Begining 2003 I asked myself, whether there is not a bit more possible for my backyard, 45x40m, than a simple vertical.
Those well known 120 times x-m long radials were planned, end of 2003 layed, 2500m.
After opening a threat in Topband-reflector, the 4-square was realized
as not a good idea; place is not enough for its necessary radial-system.
Other ideas were sloper, Delta-loops etc...
And also the unknown Spitfire I finally decided to build.
Delta-loops I used before, Slopers had been to vague for me; also other ideas.
The Spitfire is a kind of vertical polarized 3el-Yagi.
A central lambda/4 (or similar) Vertical is used as radiator, 2 folded full-size elements as director and reflector.
There are very less Information available in net about the Spitfire.
The system was first published by K1VR and W1FV (who informed me on that system) for 160m at Dayton 1998.
There are a PowerPoint-Presentation, an FAQ and a 2001 distributed list for other bands.
I have mirrored them on my site: PPT, FAQ and list
Please, for better understanding the concept and my experience,
read first above documents!
For more information please move the cursor over the pictures
HISTORY OF MY SPITFIRE:
First attempt 2003:
On top of a 21m high vertical 3mm thick Cu-ropes were installed, and I
used original length from the above list.
Woodden supports had been set in early fall.
But now it was late November and no time for dry tuning with MFJ259B.
This attempt was a "nil".
In CQWWDXCW 2003 I saw some effects, but no really gain or f/b.
In addition, the first relais burned at test begin friday night.
The heavy Cu-ropes were lengthen daily, later hanging in guy-wires.
January 2004 a storm did the rest. 15m of the Vertical were kept alive.
No Pro for the Spitfire.
Second attempt 2005:
This year my Vertical was totally redesigned: 26.5m tall and rolls for the Spitfire at 21m; for comfortable lengthen the Spitfire director wires at Tower-level, 11,5m.
But, this time my Spitfire wire was to thin, 0.6mm.
It was lengthen also from day to day.
Again it was late November, and no dry time for measuring with the MFJ259B.
Those used original length gave me a maximum at abt 3.350 MHz, tested with commercial signals.
Many changings of reflector length brought me less results...
Some time later first 0,6mm Cu-wire cracked, not long later
the other 3.
Another season without extra-gain. But the lonely 26.5m Vertical was very fine.
Third attempt 2006:
I am stiil in learning processes. This year it is early September; rainy August is gone.
Wire is DX-wire, Copper with steel core, 0.95mm thick.
Again length tuning is possible via those rolls in 21m high.
Reliable good weather... I tuned every length according to the description. Unused elements were layed on ground, disconnected.
Tower is misstuned to 2.8 MHz.
Not bad, it lasted long, but thanks nice weather and MFJ it runs great.
Until first praxis-test: ZERO effect on 3510!
After some beers:
I measured again, and gain and f/b are ok, but on 3630.
What a hell... ok, "some" lengthen of the director and reflector-elements without MFJ are bringing the result between 3500 and 3560.
Btw., reflector-part is now again nearly original length. Director 1m+/- shorter.
Between 3500 and 3560 some dB gain on dx, and 20dB f/b, average.
Peaks are abt 9dB gain and noise reduction 40dB.
Offcourse it depends on incoming angle, azimuth and elevation.
Much more interesting. Many more dx is audible now.
CW-dx at the edge means every dB rules.
Switching between lonely vertical and Spitfire sometimes said, 229 or 559 as given report.
In fact, there are no 3 S-units difference, but it means (you CW-guys know) a QSO is possible or not.
"There is no free lunch"....
much more than feelable gain and reduction to side and back.
Feeling really like a 3el. Yagi.
My 2el. Delta loop array back in 1998 was really unefficient compared to now.
A really difficult to tune Antenna. You need a lot time!
60KHz bandwith with that gain and f/b looks like a lucky combination of director and reflector lengths.
Theory says something narrower.
- Relais: Finder relais are not ok, burned 3 of 8. Not switched hot.
- Wire: Not to thin/thick, sag will come. Use copper with steelcore.
- Guywires for elements: take care for UV-resistible ones.
- Length of elements: take care for sag! 20 cm are critical! Also u will very easy loose some 10cm in relais-boxes.
- Corner: those 20.54m for CW spacing are on my opinion not enough.
- Relais-boxes: take care, UV-reliable they have to be.
- Grounding of unused elements: ok via (underground) connection to the hopefully great radial-net.
I have some...
If fall will go on like these days (2006-09-27), news here next weeks.
-11.5m Aluminium Tower 70x70cm
- 4,5m Steelpipe 60mm/5mm diameter/wall
- 5,0m Aluminiumpipe 50mm/2mm diameter/wall
- 3,0m Aluminiumpipe 45mm/2mm diameter/wall
- 2,5m Aluminiumpipe 15mm/1mm diameter/wall
(pipes are overlapping; written length are except overlapping areas)
Gamma-match consists of 7 Cu-ropes, each 3mm diameter,
in parallel to Alu-Tower. (Outer 2 are for 160m)
Tap-point is 11.5m high, distance between ropes and tower 60cm, distance between ropes 10cm.
Cap is abt 220pF, voltage 5KV; no probs even with some power.
System is bright. In worst case, even SSB is possible (SWR 2.8, no Spitfire gain there. Vertical lonely)
Coax: 2m 1/2" HCF, 25m 7/8" LCF underground, 10m RG213
My homemade rig-control-box is not only for the spitfire, and will
hopefully be ok for next years wishes.
Built it with moduls inside. Also labels, switches etc. are easy to change. So it will be not basically unusable if I switch my mind...
Until now only some parts of the box are activated.
The Spitfire control switches gives me for testing purposes not only
the 3el. option, but also some other possibilities for switching.
E.g. "dd s rr" means "2 directors/radiator/2 reflectors"
Whether there are some useful combinations will show the future.
2006-09-25: I am running in moment only the single Vertical!
Burned more relais; so waiting for ordered vacuum-switches.
2006-11-10: Russian switches "B1B" are well working (see pic
on the right). They are specified for 3KV and 10A, and are
running without probs a month now. But, they need real 24V,
better more. Otherwise there is the possibility for not correct
switching through. (also visible Finder relais are only needed for
my given box switching logistic)