[TowerTalk] Fw: elevated radials vertical

[EC1CT Fernando]

> Sounds like the good old ground plane covered in most Antenna literature.
> Most ground planes have 4 quarter wave radials either horizontal or 
> sloping
> away from the antenna base.
>
> Dave K4JRB
>

Talking about these things. Yesterday, I was setting up my new top-loaded 
quarter wave vertical for 80 meters (see me at qrz.com). It´s made by EA5JK 
and the loading system is pretty similar to those used at GAP verticals. I 
got a huge metallic roof (galvanized steel, about 2000 sq/ft. not so far 
from the shack) so in company with a fellow hams we installed the vertical 
up in  the roof and attached directly to it. Using a MFJ analyzer we found 
out that the antenna tunned correctly buy we got a very low impedance (about 
20 ohmns) so we assumed that the performance wasn´t as expected. Tried a 
couple of quarter wave radials that didn´t have any effect on the antenna 
(not on SWR neither on impedance...strange, isn´t it?). We decided to take 
the antenna down and mounting at ground level. Installed the 2 quarter wave 
verticals (on of them elevated) and we got the perfect 1.1 with an impedance 
close to 35 ohmns and an efficiency of  99% (acording to the antenna 
analyzer). After this, we connected the coax to the radio to make a side by 
side comparision against my half wave dipole for 80 at 33 ft. The 
propagation wasn´t quite good so I didn´t have any reply from outside of 
Europe. Comparision?...well the dipole beated the vertical in about 2 S 
units every time. In those cases when the signal got over 9, I had a 59+10 
on the vertical and 59+20 on the dipole. The only advantage I have seen is 
that the vertical is less noisy than the dipole. OTOH I´m still trying to 
figure out how the hell the vertical doesn´t work out over the metallic 
roof. It could be that we got so much ground plane?....Wondering if 
isulating the antenna from the metallic roof and adding a bunch or radials 
would let it work out. It would be a perfect location far from the 
neighbour´s view...Any suggestions?. 73s all
EC1CT Fernando
E-mail: ec1ct at ure.es