Video: Oscilloscope Balanced Antenna System Tuner Performance Test

I agree 100% and there could be a generational difference, most people are nearly 70 plus years old I speak to, I am in my 30's so, there is a stylistic difference I think as well. Remember this is just a hobby, a rather unknown one these days...

 

This is really a very effort consuming task, first you would have to check each part of the system independently, the ant at the feed point, feed-line its self and transmatch.
Symmetrical tuners are less suspect and placing the Balun on the input does not guarantee that it’s forcing equal current into the line. The ground reference of the system parts also matters, if any... so yes anything is possible.

 

I think so. One leg of my doublet runs adjacent to a tree and the other is in the clear. Using a balanced L tuner I can adjust the taps on the tuner for balanced current. Before figuring this out I had terrible rfi on 20m. Now I have no issues even at legal limit.

At first I thought I made one leg too long so I double checked that. On the lower bands the left side needs more L than the right and it's the opposite on the higher bands.

I'm not a fan of using a balun on either end of an unbalanced tuner with balanced feedline. Not saying it doesn't work. That's what most people use with balanced feeders .

 

So by carefully balancing the CURRENT on the feedline you were able to mitigate feedline radiation that was causing RFI.

That goes along with what I've been reading elsewhere.

Seems that the VOLTAGE on the feedline can still be balanced, yet the CURRENT not be, and the feedline will radiate.

 

I have found with the experiments that the currents can be balanced in amplitude and out of phase resulting in feed-line radiation, but each time when I switched from current to voltage viewing there was always a direct proportion from one to the other [ V ] and [ I ]. At no time was I able to achieve a test where the voltages and currents did not have a proportional value in amplitude and phase they were always synchronized at some level. I think this has to do with my first response to WR2E. It is really interesting to actually 'see' this in real life.

 

I'm afraid our friend Tyler still doesn't quite get it. The CURRENTS as measured by a thermo-ammeter in each wire of the feedline need to be equal. Period. Think for a moment...what is the meter showing then? It's showing the MAGNITUDE OF THE CURRENT VECTORS. No more, no less. The feedline could careless what the phase along its length is at any point.

This is simple high-school vector math here. Each current and voltage has both a magnitude and a phase. If you want to stop feedline radiation, then the magnitudes of the current vectors needs to be the same.

I fear this is a case where Tyler only has an o'scope and so can only think of things from a voltage and time perspective. "Has a hammer, every problem is a nail."

The hams and engineers of the 1920's figured all of this anteena and feedline stuff out without o'scopes. They used paper and a pencil and math. We owe it to them to be able to do the same. Start there. Do the math.

New thought:
Tyler, when you made your experiments did you always use the same antenna? If you did, then it's possible that your antenna is always very ballanced. So you can't help but to see things from the perspective of an already good system. V & I will appear to be closely in-phase. That's beacuse the load looks very resistive; i.e. a low value of jX. But the rest of us aren't always so lucky. The jX is different on each half of the antenna. Go try it. Hang a dipole in an odd way and you'll see things change alot. It's no different than you trying to show folks about SWR issues when you're experiment is only with one good dummy load. It's misleading and fails to show what can really happen.

 

Tyler,
I think the music is an excellent innovation and added a dynamic to what is an excellent production. Stay true to your own style and you will never go wrong. Wondering what is the 10kW balanced ATU on the right hand side of the operating position. I am a dedicated doublet fan, and always interested in balanced ATUs for 600 Ohm feedline.
Peter
VK2OP

 

Thanks for your comment, yes after not watching it for a week I did go to my youtube channel to review the really great comments there as well, lots of subscribers too for one week old. I felt the video was great and very well edited for a novice. You cant make everyone happy all the time...

That is a custom tuner, I made the design for the panels and the meters you see there were part of the design. It has two Gates rollers and a Jennings vac cap. The coax is 'bypassed' it is only a balanced tuner. I have a second part video showing you how to choose the length of ladder line with a given ant you would like that one. I will upload soon. This is the URL of the Ty-Fi KA0KA channel.
https://www.youtube.com/channel/UCOPyqu-ly3yAWd5BQn2Sojg

 

Good presentation. I love the antenna tuner. That's a monster. My tuner isn't that massive, but it does a good job feeding my Delta Loop.

 

Yes it is actually too big, it is 80lBS and too big... I use it for low freq band only when I have to achieve a LOW-Z balanced load on 160M because my 280 foot loop is a half wave on that band. Oddly, the system works fantastic, typically last year my reports were 25 over S9 past 1000 miles on that band.
This year, I may employ a noise sensing ant and adjust my phase and gain in the second diversity receiver to null some QRM out, really cool stuff the 8000 can do in the right hands.

 

"Sunny" or "sonny" boy? Or was that some more of your complex wordplay that I don't understand?

Karma is going to get you for that "CRUSTY" accusation. It may take years, but count on it. Until then, grab a towel and sop up that moisture behind your ears.

 

Couldn't one construct a fairly simple pair of current probes and put one around each leg of the feedline and then into the same o'scope?

I think it would be very interesting to actually use a four channel scope (or two two channel scopes) and view both the voltage and current at the same time.

 

That's what I was wondering. Check this out (also from our great state of Colorado)

http://www.interferencetechnology.com/wp-content/uploads/2012/04/Wyatt_NA_DDG12.pdf

 

Resurrecting an old thread here, I know. I tried something recently with my homebrew link coupled tuner that I have not seen mentioned anywhere. Some quick background: The LCT is pretty much the K1JJ design, antenna is a 700ft+ loop fed with about 60ft of 600ohm 4-in open wire. I get some RFI on some bands, worse on higher frequencies. I wanted to try to measure the imbalance, and ultimately improve it by adjusting the coil taps.

Instead of directly measuring voltage with scope probes, I used a FT240-43 (I had it "in stock") and passed both feeders through it, then put 2-3 turns of wire around it and connected to a single scope probe. The thought here was to detect and measure common mode current, which would be indicative of (im)balance. More current == more imbalance. This current would then be expressed as a voltage on the scope.

It seems to work. I can move my taps around out of symmetry and achieve lower voltages on the scope. Lower voltage correlates with lower RFI into my amplified speakers and such.
Since the comments on this thread were quite informative, I figured I would throw this out there for comment.

Thanks,
Nick

 

Taking a scope out to the atu is still on my to do list. I was able to correct balance issues using a home made rf pick up and measured the voltage from it with a multimeter. Before doing that I had terrible rfi on 20 meters.

Later I found some thermocouple type rf ammeters and rechecked my work. Now that the antenna ends are higher and more symmetrical I have balance when the tuner inductors are connected symmetrically.