Peter and Tom
I really appreciate your feedback and let me ask you
for a little help with this if possible.
Tower or driven element is a quarter wave with 120 quarter wave radial.
The 2 element hang from the top of the tower in opposite directions to an
anchor point 40 mts from the base but suspended at that point at 3 mts from the
ground and keep that hight returning to the tower as the final anchor point.
I followed (I think) the tunning procedure suggested by the authors which
consisted in keeping the driven element connected and using a vertical
polarized signal from the back (700 mts in my case) tune the reflector to max
attenuation, then the director for max attenuation and iterate both until
maximum attenuation from the back is reached. That procedure is suppose to give
a f/b centered in your chosen fcy (thats is what I got, more than 20db across
25Kc) and max gain >3db from 1800 to almost 1900.
In the original article an according to the modeling program reflector ended
tuned to 1900 and director to 2000 so I was not so far away following the same
procedure (always measured with everything connected). That procedure was
suggested because it is supposed to be easier to tune for max f/b than for max
gain.
I am really NOT interested in f/b but in forward gain. (I have other receiving
antennas)
Could any of you suggest a different tuning procedure? unfortunately I don´t
have knowledge on modeling tools yet. I Would highly appreciate that. Could it
be to do the same procedure but for max fwd gain?
Many thanks in advance for your time.... Eddie,LU2DKT
On Monday, November 4, 2013 10:57 PM, Eduardo Araujo <er_araujo@yahoo.com>
wrote:
Hello Dear Topbanders,
I had the chance to test the Spitfire
antenna during the CQWWSSB.
I installed it to cover initially one direction.
I had no problem to tune the elements to 1840 using a source signal from the
back. Reflector ended at 1855 and
director 2050, both tuned to max attenuation to the back as suggested by
designers.
At first I was delighted because I got f/b at ground level of more than 20db
across 25 Kc but surprise came when I
could not notice any improvement in the front gain switching on/off the
elements to medium distances (Brazil) or long
distance like Europe where it was pointed to (and same line of Brazil).
I measured FS at 300 mts at ground level and I only detect 1db maximun change
Reading ON4UN book, It looks like because of its configuration, the main lobe
is shifted upward a bit, so I could
think that because of that I measured very little at ground level but not
noticing any detectable change at
Brazil (3000Km) nor Europe (>10000Km) it really makes me wonder if it is
working at all.
Before changing the project to other direction, I would like to hear your
opinion and or suggestions.
Many thanks in advance.... Eddie, LU2DKT
_________________
Topband Reflector
_________________
Topband Reflector
|