Video: Oscilloscope Balanced Antenna System Tuner Performance Test

Nice job. I like the video. Don’t worry about the nit pickers. I am trying to learn this type of testing and your video,caught my eye. I thought it was interesting and hope you can explain more, some of the basics: for example when you say you applied a carrier, what did you do? CW signal. How much power? When you connected the scope probes, did you go direct or did you have a buffer or something to prevent to much power from going tot the scope?

Thanks,

Tom
KB3ONZ

 

I don't know, I kinda liked the music. He isn't operating, helps bridge the camera switches. Besides, I learned something.

 

Thank you guys for your kind words, this is the first video I have ever made and thought it was well edited on a subject that has been missing in demonstration! The carrier was only 5w, the tuner selected for the demo as seen by the back of the tuner was a commercial Palstar AT5K because it is a widely used product and would be more relatable to all HAMs, not the 80LB tuner in the opening shot reel as it is perfect and no one else has it because it was a one-off unit, therefor, I felt it would devalue the video if I used it.
Thank you all for your kind words, I will be continuing my post on my ty-fi KA0KA youtube channel as well.

 

Okay I tried the experiment, I have over a half a mile of 600 ohm feed line feeding various antennas. I had been using a current meter before and that provided me some initial relative information. I was able to make a few adjustments using oscilloscope technique, very helpful for the rhombic antenna setup and the matching networks that I have here thank you

 

Tyler-

All music and such aside...

I think you missed an important "teaching moment" in your video. I don’t recall you saying that voltage balance implies no feedline radiation, and it never does. For that, I thank you.

But what you could or should have emphasized was that any feedline radiation from open-wire line is actually caused by CURRENT imbalance. Showing what the VOLTAGES are on an open-wire feedline, even if interesting and educational, tends to overlook one of the most important facts about open-wire, that being: unless the CURRENTS are equal the line will radiate transmitted signal. That's a sure way to let RF into the shack and not where we want it.

Any coaxial-based antenna tuner feeding open-wire should have a current balun as the last item before transitioning to open-wire. For those who may doubt, try it in any NEC-based simulation and use two but unequal current sources. Excellent references have been written, one is titled “Reflections” by W2DU. Another is an article in March 1983 QST. Hams should give both a good read.

Voltage baluns came into popular fashion for coax-feed dipoles ages ago, are cheap, easy to build, and still sold as part of low-cost antenna tuners. Current baluns can be harder to build but are worth every penny. I believe your Palstar tuner uses a current balun.

Perhaps in future videos you can point some of these things out. It will make for a more complete understanding.

-Brian

 

Fantastic video and editing caller. Don't know what's the deal with all the soundtrack bitching coming from the crustations.

 

Hi Brian and to my 14 year old neighbor Evan!
Actually, the AT5K used a really smart idea of putting a current 1:1 unun on the input of the tuner network. I removed the original one and put in a custom made 4 core 1:1 unun for better performance. I made a separate video on that mod and comparing it to other tuners, such as the Millen 92200 unbalanced tuner. I wanted to keep this as simple as possible for the demo. The large tuner uses current transformers feeding a demodulator that feeds the DC to the actual current meters, but no one owns that so I choose to use my AT5K for the test to give more value to the video more relatable !
Modification to my AT5K custom 4 core 1:1 UNUN on the input of AT5K network

 

Please explain why that is a smart idea

 

Evan,

Did you mean crustation or crustacean? They're quite different, lad.

Perhaps in time you'll understand why some of us prefer listening to content without the distraction of a background track - regardless of the musical genre.

I don't listen to music with a background track of someone explaining electronic theory...

 

Tyler-

Please tell us why the balun on the *input* of that asymetrical T-match Palstar is a good idea?
-Brian

 

Tyler,
You went through a big long procedure to 'prove' the voltage to 'ground' on both sides of the line was equal.

Once you calibrated both channels to the same source, when checking for equality why didn't you just use the INVERT switch on one of the channels of the scope and lay one channel signal on top of the other. Most scopes have the ability to invert the signal from at least one of the channels. Laying the two channels on top of each other is quick and very easily shows up any imbalance in level or phase difference. Just a thought.

Some have suggested using two ammeters to measure the currents and that is one way of doing it but who has two RF ammeters. (Have you priced them lately?) Also, using two ammeters gives you absolutely no information on phase imbalance.

Dave K3GAU

 

Nice video. Agree on the music. Very nice and clean looking shack. What are you using as the controller between the radios on the desktop. I like how it seems to match well with the keyboard.
73,
Tom AJ4XM

 

Hi Dave, yes this was a demo only and as such it had to be illustrated for as many people as possible. Some scopes, I have had questions on from clients of my CleanRF Systems work have shown not to have this option thus I filmed this just like I wrote the Applications page on my CleanRF site, as universally correct as possible. Also, my two current meters you see there were custom built by Simpson, they are $130 each just for the meter since you asked!
As you also indicated, my current transformers and meters will never show you the phase difference as demo in the film as you also picked up on! I have done a summing amplifier to one meter as well, so if if the phases and magnitudes are equal the meter stays in the center, but now we are getting too far into the weeds! Good questions!

 

Now listen here sunny boy, I was referring to you as CRUSTY. Obviously you don’t understand my complex wordplay.

 

Tom thanks for your comments! I have a separate video that goes into each component of the shack, some of the things happening are really cool such as the Adaptive Pre-Distortion system giving me a system wide linearity correction in phase and magnitude to improve your over-all IMD 1000X leaving the shack, it is wonderful.
Some of the info in on my QRZ page some not, it will all be posted on my youtube channel in the near future, you can always get the direct notifications if you subscribe the current name of the channel is Ty-Fi KA0KA (Ty-Fi was a nick name I was given years back with my audio friends hihi)