The Inverted Vertical

[KL7JV]

I had a strange idea last year to build a 1/4 wave vertical for the 160 meter band inverted. By inverted I'm talking about the traditional 1/4 wave vertical antenna with a four spoke perpendicular 1/4 +20% wave ground plane stood on its head. The tip of the vertical is now at ground level and the ground plan at about 80 feet. In this arrangement I believed it could achieve a lower take off angle but I'm not real sure about ground losses. I do think its possible that I am losing power heating the dirt in my yard to achieve the low angle. Maybe adding a ground plane to the antenna along the gound would help reduce this effect.

Im curious with what the antenna modeling programs would do with this arrangment.

Any ideas?

[KY5U]

Leave the ground radials buried, just feed the vertical at the top.

[AG3Y]

Now 5U, how do suppose that to work ? Have you actually tried it ? How do you isolate the feedline? How do you hook up the "ground" of the feedline when it is a quarter wavelength up in the air? etc etc etc ? ? ?

You give no answers, but you sure DO open up a lot of questions!

"Inquiring minds want to KNOW ! "

[AI3V]

Google Discone,

Now google "Inverted Discone"

It will work fb.

Rege

[KI4TWB]

A few months ago, I fed my 30 foot antenna support into the tuner as the antenna and used the off-center fed dipole as the ground. Seemed to work pretty ok, at least I could pick up quite a few signals. Didn't do any transmitting, though.

Boredom and beer can be a lethal combination!

[AG3Y]

AI3V, a "discone" is in no way, shape, or form, an "inverted vertical" in the same manner as the OP suggests. One of the major problems would be constructing an antenna in that fashion and at that wavelength. Now I have seen discones, notably at a nearby airport that appear to be large enough to extend into the upper HF bands. But how to erect a discone large enough to be efficient on 160 meters is beyond my comprehension!

Furthermore, what would be gained by doing so? A discone's main attribute is its frequency agility, not its gain as compared to a resonant single band antenna, such as a 1/4 wave vertical.

Oh, and BTW, JV, where did you get the dimension of "around 80 feet". The vertical element would be closer to 136 feet ! Quite a difference !

73, Jim

[KL7AJ]

I had a strange idea last year to build a 1/4 wave vertical for the 160 meter band inverted. By inverted I'm talking about the traditional 1/4 wave vertical antenna with a four spoke perpendicular 1/4 +20% wave ground plane stood on its head. The tip of the vertical is now at ground level and the ground plan at about 80 feet. In this arrangement I believed it could achieve a lower take off angle but I'm not real sure about ground losses. I do think its possible that I am losing power heating the dirt in my yard to achieve the low angle. Maybe adding a ground plane to the antenna along the gound would help reduce this effect.

Im curious with what the antenna modeling programs would do with this arrangment.

Any ideas?

Greetings. Back in the mid 70's...(That's 1970s!) I worked for a comm compnany that had 74 MHz call boxes all over the city. They had an inverted coaxial dipole atop each one....supposedly had a slightly lower angle of radiation than a "proper" coaxial dipole. They worked fine.

The only disadvantage of your idea is that you don't get to claim it's original.



eric

[KL7AJ]

AI3V, a "discone" is in no way, shape, or form, an "inverted vertical" in the same manner as the OP suggests. One of the major problems would be constructing an antenna in that fashion and at that wavelength. Now I have seen discones, notably at a nearby airport that appear to be large enough to extend into the upper HF bands. But how to erect a discone large enough to be efficient on 160 meters is beyond my comprehension!

Furthermore, what would be gained by doing so? A discone's main attribute is its frequency agility, not its gain as compared to a resonant single band antenna, such as a 1/4 wave vertical.

Oh, and BTW, JV, where did you get the dimension of "around 80 feet". The vertical element would be closer to 136 feet ! Quite a difference !

73, Jim

Y;

The logistics problems go away if you feed the coax up through the vertical tubing. Actually the Titan Gap sort of does this....in a somewhat lame fashion.

A lot of experiemntal work on inverted antennas was done in the broadcast industry in the late 70s as well. One notable antenna, the Prestholdt array toyed with this. Alas, the "zero skywave" Marconi never fully materialized...but the effectiveness of upside down verticals of many forms was pretty well proven.

Eric

[AG3Y]

Eric, another difference between the OP's antenna idea, and your company's coaxial dipole ( otherwise known as a "sleeve dipole" ) is that the feedpoint is in the center of the antenna, and both sides ( the vertical radiating element, AND the sleeve covering the feedline ) of the antenna are fed from the center. There is no "ground plane" with this sort of antenna, any more than there is a "ground plane" with a half-wave dipole mounted a fair distance above the ground. ( or in the hypothetical "free space" configuration ) Nor are there any "radials" that the OP advocates. The sleeve antenna is in reality, just another half wave dipole, with physical properties of being able to isolate a quarter wavelength of the feedline from the radiating portions of the antenna.

73, Jim

p.s. remember the Isotron(tm) antennas for VHF/UHF bands? Basically just a sleeve dipole with a flared cone instead of a cylinder ! And some of us thought that it was a "BRAND NEW" idea !

[KB3PXZ]

If you invert you a verticle won't your voice sound like it's be played backwards on the receiving end ???