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[email protected] · April 4th 14, 07:38 PM posted to rec.radio.amateur.antenna

wrote:
On Friday, April 4, 2014 12:26:30 PM UTC-5, wrote:

A 5/8 system mounted at 13 feet (top of an average house) will have a

squarish pattern with a maximum of 4.4 dBi and a minimum of 2.2 dBi.

A 1/4 system at the same height has a circular pattern of 4.9 dBi.

In both cases the major elevation lobe is at 20 degrees.

Free space patterns can look wonderfull, but unless you live on the ISS

your antenna is going to be mounted over ground.

True, but all mine have been at 36-40 feet up, so the numbers
change a bit.
When I modeled them all, I used a height of 40 ft, and "avg" ground
if I remember right.

At 40 ft, the 1/4 GP with sloping radials gave a max 3.003 dbi at 9 degrees.

The 1/2 wave gave a max 3.831 dbi at 8 degrees.

The 5/8 with straight 1/4 radials, 4.293 dbi at 39 degrees.. Not good.

The 5/8 with 45 degree sloping 5/8 radials, 4.941 dbi at 8 degrees.

The same with even steeper sloping radials, 5.334 dbi at 9 degrees.

Yes, height makes a HUGE difference which is why when quoting numbers it
is important to state the height.

--
Jim Pennino