fairly long ferrite rod, moving the coil from the center to either end cut the uH about in half. I am experimenting with ferrite just under each of three coils, and then varying the space between assemblies. Some changes are probably only measurable with test equipment, but optimal designs should be the best for DXing. One article mentioned increased Q when the ferrite was spaced under the center of the turns of Litz. There are many things to try.

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