All, I have a questions regarding calculating ground impedance. How can this be measured?? The impedance of a loaded vertical measures about 50 ohms, however model programs predict the antenna impeda
Hi, Dan; Can your measure the real and reactive components of the impedance? When you say 'loaded vertical,' I'm guessing you imply a vertical element shorter than 1/4 wavelength and the real compone
Yes and no... First off, impedance is complex (it has both a real (resistance) and imaginary (reactance) part). A loaded antenna is using a reactive component to "counteract" the reactive component
I think you are asking about ground resistance, rather than impedance. Measuring ground resistance can be very difficult unless you know every other variable involved, including everything about the
Tom, Thank you for your reply. Yes, ground resistance. This antenna is a custom 'screwdriver'. The base is about 4 inch diameter 1/8 inch wall aluminum tubing. The coil is wound on a 3.5 inch form of
Radiation resistance formulas are at: http://www.w8ji.com/radiation_resistance.htm The coil loss can be pretty high on low bands in a screwdriver antenna, but the ground loss is the real killer. It
Tom Rauch wrote: I have a questions regarding calculating ground impedance. How can this be measured?? I think you are asking about ground resistance, rather than impedance. Measuring ground resistan
It definitely isn't easy. It is all but impossible for a ham to measure the radiation resistance, ground loss resistance, and antenna loss resistances. Even broadcast stations are forced to back the
Tom, I am trying to increase the efficiency of a center loaded vertical by creating a good ground system. Based on models the antenna 'should' have a have a total impedance of less then 10 Ohms. Yet
If you study the replies that you have been given (and you have been given some very good ones), it all boils down to this: 1) Assuming that you are measuring the impedance correctly at the feedpoint
Dan, Maybe or maybe not. 50 ohms is very high since any lossless shortened antenna would have less feed resistance than a 1/4wl antenna...and that's about 30 ohms or so. So you probably have somethi
Even Sevik was fooled by this. He thought we could measure earth resistance at low frequencies (power line frequencies) and extrapolate that data to HF conductivity. The method even made it into Han
resistance HF anything what George Hagn (formerly at SRI) did a lot of work on measuring actual ground parameters at RF, using a open two wire transmission line. He actually started using dipoles (f
Jim, I'm not saying they don't exist, but I have not yet found a coil modeling program that agrees with direct measurements of large RF inductors. Is there a link to that free program? One program to
Some years ago, Jack Belrose, VE2CV suggested that one of the better ways to approximate ground characteristics at a given frequency would be to erect a precisely measured low dipole just high enough
real This was the approach that George Hagn started with. He was looking at propagation and antenna designs in SouthEast Asia, especially for field expedient antennas (i.e. no multi element beams on
I would guess that's a worthwhile thing to include as long as your radials are in the same position as the test antenna. Once they are in a different position (height, direction, etc) all bets are o
At 09:02 AM 4/13/04, Tom Rauch wrote: This is just a bunch of wasted discussion because it would be much faster and more accurate to measure what you want to know........field strength. There is litt
frequencies, the I don't know that it's particularly difficult to get measurements to a few percent. Tedious, perhaps, but not requiring any real special equipment. A standard antenna impedance analy
Hope this doesn't cause too much laughter but I keep thinking of that graph in the Ant Handbook which shows dipole Z vs height. Could you put up a modelled dipole at a known height, measure its Zin a