The PHILCO Phorum
Two Turn Counterphase Loop - Printable Version

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Two Turn Counterphase Loop - RGK20m3 - 10-13-2025

Built one, 20x22”, 2” between loops- installed on a pivot inside the cabinet of my 38-7 that allows maybe 30 degrees movement in each direction. Very impressive performance and the pivot allows a good measure of noise cancellation, although maybe not as much gain as the tuned loop that I built previously.
   
Interesting phenomenon is that the placement of the power cord is extremely critical; from totally unlistenable over most of the dial, to the exact opposite- absence of any noise. It seems that if the cord is vertical in line with the pivot that it is quiet.
Ground screw is attached to the grounding cavity of the wall outlet as no ground rod is practical and no metal piping here.
Anyone have any experiences like that? Not my build, but what I based mine off of.

RE: Two Turn Counterphase Loop - Chas - 10-14-2025

As an experience exactly as yours with a Philco and homemade loop, no.

But, the phenomena your experiencing has more to do with a long path of the power safety ground to earth. Such a ground is not immune to RF noise and in fact is often, the bypassing of other equipment in terms of noise. Keep in mind further, the power ground is not a "one way street" like a water drain.

Consider removing the chassis or any other such bonding to the service "U" ground. Reduce the value of any "Y" type power bpassis in the chassis to .001mf.

Use a RF filter at the outlet but its effect may not be great as there is no short direct earth ground.

Keep the power cord at right angles to the loop.

Consider design of a shielded loop and moving the radio where a short ground can be used.

I, had to move my favorite radio from its place to my left hand on a sofa table. RF noise has come to my address since a home explosion some 500 feet away. I suspect there is chemical smoke damage or loose electrical fastener on the 7kv service.

I, placed the radio next to a homemade ACME loop that is attached to a modified Zenith 53. Such mod provided for an external loop as well as a long wire. The Zenith is not powered but its RF tuning is available to tune the ACME loop passively. That greatly increased the desired signal and cancelled some 90% of the noise.

When the storm damage is abated from recent weather I will contact the power company to address the noise. Yes, though it took some time for Eversource to respond, they did address a noise issue on a lightning arrestor some 6 years ago.

Chas

RE: Two Turn Counterphase Loop - radiorich - 10-14-2025

Hello RGK20,
Well I like the design I have General Electric Tabletop model J-64 that is missing it's original tuned Antenna that is part of the tuning circuit and there no value on the schematic .

Sincerely Richard

RE: Two Turn Counterphase Loop - RGK20m3 - 10-14-2025

I have thought about trying a counterpoise around the perimeter of the room for a ground; interesting idea about reducing the value of the line caps.
Right now the performance is pretty good, or I should say as good as anything I have tried. May experiment some more….