On Nov 7, 2:08 pm, "Richard Fry" wrote:
wrote On 160m, many think they can elevate a vertical 20
ft or so, and use maybe 4-8-10 radials to get good
performance. It just doesn't work that way. At such a
low height in WL, they need almost as many as a ground
mount.
__________
You may be interested in the paper linked below, which reaches
a very different conclusion, verified by field experience.
NEC models of this system in the broadcast band with the radials elevated 20
feet show gains equal to those using a classic broadcast buried radial
ground system. And if this true in the broadcast band, I expect it is true
for 160 meters.
http://www.nottltd.com/ElevatedRadialSystem.pdf
RF
The only problem is I see no direct comparisons to a normal set
of buried radials. Only that they were able to meet the "minimums"
required by the FCC. I would be curious to see how well the 6 radial
setup would compare to a non crippled set of 120 radials.
It's interesting, and I'd already seen it, but I'm not really
convinced
thats it's equal to 120 radials in the ground.
Certainly usable though..
I've seen plenty of tests done by amateurs that pretty much swings
in the other direction. In fact, being my 40m GP was on a
push up mast, I was able to try it with it's four radials, but at
lesser heights. It did not work near as well at 1/8 WL, vs it's
normal 1/4 WL height. And in terms of wavelengths off the ground,
it had an advantage over the 160m scenario.
Also, modeling might show them equal, but that still doesn't really
convince me until I see it happen in the real world.
I've seen a lot of hams have very mediocre results doing pretty much
the same thing on 160 and 80. I remember one in particular that
got fed up and replace it with a set of normal radials on the ground.
Greatly improved his performance.
I guess I'm a firm believer in the loss per number of radials vs WL
I often quote... :/
So far, I've never seen any indication they are off by any great
degree.
BTW, I still prefer the elevated vs ground mount. I'm just not as
optimistic about the number of radials required to equal 120 in the
ground as they are. :/
MK