80M INVERTED L "best design"

[F4EZJ]

Hi all,
i have some questions about inverted L project, for the moment i use one with 10m vertical part, and 10m horizontal part.

I want to know if i put more vert part like 15m VERT and 5m HOR, it will be better for DX i think so.

or maybe an other design will be the best one for DX. whynot!

and second questions is from the ground system, actually i use the same ground system with 1/4 wave 40m , is about 130 radials 10m long ,and i want to know if i put some other radials (20m long) for 80m will be better for L .
but what about for 40m result??? Maybe good for both

Thanks for answers
73's Steph

Ps sorry for my english!

grettings from F4EZJ Stephane

[W7LPN]

http://fraziersleeveddipoles.wetpain...ge/HF+Antennas

Like the article says I've built it over a metal roof & building. It "Works" well on the higher bands and passible on 80m. I have limited space, so it is a compromise of course.

[M0DSZ]

MMANA-GAL is a free software program which will tell you what you want to know. In the US, EZ-NEC is preferred because it's a home-grown product.
I find MMANA-GAL is easier to use however in spite of receiving EZ-NEC as a gift but EZ-NEC is probably more accurate.

[M0DSZ]

I've done a quick calculation for an inverted-L at 3.75MHz and the 15m vertical/5m horizontal is better. The gain equivalent to a dipole is at 22degrees and 32degrees elevation, it's slightly directional but the output is mostly vertical.

The 10m/10m version is similar in one direction at 32degrees but vertical in the other direction with a gain of about -3dBi at 22degrees elevation.
I assumed the lowest point of the antenna was at 1.5m and ignored the antenna impedance.

[KC4YLV]

I have run several L's for 80/75, the more vertical component you have the more it will act like a vertical, at 15m/5m its basically a 1/4 wave vertical with some top loading to resonate

losses decrease as you get elevation up, i have had OK luck with "L slopers" too. tie feedpoint to ground plane, throw rope over tree directly overhead and hoist antenna to that, then pull out remaining leg and get it as high and horizontal as you can. Most of your antenna current will be in the parts nearer the feedpoint so as long as you can get about 8, 10m vertical wire, it will work ok

[F4EZJ]

Ok Tnx for info, is just to know if it's better for DX to put more vert part or not, actually use 10vert and 10 hor and work very fine.

But maybe better with 15m+5m? is just my question


Merry Chrimas HNY 2009


Stéphane

[KC4YLV]

Yes, that's right. The more of the antenna you have vertical, the more it will have a low angle of radiation which is good for DX