GE Eddie, Felipe, some direct mailers and all,
seems, the spitfire array got some interests, I got also some direct mailed
questions.
I will try to answer, and try to remember my tuning way 2003 - 2006.
Just found some, maybe 20, Din A4 handscribed papers, from tuning procedure
2006;
but need to remember some details not wrote down :-)
Also I need to update my homepage; newest HAM-radio details are 6 years old,
there
changed a lot.
At first, description of my array and anything around:
- center tower is 27m high, grounded. Fired by gamma-match for 80 and 160m.
Caps are
now Variabel VACs for GU84 power (homepage not updated)
- Radials: Using ~120 radials, between 10m and 30m long. Additional buried 4 x
(10mx0.6m)
chickenwire. During Winter 4 to 6 times chickenwire 10m to 25m long. Around
centre tower
16m² chicken wire
- Unused elements of the array are grounded via 3mm Cu and the radial net.
- Array Wires had been ( shortly destroyed by a storm :-( ) 1mm copper with
steel inside.
- QTH is relativly flat and empty, only to SW over W to NW there are less
buildings. Trees
and bushes are not very high or far away the other directions.
http://www.df9ox.com/e_afu_rxants_bev.html
- ground seems to be very conductive, QTH here near a main german river, Elbe
(4km).
Groundwater in summer 1,4m, winter 0,7m deep. For my beverages transfering -12V
via
ground is no problem.
My array seems to be working ok (80m)
I can see up to 25dB f/b, up to 35db f/s.
Gain is up to <6dB.
But often it is also much lower, depending on elevation angles and conditions.
All compared to the single center tower.
When using the single center, everything else is grounded.
Reference *1: I will use some abbreviations (W1,W2,W3) down, this is the file:
http://www.df9ox.com/docs/Spitfire%20Dimensions%20(other%20bands).JPG
Reference *2 for the array description is:
http://www.df9ox.com/docs/FVR%20Spitfire.ppt
@PY1NB
No, I do not have any files for NEC.
Maybe John W1FV or Fred K1VR as the authors can help out.
All I find around 2007 in internet I mirrored on my homepage.
ON4UN described the spitfire in chapter 3.7.4, I think he modelled it with NEC.
@LU2DKT
Hello Eddie
I did it the same way, tuned it for maximum f/b, but used no caps at the
corners, changed the
length.
Especially changed W3 (reflector only), w1 and w2 (director and reflector).
I followed *2, page 8 and 9. Thatswhy I gone only for f/b, because gain should
be ok in that
small QRG area, while gain area is much broader.
Starting point was good f/b on 3650kHz with the aim of 3510kHz.
So I need to make something longer.
> 1 - Did you just adjust both elements in one direction for max f/b ?
> or gain ?
1. Started with the reflector part, W3, later I made some tests with the
director part W1-W2.
Always changed all 4 directions in the same way, but tried to find some
differences between
the 4 directions in the evening. But this did not happen here, changes were
equal.
Was looking for good f/b.
> 2 - Did you start with the dimensions given by the authors and then
> change it a
> little bit at a time ? both of them or just one of them and then the
> other? in which
> direction adding or shortening
2. Yes, started with the given dimensions.
Changed it typically in 0.1m steps; if I saw a result like "0.1m makes 15kHz",
changes like
0.2m or more were done.
At first only reflector part, W1, later I made some tests with the director
part W1-W2.
If I saw I was above 3510kHz with best f/b, increasing; otherwise decreasing.
> 3 - Do you have notes about how much your element length differ from
> the
> original design? could you share those numbers?
3. Yes, I ended with W1-W2, director, 0.3m longer (W1 26.9m => 27.2m),
reflector part W3 1.1m longer (W3 3.5m =>4.6m).
> 4 - Did you measure element resonance after you antenna was working?
> how
> did you measure? (in order to repeat it in here)
4. Yes, I did a lot measurement with my MFJ 259 at the corners (W1 W2), also
after finished
tuning.
But I am not sure with my handscribed papers at this point with exact
F-resonance
versus dimension of W1, W2 and W3.
> 5 - Finally, how do you achieve omnidirectional radiation? did you
> just open at
> the corners or ground each element?
5. Grounding all elements
> 6 - If you ground it, how do you do that? a ground pipe o connect it
> to the vertical
> radial system?
6. Unused elements are grounded via 3mm Cu down the post and connected to the
radial
net.
Eddie, don´t know whether that will help you.
For my understand of the array you still found that best gain point if you are
in the maximum
peak of f/b.
You measured 1dB gain at 0° elevation angle, thats ok, maximum gain is >20°
elevation.
You did yet not seen any noticeable effects on signals from EU and PY.
Maybe because of still no flat angle conditions?
I see many times also less gain, but f/b is good.
Other days there is really good gain, and less f/b.
And another day there is less f/b and no gain.
Depends all on conditions, incoming angles.
I would like to see there is a point which gives you an idea for improving
something.
vy 73 de André DF9OX
>
> Hello André, I really appreciate you took the time for sharing your
> experience.
>
> I used for tuning the last procedure indicated by the authors, which
> was to use a
> reference signal from the back (700 mts in my case) vertical
> polarized and adjust
> both reflector and director back and forth for maximum f/b (using
> variable
> capacitors inserted at the corners) which should give you also max
> gain across
> the range.
>
> Well....... f/b was good, more than 20db across 25Kc but I only got
> 1db gain
> maximum.
>
> I understand you did it using a practical way but, I still don´t
> understand how you
> did it, because changing dimensions every day and waiting for
> results could give
> millions o possible changes and difficult to decide which direction
> to follow.....add
> or cut the reflector? add or cut the director at the same time .
>
> Could you please be more specific ? or as specific as you can so I
> can repeat
> your procedure?
>
> 1 - Did you just adjust both elements in one direction for max f/b ?
> or gain ?
>
> 2 - Did you start with the dimensions given by the authors and then
> change it a
> little bit at a time ? both of them or just one of them and then the
> other? in which
> direction adding or shortening
>
> 3 - Do you have notes about how much your element length differ from
> the
> original design? could you share those numbers?
>
> 4 - Did you measure element resonance after you antenna was working?
> how
> did you measure? (in order to repeat it in here)
>
> 5 - Finally, how do you achieve omnidirectional radiation? did you
> just open at
> the corners or ground each element?
>
> 6 - If you ground it, how do you do that? a ground pipe o connect it
> to the vertical
> radial system?
>
> In my case I am using almost 120 radials 1/4 wave long for the 1/4
> wave vertical.
>
> I definetly need a help to make it work. I am only interested in
> gain because I
> have other receiving antennas.
>
> Many thanks in advance for your time,
>
> Eddie, LU2DKT
>
> --------------------------------------------------------------------
> -----------------------------------
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Topband Reflector
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