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 > > -------------------------------------------------------------------- > ----------------------------------- _________________ Topband Reflector
