Antenna Tuners: Impedance and Feedline SWR - Two Experiments (076a)
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- Опубликовано: 9 фев 2025
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NOTE: I make some comments herein about where the reflected power ends up. These are going to be refactored in the next video where I address the issue more directly.
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Antenna Tuners or Antenna Matching Networks ... they are ubiquitous in the Amateur Radio World. They used to be things that hams either built for themselves or bought as a separate unit to include in the shack. Now they are very often included in transceivers.
This video is an adjunct to the previous two videos that I created on the subject of antenna tuners.
In this video I will perform two experiments to demonstrate two aspects of what they do. These are related to specific aspects of what they do after they are fully tuned to provide the lowest SWR for the transmitter:
1. Impedance at the Antenna connection
2. Feedline SWR.
The next video will address the topic of the reflected power in the feedline and its associated SWR.
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Time Markers for Your Convenience
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00:05 Introductory Comments
01:35 Experiment #1-Impedance
01:35 Introduction and Setup
02:16 Performing the Experiment
05:11 Experiment #2: Feedline SWR
05:11 Introduction and Setup
05:57 Performing the Experiment
09:06 Final Comments and Tootle-Oots
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Thank you for a very informative video. I had a big smile on my face at the 6:34 time mark when the SWR = 3.16 : 1 Take care Rick
I guess I'm not the only one, eh? 🙂
This was another fantastic video! I'm very interested in your next one! Keep up the great work. ~ 73 ~ AC7WH
Thank you so much! 🙂
Well explained! Thanks a lot Ralph.
Thanks! And, the next video is going to be really revealing, too! Where does reflected power come from and where does it go. I'm studying deeply for that one even just now. 🙂
Measure the tuner backwards, why didn’t I think of that! Thanks for challenging my assumptions of what was going on at the other end of the impedance match. Looking forward to the next video.
Thanks! 🙂
Thank you Ralph. Can't wait to see the next video. 73 OM
You are welcome! 🙂
nice demonstration, i had to rewind it many times to understand it somewhat. a block diagram of the whole setup would have been very useful. thanks
Thank you! ... and you are welcome! 🙂
"Never sees the antenna", I can't wait for the comments on that!
Yup ... but the next video answers that question. 🙂
A certain coffee drinking youtube channel needs to see this. Their criteria for a good matching unit is one that matches a 10:1 vswr. They claim such wide matching is good for portable low power operation
True that! The truth is that reflected power is lost power. It never sees the light of day. This is what I will show in the next video. The first, and most important, part of the amateur radio station is a well matched antenna. Get this as good as you can get it, then think about the rest of the gear. 🙂
@eie_for_you
Is Maxwell wrong stating reflected power is either radiated by antenna or lost in the feedline
@@Pioneer936 Quoting from the book "Practical Impedance Matching" by Ain Rehman, page 23, "Mismatch loss in transmission line theory is the amount of power expressed in decibels that will **NOT BE AVAILABLE** at the output due to impedance mismatches and reflections." (emphasis, his) He goes on to provide the equation for this entity. As I will demonstrate in the next video, this power which he says is totally lost to the output is the same as the reflected power in the feedline. On this basis, I say that the reflected power due to impedance discontinuities does not add to the power delivered to the antenna. 🙂
@@eie_for_you that would go against what maxwell states
Walter Maxwell, book "Reflections" says the opposite, that reflected power is re-reflected again by the matching network.@@eie_for_you
Excellent video. May I suggest that it might be improved by a few diagrams though; based on the old adage that a picture is worth a thousand words.
Unfortunately, YT does not allow me to update an existing video. I can totally delete it a video and upload a brand new video, but I cannot update an existing one.
I will most certainly keep this in mind for the next video which will sport two experiments as well. 🙂
@@eie_for_you Sir, I know this. My comment is/was meant to be gently constructive criticism and I hope it is taken as such. Whilst I enjoyed your video I found it difficult to follow you without repeated pauses to give me time to sketch out your setups.
Regards
Dave
@@daveturner5305 Aaaah! A lot of folks don't know that about RUclips, so when questions come up like this, I like to be sure they understand the dynamics that I have to deal with as a content creator.
Your comment was received as nothing more than constructive criticism which, as I indicated in my reply, was received and will be taken into account in future videos.
Thank you for the suggestions. Always looking for ways to "improve my serve." 🙂
The term 'antenna tuner' is a misnomer as they do not tune antennas., they only match to it. Great video!
@se2702 maybe they called tuner because they tune the antenna system to resonance
Hi Ralph,
Would have made more sense way back to call it an antenna matching unit (AMU) rather than an antenna tuning unit (ATU). That one letter conveys the actual use of the circuit. An ATU is much more suited to being sited at the antenna. Thanks for these videos. Stay safe. 73 WJ3U
I cannot agree with you more! You are very welcome! 🙂
Or antenna coupler
@@U812-k7j yup
@DonDegidio not necessarily have you read reflections by walt maxwell
@@Pioneer936 I am in the process of reading the "Another Look at Reflections" by Walter Maxwell right now. It is *totally* fascinating ... I *LOVE* it. It ALL makes perfect sense. While I was convinced by the other story line because of some of those who we supposed authorities preaching it, I was never completely satisfied with it. There were too many things that just didn't quite add up.
I ordered a used copy of the actual book (a collector's edition was >$240!, I didn't go for that one. I took the "dinted" version for $24). 🙂
Yup. You match the transmitter, where the tuner is... so put the tuner at the antenna end... and then there won't be very much loss, because of reflected power, due to mismatch. However the antenna has to radiate the power... and so... if it is not efficient ... then, there is still losses.
Match != no losses.
Proof: dummy load
@@mrtechie6810 Okay. Use better coax. And a dummy load, is often used to temporarily replace the radiation resistance of the antenna; but, is not equivalent to it... especially in any real antenna.
Match = no reflected power to the transmitter.
Yes, there are losses in the antenna tuner ... this is the nature of real world components.
Match = there is still reflected power as seen in the feedline; you saw this in this video. Yes, feedline loss is an issue, but this is not the same as the power loss due to reflected power. These are two entirely separate issues.
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I am refactoring my reply because of new information that I have come to understand. This will be reflected in the next video.
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@eie_for_you surely the tuner placed at the antenna feedpoint negates the losses otherwise seen in the feedline with the tuner placed at the transmitter?
@ Be careful now ... feedline loss is one thing. It is a function only of the feedline itself and is a function of frequency irrespective of the SWR of the antenna or the reflected power that accompanies it. You can see this expressed in dB/some distance on the transmission line (e.g. coax) datasheet in the table by frequency.
The antenna matching network (antenna tuner) does not (as you saw in the video) eliminate the power reflected from the antenna due to the impedance mismatch between the antenna and the feedline (as short as this may be). I do not think it is reasonably possible to locate the matching network right at the antenna feed point without some length of feed line/transmission line. If the connecting feedline does not have exactly the same impedance as the antenna, then there will be power reflected at that connection point. I will demonstrate this effect in the next video coming out on the 19th. 🙂