High-Efficiency, No-Radial, Inverted L for the 80m Band

[R. Fry SWL]

Readers here might be interested in some form of the 80m, inverted L antenna system concept outlined in the graphic below — which needs/uses NO radials of any kind, might fit on a small lot, has high radiation efficiency, and useful radiation patterns.

73,

Richard Fry (W9XMT)

[WA4WAX]

Here is how it was done back in '59.

You can voltage feed a nominal half wave without radials, but I have not seen that done with 1/4 wave. Of course, you can voltage feed the same wire on the higher bands.

In the article, he is running it as a Marconi on 80 meters.

https://worldradiohistory.com/Archive-Radio-News/50s/Radio-News-1959-01.pdf

[K9MB]

Just curious how you know this antenna is efficient?

A lot of work has been done on this and the rub is that you can couple energy out into the antenna system and make it look like it is working, but a lot of the energy goes to warm earthworms and little gets radiated  unless you happen to be at sea and have lowered a cable deep in that conductive pool below you.

The reason radials are there is to shield the antenna fields from lossy ground.

The only efficient way around this, I understand is to use a tuned counterpoise, which unlike radials- is resonant.
K2AV did a lot of work with folded counterpoise antennas.
CEBIK was a genius in this area. I have a link to his inverted L article below
They only work well, however, if one uses an isolation transformer to make sure the antenna only sees the counterpoise and the earth is in the shadows where it cannot suck up rf energy.
No free lunches served, I think.
I am open to instruction however if you have discovered something new.

In my youth, I spent a lot of time with wheels and magnets trying to achieve  perpetual motion, but it always coasted to a stop and that was without removing any energy… Anything can appear to work if you ignore enough inconvenient facts…😉 73, Mike

PS: Note- an inverted L is essentially a quarter wave vertical with the top bent over. MB

https://k2av.com/Olinger_NCJ_article_on_FCP.pdf

http://vtenn.com/Blog/wp-content/uploads/2016/12/Inverted-L-Cebik.pdf

https://www.m0mcx.co.uk/wp-content/uploads/How-many-radials-do-I-need-for-a-vertical-antenna.pdf

http://www.astrosurf.com/luxorion/Radio/qex-ground-systems-part-4.pdf


https://www.n1fd.org/2019/10/23/radials-vertical-antennas/

[K4RT]

Are you actually using this antenna without anything as a counterpoise? What type of feedline are you using with it? I would think that as shown without at least some sort of counterpoise you would have high impedance and high reactance issues and resulting effects.

[R. Fry SWL]

Just curious how you know this antenna is efficient? ... I am open to instruction however if you have discovered something new. ...

________________

Because while it may not be widely recognized or accepted, Physics tells us so.

The short paper below provides some details.

[WD8BIL]

Efficiency will depend on ground conductivity, to a great extent. Some ground is worse than others. This is why radials are needed.....I say again....  NEEDED... for any vertical quarter wave.

[R. Fry SWL]

Efficiency will depend on ground conductivity, to a great extent. Some ground is worse than others. This is why radials are needed.....I say again....  NEEDED... for any vertical quarter wave.

__________

However the _radiation efficiency_ of a transmit antenna system itself is NOT affected by the propagation losses affecting its radiated waves after a radius of several wavelengths from the system radiation center, to propagate along a lossy ground plane, and/or in free space.

[W1ITT]

Richard..
It's not clear to me from looking at the diagram in your first post how this antenna is fed.  Is the loading inductance above the 1.4 meter wire stub, with a series coaxial feed above that?  Or is there a tapped feed across part of the inductance?  Please 'splain that detail more closely.  In any event, I'm guessing that it would be necessary to choke the outer of a coaxial feed to keep it from trying to be part of the antenna itself.
73 de Norm W1ITT

[K9MB]

Just curious how you know this antenna is efficient? ... I am open to instruction however if you have discovered something new. ...

________________

Because while it may not be widely recognized or accepted, Physics tells us so.

The short paper below provides some details.

Thanks- this paper says almost exactly what I said.
The premise-apparently- because this is evidently one page of a more complete paper- that ground losses are very significant-if and when the ground is the missing half of the radiating element.

The reason that radials are put down is to shield the radiator from the ground and it is notable that radial fields are not resonant- they are just a faraday shield to keep the antenna from “seeing” the lossy ground.

The writer in his last statement refers to the superiority of an elevated ground system being superior to just connecting to a ground rod because of the losses.

What is not stated is that this elevated ground must either be a copy of a large radial field, or a resonant counterpoise.
I posted a link to K2AV work on folded resonant counterpoises and he has had good results with that.
However- I will reiterate- the elevated ground counterpoise will not work inless the entire antenna is fed using an isolation transformer, which renders the ground below opaque to the antenna. If you just put an elevated wire up and call it “elevated ground, it will be transparent to the radiator, which will now see the lossy ground and it was useless.
By the way- I took several years of physics and math. One must consider all factors when solving a problem or it will introduce errors, like in this case.
Maybe you can share the entire article. It does look interesting…
73,Mike

[R. Fry SWL]

Richard.. It's not clear to me from looking at the diagram in your first post how this antenna is fed.

