EFHW counterpoise test
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- Опубликовано: 27 авг 2024
- 5/14/18... After many test I have concluded that both of these wires should be grounded. The transformer works best when located near earth with a short ground lead to a simple rod plus it provides some lightning protection. See my later videos.
Testing the EFHW with ground, without ground and with counterpoise. No difference is found. Secondary ground wire can be left floating. However you do loose lightning protection. The test proves that there is no difference in performance between using a ground, coax shield or counterpoise.
This test was also conducted in a different manner by Myantennas. Disconnecting the secondary ground had no effect on shield radiation. • EFHW test
Thanks Steve! Quite interesting. I do agree by grounding that lead it keeps the Antenba at D.C. ground also prevents electrical static from building up..
Looks like it is connected in series
I have constructed several efhw transformers, I use one at home in an inverted L for 40-10m and a couple for portable. My results also confirm no counterpoise is needed, but what I do get is the swr increasing if I move the coax away from vertically straight down, so pull the coax say 45 degrees from the transformer and the swr will jump from 1.1 to 2.0 easily. This shows the coax shield is working as the counterpoise and certainly interacts with the antenna. 73s Carl M0CLS.
Carl. You are correct and after much experimentation I made this video. ruclips.net/video/MzfQybYMlUc/видео.html
That's helpful. Thank you. KW4PW
Excellent test findings.
Thanks Steve
Would it be possible to show EXACTLY how the capacitors are attached. It looks like there are at least two different ways to do it. Thanks.
When you refer to no effect SWR is now a direct measure of actual radiated power, to my understanding. I have even read higher SWR on an EFHW. An actually be more efficient.
Interesting results. Now the test to make, doing the same test as you just did, would be to put the MFJ-854 current meter on the coax and check to see if the RF on the outside of the shield goes away after adding a counterpoise ? I don't expect that to change by just adding a DC ground connection.
Barry, KU3X
A counterpoise turns the antenna into an off center fed doublet. The ground does more than you think when it comes to these high impedances. It doesn't take much!
Does the 0.05 wavelength counterpoise prevent RF near the operator with a half wave or slightly short "halfwave" antenna?
You don't need a counterpoise. The coax shield does that job. Also it's good to ground the coax at the transformer. Nothing fancy...Just a ground rod. Nobody I know has reported excessive RF in the shack with this design but it must be 1/2 wavelength on the fundamental frequency....Not "sightly short".
Thanks for the video. I have experienced the old saying, ask 25 Hams and you'll get 26 opinions on this subject. Some very adamant. You said the caps combined were 100uf, everything I read says to use 100pf. I wonder if that was just a slip up.
I see the replay to another comment, 100pf, great thanks.
I said pico farads. pikeo not micro