Brain dead. Manuals all in storage. Lowering the height of an antenna above ground, such as a beam, will cause the resonant freq to decrease, increase? Don W7WLL _____________________________________
Decrease. But not always -- I have a 10M beam at about 15 ft that goes up! The variable here is mutual coupling between elements and between elements and ground. Another error in using SWR as the ind
That's interesting Jim. I remember looking at a graph of the impedance change of a dipole at various heights. It doesn't like being very close to the ground, hihi. Don, FWIW, With my 2 el 40 meter be
Tuning an antenna close to the ground is a waste of time. You cannot predict what the SWR will be at your final height. John KK9A That's interesting Jim. I remember looking at a graph of the impedanc
Author: Dan Maguire via TowerTalk <towertalk@contesting.com>
Date: Fri, 27 May 2016 14:24:15 +0000 (UTC)
The "Resonate" button of the AutoEZ program makes short work of questions like this. For example, create a 20m dipole model with an arbitrary length of 33.5 ft at height "H" above ground. Set up a se
Decrease. But not always -- I have a 10M beam at about 15 ft that goes up! The variable here is mutual coupling between elements and between elements and ground. Another error in using SWR as the ind
Decrease. But not always -- I have a 10M beam at about 15 ft that goes up! The variable here is mutual coupling between elements and between elements and ground. Another error in using SWR as the ind
Resonance is where the reactive component of the feedpoint Z is zero. Lowest SWR could be at some point where the the impedance happens to work out closest. @@ Thats what I thought. Resonance = zero
What ever happened to the old method of standing it up vertical with the reflector closest to the ground ? Is that method out of favor now ?? 73, Dick, W1KSZ _________________________________________
Dick, I converted a 7 el 6mtr beam to a G0KSC LFA, reflector on a 13 ft flberglass ladder and tuned the DE. Worked very well. His loop fed arrays are so simple and easy to adjust I will not go back t
Yes the balun leads are part of the antenna. I have not ever modeled them and I typically have to shorten the DE a little. Is there an easy way to model these, it is such a short segment and the lead
Author: TexasRF--- via TowerTalk <towertalk@contesting.com>
Date: Fri, 27 May 2016 22:31:04 -0400
John, you could consider the two balun wires to be a balanced transmission line and model the effect of that. For example, if the wire spacing was 4 inches and the diameter was .1in the impedance wou
If you derive the expression for SWR in terms of antenna R and X you can differentiate with respect to frequency and determine the conditions for minimum SWR analytically. You'll find that when dX/df