Resonance or Lowest SWR (
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- เผยแพร่เมื่อ 17 ก.พ. 2023
- Chris, KB1NLW, is wondering if the antenna will have the highest efficiency if tuned for the resonance and if low SWR can be achieved through a tuner. Watch to learn more.
#antennas #SWR #Resonance
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Glad to see someone show that resonance and low SWR are not the same thing!
We have gotten kind of lazy now with all our antennas designed for a 50 ohm feedpoint impedance and 50 ohm coax. Open an ARRL Antenna Handbook from pre-1960 and you'll find LOTS of great antennas that are fed with open wire feedline (450-600 ohm or even more!) End fed antennas that don't use a balun to match impedance, but a specific length of feedline as a matching network! Once this concept of resonance is understood there is a whole new world of antennas to make!
It is the audience, including myself, Dave is teaching. More advanced antenna design is always freely available to those who seek it.
Perhaps this may add some clarity: To a great extent, power reflected from a mismatched load is not dissipated in its source, it is re-reflected from the source. Some reflected power is dissipated in the transmission line, and some is eventually dissipated in the load. An L/C network used to achieve a conjugate match (i.e., antenna tuner) at the load or at the source will dissipated some power, depending on the Q of the components utilized. If the network is between the transmission line terminus and the load, it appears as the load to the transmission line. If the network is between the source and transmission line, it appears as the load to the source, and as the source to the transmission line. With the network at the source, any mismatched load and associated line losses remain; but maximum power will be supplied by the source due to the matched load condition achieved by the network at the source. Ken WA8FCI
Yes, the best answer to the question.
Dave would look into this I believe 👍
De VU2RZA
Good video...73!
Maybe this explains the tuning of a magnetic loop antenna?? You first tune for peak noise and then tune for lowest SWR. When looking at a waterfall display with an expanded span, the peak noise often becomes off-center of the frequency you are on when you tune for lowest SWR.... If this is true, is tuning for lowest SWR really that important if it is not excessively high?
Dave hi
Question. I hv an end fed 6-80(142 feet)Running an icom 7300 and I would like to get on a small bit of 160. Even in emergency mode, I cannot tune it. EM does tune the 3.92-4.00 portion of 80, which my internal tuner will not. Anyhow, would an external tuner like an Mfj-939 be able to hit a bit of 160?
Thanks
William
Excellent explanation !
Didn't we see this one already? Or was it part of another topic in the past?
A DX Commander is the answer. Dave has some video's on how to assemble it.
Well of course! There is a DX before the word Commander, so you know it is an antenna specifically designed for distant contacts ;)
Dave, it is obvious that you became nervous as you have not done just to the question...hi..
De VU2RZA
An SWR of 1:1.5 seems like unachievable for me.. oh well
I trim or tune antenna for the bands using, to get it close, and let the antenna tuner do its thing to make the radio happy.
I never understood the use of an antenna tuner, why not tune the antenna in the normal fashion by properly cutting the antenna to length per a mathematical equasion for the frequency???
Because you would need a different antenna for every band you wanted to transmit on. And wide bands like 10M would need more than one antenna. And yes I know you can use traps, but they themselves introduce losses.
Great video! Exactly what I have tested and vetted out very recently on some new antennas. Perfect lesson!
There are many antenna types that required a trans-match.
@@charleswoods2996 The ARRL antenna book has other options beyond tuners. Sometimes it's difficult for "some people" like Charles Woods to look beyond themselves. Just sayin'.