Home |
Search |
Today's Posts |
#1
|
|||
|
|||
Trimmed Van Gorden All Bander - suprise!
I'm just getting setteled into a new QTH and funds
are tight so instead of buying a tuner to tune my Van Gorden "All Bander", I decided to see if I could trim it to resonance on 40m. For those who don't know, the All Bander is a ladder line fed 134' dipole. It comes with 100' of ladder line but I didn't need nearly that much so I trimmed the ladder line to 50'. At that point I have a 12 turn, 5-1/4" dia coax choke then 20' of RG58 going to my SWR meter. As a 134' dipole, the antenna presented a good swr at 5, 20 & 28 mhz. I wanted 40m so I started trimming. By the time I was done I had shortened the antenna by about 25 feet per side. I'm not sure exactly how much (+/- 1 ft) I trimmed but I was VERY carefull to keep the antenna even sided. The antenna now presents a good SWR centered at 7.151 mhz but it also is OK at 18-19.5 and 26.5-28.5! Sweet! Performance seems good, too (or maybe condx are good now)... The antenna is setup as a dipole with apex & ends at about 17' AGL. It runs facing 290 & 110 degrees. One end ends up in a tree, the apex up on my roof and the other end via nylon twine to a telephone pole. What I don't get is if I shortened it, why did the 20 mhz low swr point move *down* 1 mhz while the 5 mhz point went up to 7.151 and the 28 mhz point went down 1/2 mhz? I'm happy with the results as I now (with a seperate dipole for 20m) have my 4 favorite bands: 40, 20, 17 & 10. Anyone care to offer a theory as to what's going on with this setup? 73's de Ken KG0WX |