Topband: Spitfire question

[Peter Voelpel]

Hi Eduardo,

I will contact my friend Andre, DF9OX, to find out more about his tuning
process.

http://www.df9ox.com/e_afu80mtxant_spitfire.html

73
Peter

-----Original Message-----
From: Topband [mailto:topband-bounces at contesting.com] On Behalf Of Eduardo
Araujo
Sent: Dienstag, 5. November 2013 14:49
To: Topband
Subject: Re: Topband: Spitfire question

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 at 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
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Topband Reflector