Hi Jim,
Have you tried measuring the current in the parasitic when connected?
73, Greg, ZL3IX
On 2013-06-07 09:29 a.m., Jim Brown wrote:
I'm building a simple 2-el vertical array for 40M, with one element
driven against radials, and a passive reflector with an equal number
of radials. NEC predicts 2.7 dBi over lousy ground at 15 degrees,
with peak gain of 3.6 dBi at 25 degrees elevation, and F/B of about 8 dB.
We've got this set up in W6GJB's pasture, roughly 5 miles S of me,
with me centered on the main lobe, and I'm looking signal strength
with my K3 reading relative dB (and with AGC turned off). Our signal
is 35 dB above the noise level with Glen's KX3 at 3 watts. Terrain is
hilly between us, and we have 16 radials on both elements.
We're making three measurements -- with the array as designed, with
the reflector shortened by 3 ft (which should make it director) but
still connected to the radials, and with the reflector simply
insulated from the radial plate.
What I hope to see if the antenna has the predicted directivity is 3
dB difference between the designed array and the reflector floating,
and 6-8 dB difference between the array as designed and reversed.
What I see instead is the same signal strength for all three
configurations within 0.2 dB. So the question is, why? A vertical
plot in NEC shows the F/B at all elevation angles, all the way down to
1 degree and up to 80 degrees.
73, Jim K9YC
All good topband ops know how to put up a beverage at night.
_________________
Topband Reflector
All good topband ops know how to put up a beverage at night.
_________________
Topband Reflector
