Rob, Unfortunately you wont be sure! The MFJ meter only compares the magnitude of the current in the two wires; crucially it doesn't look at the phase. So when the meter indicates "balanced" any one
Be aware that those "additional line loss due to standing waves" curves are approximations. There are cases where a particular combination of line length and load cause the loss to be LESS with a hig
Tim, Some "rough and ready" EZNEC modelling suggests you need 40-45uH depending on the diameter of the vertical - I assumed the top was #14 wire. Rrad is about 19 ohms. 73, Steve G3TXQ ______________
Dave, I was shooting for 1.9MHz. 2" diameter gave me 40uH and #14 wire gave me 45uH. Steve G3TXQ _______________________________________________ _______________________________________________ TowerT
Tom, Modelling that in EZNEC over average ground I see little difference in the main lobe, but some change in the small high-angle lobes. Best result of the various current combinations I tried was w
Antenna efficiency (as opposed to antenna system efficiency) has little to do with resonance, but a lot to do with its radiation resistance relative to its loss resistances. A resonant dipole with a
Martin, Just one point of detail. If you construct a folded dipole of wire which has a low(ish) differential-mode characteristic impedance, and which has a significant difference between its differen
Martin, I agree - it's a good way of explaining how the impedance transformation arises. But it's important to realise that, even when you're not using zip cord, the currents in the two wires are NOT
Jim, Quite so! In the measurements and modelling I've done on folded dipoles, nearly all the VSWR bandwidth enhancement (around 97% of it) can be attributed to the "fatter" conductor; the contributio
Roger, Well said - surely we're not now dependant on the Internet to do multiplication for us !!!! I had to check the date to make sure it wasn't April 1st. Converting cm to inches is easy - multiply
I'm not sure I would use the same language as Jim, but I *do* think there is widespread misunderstanding amongst Hams about the performance of "ladderline". There seems to be an ill-informed presumpt
Dan, Amen to that !!! Steve G3TXQ _______________________________________________ _______________________________________________ TowerTalk mailing list TowerTalk@contesting.com http://lists.contesti
Rick, A very interesting topic! When I try modelling a helical vertical in EZNEC (zero wire loss) and then compare it with the same length straight vertical (zero wire loss) I do see a slightly incre
It models fine for me: 120ft vertical radiator Bottom "capacity hat" 8ft off ground, 4 x 20ft horizontal wires + 4 perimeter wires Two top loading wires at 45 degrees, each 28ft long. All wires #14 c
Jerry, I apologise - I misunderstood which set of dimensions you had a problem with. For what it's worth, the N6LF QEX dimensions model OK, John's 80m dimensions model OK, but I can't get close with
Dan, My model had a 1ft straight wire at the base, with 10ft of helical above it. I used 240 turns - couldn't do more without running out of EZNEC segments. The source was right at the bottom of the
One way of achieving lots of top "capacity loading" is to stick a remotely tuned mobile whip on the top of the vertical. When it's below resonance it's capacitive and variable. In the 1970s a local h
Barrie, It's a compact 2-element parasitic beam and performs like one. It has some attributes which I like: * 5 bands with a single coax feedline * Small turn radius * Easy to build yourself * Light-
When you are doing the coax loss calculations, don't just assume a matched load. I don't know what antennas you will have at the end of the run, but is it possible they might have a VSWR of 1.5:1 or
Of course, the trap doesn't have to be resonant in-band. In fact trap losses are highest when the trap is resonant at the operating frequency. 73, Steve G3TXQ ________________________________________