Outdoor Antenna Performace Calcs
- Thread starter Whitehall
- Start date
No, its grounded to earth. You could mount an antenna to the flag pole, but not the pole itself.
Last edited:
RxDx
Speaker collector
If you're talking about Brian Beezley's site in post #1:
http://www.ham-radio.com/k6sti/
http://www.ham-radio.com/k6sti/
twiiii
Lunatic Member
I used Finney and Jerrold antennae back in the 60's and 70's. I still have a FM 10 Finney in the attic that I use now. The back lobe for the near bye FM towers and the front lobe for the FM station 80 miles away, It works while rejecting the Mexican stations across border which are way off to the side and more to the rear of the antennae.
k6sti
Active Member
Nearly all of my FM antenna models are for free space. This is fine for linearly polarized designs not close to ground. But circularly polarized designs at any height must be modeled over ground since ground permittivity and conductivity affect the azimuth pattern. For many years I have been using ground parameters for 1 MHz. Only recently did I realize how much they vary with frequency. Using 1 MHz values in the FM band compromises results so I've deleted several writeups and added a cautionary note to others.
To improve model accuracy, I've extracted generic 98 MHz ground parameter values from ground measurements made to 200 MHz by SRI International. While they are broad generalizations, they should be useful to anyone modeling FM antennas over ground.
HF ground parameters:
ham-radio.com
98 MHz ground parameters:
ham-radio.com
Antenna models:
ham-radio.com
Brian
To improve model accuracy, I've extracted generic 98 MHz ground parameter values from ground measurements made to 200 MHz by SRI International. While they are broad generalizations, they should be useful to anyone modeling FM antennas over ground.
HF ground parameters:
HF Ground Parameters
98 MHz ground parameters:
Antenna Notes
Antenna models:
88–108 MHz
Brian
k6sti
Active Member
I've updated my tilted dipole writeup with 98 MHz ground parameters:
ham-radio.com
I discovered this antenna by accident on my computer. I had no idea enhanced reception of circularly polarized signals was possible with a linearly polarized antenna. Within a few minutes I had hung a folded dipole from my ceiling fan to verify that tilting it increased signal strength. It did, and noticeably so. I was a little surprised because I'm on a hilltop where flat earth simulations do not fully account for the complex ground reflections I experience. The stations I noticed improvement on were 21 miles away and not line of sight. Another complication not modeled. The tilting trick is so simple that I think you should give it a try with any indoor antenna.
Above 8 feet or so, the tilted dipole advantage over a horizontal or vertical dipole drops off. Note that raising any antenna always increases signal strength. It's just that the benefit of tilting it lessens with greater height. If you live above the ground floor, it's still worth trying because terrain irregularities or local reflections may alter incoming polarization. Tilting an antenna best matches your antenna polarization to that of the signal.
Brian
Elliptically Polarized Tilted Dipole
I discovered this antenna by accident on my computer. I had no idea enhanced reception of circularly polarized signals was possible with a linearly polarized antenna. Within a few minutes I had hung a folded dipole from my ceiling fan to verify that tilting it increased signal strength. It did, and noticeably so. I was a little surprised because I'm on a hilltop where flat earth simulations do not fully account for the complex ground reflections I experience. The stations I noticed improvement on were 21 miles away and not line of sight. Another complication not modeled. The tilting trick is so simple that I think you should give it a try with any indoor antenna.
Above 8 feet or so, the tilted dipole advantage over a horizontal or vertical dipole drops off. Note that raising any antenna always increases signal strength. It's just that the benefit of tilting it lessens with greater height. If you live above the ground floor, it's still worth trying because terrain irregularities or local reflections may alter incoming polarization. Tilting an antenna best matches your antenna polarization to that of the signal.
Brian