8. HF GP with looped radial

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8.
HF GP
Looped Radial

7.
18 MHz
Delta Loop

6.
18 MHz
Delta Zepp

5.
Ladder line fed
HF GP

4.
Ladder lin fed
HF horizonntal wire ANT

3.
14/18/21 MHz
Vertical ANT

2.
Old HF ANT remake

1.
Old HF ANT

B1 HF antennas

8.
Multi-band HF GP Antenna with Looped Radial

Awesome!
Looped Radial / Self-balancing Function

The left is a part of JH1GNU / Kobayashi OM's presentation at the "Ham Festival 2023" in Tokyo. English version can be checked at his QRZ.com page here .

Astounding presentation in a sense; saying;
Looped radial has a self-balancing function

GP antenna at my place
I had used a GP antenna at 8m-high feedpoint, consisting of 5m vertical element and two 5m horizontal radials (1.0mm dia. copper wire loosely wound around FRP fishing pole).

BTW, as I get older, anything large becomes annoying, probably because of my getting weaker in mental perception with the advancing age (I was born in 1944, amid air raids). A bulky car parked at my place gets me uncomfortable. I became to like a compact, yet good handling car.

The same looks true to ham radio antennas. I became to like a simple and smaller antenna with reasonable performances. As HF antennas and "neighbor' eyes" inherently do not get along well, smaller antennas are favoralbe in this respect too.

Yet another digression; these remind me of a passage of Sei Shounagon's essay, "The Pillow Book" ^#1, written just 1,000 years ago, saying "anything, anything, things small are all beautiful".

Under the circumstances, I use a GP antenna. Yet the 5m + 5m radials at 8m high looked awkward. If placed at 20m high, it might look OK though. So I shortened the fishing poles to 2.5m + 2.5 m, and pulled back the remaing 2.5m wires inwards. Still all worked as before. Below is the overall sketch.

The GP was fed by a 300-ohm ribbon feeder with a manual tuner. It enabled me to work on the 7 bands from 3.5 to 24 MHz.

In the past, I used self-built ladder line. This too I felt awkward. First of all, it was too much for my max. 100W operation. So I took the ribbon feeder for its easy routing.

As its loss in the rain is said larger than the ladder line, I let the feeder go inside the VP13 PVC water pipe. This also works to keep the tuner adjustment in rainy days same as that of fine weather.

The only issue was a strange feedback to the shack on the 7 MHz band. PC's two LCD screens repeated off and on with the 60W or so CW keyings.

I suspected that the cause was the unbalanced currents of the right and left radials, because of the following reasoning.

Mechanically the right and left radials are symmetrical. However, electro-magnetically, not so. Because the radial position is too low, and the interaction with the surrouding objects gets larger.

The reality must have been that in the 40m band, the particular environment at my place happened to be unfortunate, i.e., the electro-magnetic symmetry was largely distorted, and in the other bands, though looked good, they were merely less unfortunate, i.e., the asymmetry were comparably less.

And I left the 7MHz problem as it was, because, in multiband operations, it was certain that I would end up in the situation of an old saying here, "If you please this one, you will displease the other".

Then I encountered the above Kobayshi OM's description, reporting, unbelievable to me though, that the looped radial has an inherent current balancing function!!

REALLY??!!
Well, his meticulous measurements and reasonings are indeed convincing. I could not help but making the long hesitated modification.

Looping the radials
As the radial ends already bent inwards, the modification was very simple, just to connect the radial ends together as in the follwoing sketch.

The modification result was remarkable! The 7MHz problem has disappeared completely, and the tuning works on all bands became more stable than before.

This, I understand that the intended monopole operation realized, by the balanced radial currents which cancelled out each other and eliminated the horizontal detrimental radiation, and only the vertical plane radiation remained intact.

Finally my antenna has become the GP antenna in its true sense.

Great thanks
This is like, someone's chronic disorder long given up its remedy is gone all at once by the advice of a renowned doctor.

I am deeply grateful to Kobayashi OM.

Note #1: "The Pillow Book"
please see here .