____________

The loading coil is placed at the bottom of the longer (upper), discrete section of the vertical conductor.  One conductor of the feedline is attached to the coil input; the other conductor is attached to the top of the short section of the vertical conductor.

This feed configuration is not all that novel or mysterious.  It is used in OCF dipoles, "EFHW" antenna systems etc.

[R. Fry SWL]

... The writer in his last statement refers to the superiority of an elevated ground system being superior to just connecting to a ground rod because of the losses.
____________

That is a misunderstanding of what I posted.

The reason for the improved efficiency of the elevated configuration I posted is: there are no lossy, high ESR paths in it to convert the r-f current generated by the transmitter into heat.

[K9MB]

... The writer in his last statement refers to the superiority of an elevated ground system being superior to just connecting to a ground rod because of the losses.
____________

That is a misunderstanding of what I posted.

The reason for the improved efficiency of the elevated configuration I posted is: there are no lossy, high ESR paths in it to convert the r-f current generated by the transmitter into heat.

I am puzzled by what you mean by “high ESR paths?
“ESR” means equivalent series resistance, but it sounds more technical. I have mostly seen it in components like capacitors because it affects the Q of the devices.
In this case, it is merely the resistance of the dirt and rock under your antenna.

None of this is of any use, however, and the elevated ground idea is useless, also to eliminate that “ESR” path, unless you render that lossy ground as opaque to the radiating element.
Again- you must not only elevate a ground screen plane, or tuned counterpoise (they are not the same), but you need to isolate the elevated ground or counterpoise from your feed line shield, which will connect you back to your “ESR” (lossy ground).

Failure to do that will render the process useless. You may still be able to get a signal out- it does not take much at HF for basic communications, since QRP is popular, but you can ditch all assertions about “high efficiency”.
73, MB

[ki4nr]

In my experience End Fed anything is crap. I have myself & friends tried these type of antennas and they are inferior to a Inverted Vee or flat top dipole up high. Never mind the RF problems in the shack because of no ground radials, Even with minimum ground radials you still have RF issues.

Your far better off if you have postage stamp lot, to put up an inverted vee with apex high as possible and configure the wire in whatever way you can to get it on your lot. No Ground radials to deal with & way better signal and no RF as long as you have a coax choke at the feed point. You can't beat the dipole antennas way up high on the low bands.

[R. Fry SWL]

... the elevated ground idea is useless ...

__________

The configuration of the elevated antenna system I posted neither HAS nor NEEDS an elevated ground, or any other kind of ground to have high radiation efficiency.

In its basic form, it is an off-center-fed dipole antenna with the longer arm of it bent at a 90° angle along its length.  Both arms radiate.  Neither arm is at "ground" (Earth) potential.

[K9MB]

... the elevated ground idea is useless ...

__________

The configuration of the elevated antenna system I posted neither HAS nor NEEDS an elevated ground, or any other kind of ground to have high radiation efficiency.

In its basic form, it is an off-center-fed dipole antenna with the longer arm of it bent at a 90° angle along its length.  Both arms radiate.  Neither arm is at "ground" (Earth) potential.

Oh- ok. You are right- it is not an inverted L, but an inverted Vee with one side vertical and one side mostly horizontal.
That- as you say- needs no ground, though it likely needs an isolation choke (“balun”) to prevent a hot common mode current on the coax shield.

It does remain unclear why one would not just would not just put up a low inverted vee and bend the ends to fit your lot.
I suspect it will be a cloud heater anyhow, but fine for local and short hop.
A half wave sloper might be possible too.

You could also call it anything you like, as in the great Fleetwood Mac song- Go your own way… Call it thunder! 😉 73, MB

[WA4WAX]

If you can go up 45 or 50 feet, a voltage fed T becomes an option.  OK, 55 might be a little better.

The horizontal wire could be as short as 88 feet.  Voltage feed at the bottom of the vertical wire.  That will put the high current region well up in the air.

Idea: USE OWL line to the horizontal wire.  That way you have a good Hertzian antenna will balanced feed for 40 and down.  ON 80, bond the two OWL wires together, and the line becomes your vertical radiator.

Use a series-parallel link coupled circuit.  Consider a Faraday shield for the series tuned link (Reduce noise), and ground the parallel LC circuit via a 2.5 mH choke.

Have fun.

[WA4WAX]

In this situation, the horizontal wire acts as the counterpoise when you run it as a vertical.

[WB6NVH]

The VSWR curve looks scary on the specs.  I defer to the experts but it looks like already over 4:1 at the edges of the modulation sidebands on either side of the carrier (center.)