[Antennas] Antenna Feedline Question

Mon Sep 6 16:11:37 EDT 2004

Paul said:
> Not sure what you mean about the antenna, what is the total physical
length
> of the antenna, and what is the length of the feedline? What kind of
tuner do
> you have? What kind of balun are you using?
> Paul, K5AF

Paul, OM:
The 40/20/15/10M dipole is made with 450 Ohm ladderline, fed with 450 Ohm
ladderline. Each half of the dipole is made from one piece of ladderline.
The two wires of the ladderline in each half of the dipole are connected
together at the feedpoint. One wire in each half is 36' 1.5" long for 40
and 15M resonance, and has a 7' 8" stub made with the ladderline, connected
3 feet from the end, to give 3/4 wavelength resonance on 10M. The second
ladderline wire from the feedpoint is 18' 9" long to give 20M resonance.
The feedline is 45 feet long. The balun is homemade 1:1 balanced to
unbalanced. Resonance is about 7.1, 14.1, 18.5 (damn!) and 28.2 Mc. swr is
1.1 to 1.3. As noted, when I added 30 feet more feedline everything went to
Hell.
The WARC dipole is similar with the long wire 22' 8" and the short wire 12'
11" (each half). Feedline is 41 feet 450 Ohm.
The feedline lengths were fortuous. I may have trimmed the antennas to work
with the connected feedlines!
The tuners (tried with longer feedline) were a MFJ-949C, which may not be
good for high impedance balanced matching, and I tried a National MB-150
multiband tuner which should be fine for high Z. All in all, they work fine
without a tuner for the original feedline length.
Richard