You might compare the effectiveness of 4:1 and 9:1 current baluns at extending the range of a ATU with end-feed antennas. I recently checked out how well my Emtech ZM-2 tuner worked Nelson Antennas's 9:1 UNUN. I was impressed. While I could get the ZM-2 alone to match 29- and 41-foot non-resonant, end-fed wires on 40 meters, the 9:1 UNUN made the normally touchy tuning of the ZM-2 much easier. Watching the adjustment on a NanoVNA, all I had to do was adjust the left knob to bring the low SWR onto 40 meters and then adjust its depth with the right knob. I also realized a downside to the current focus on half-way end-fed antennas with 49:1 baluns. Because the half-wave is resonant, any move off-resonance creates issues. Never being resonant in the first place means non-resonant antennas are less temperamental. I use a QCX-mini, which doesn't have an ATU, so I need that ZM-2. But for those whose transceivers have a built-in ATU, a 9:1 balun might spare them the expense and trouble of an external ATU. The question might be whether 4:1 is enough or if 9:1 is better.

The SWR test does not tell you anything about the balun's ability to minimize common mode current. To do that use the nanoVNA to connect one end of the balun to the port 0 center pin and the other end to port 1 center pin. Then read the S21 LogMag which will give you the "Transmission Loss"" in dB across the HF frequencies. You want at least a 20 dB loss ( blocking 99.0% of common mode current or, even better, a 30 dB attenuation, blocking 99.9% of common mode current). The nanoVNA will also give you the balun's impedance but you will need to export the S2P Touchstone file into a free program available on line called Zplots. The VNA will not display accurate impedances natively or using the nanoSaver pc software. I love your videos!

Killer video as usual!!

I am just getting interested in antenna geekery from watching you and Coastal Waves. MFJ is closing down but found one at HRO. Looks like it will save me some trouble collecting or building several items. Thanks .. My G90 just might make it outdoors when the weather cools down here in Florida.

Nice Video , cool that you opened it up so we could see the construction 73!

An interesting exploration! Thanks for making this

Well, go figure... I type in mfj 911h and there's and Ape video for it! Let's watch and see if it's worth a hoot

Good explanation

Made in the USA :) Thank you for showing us this! 🤜🏻👍🤛🏻♡♡♡

I watch all your videos...jus sayin.

Hello, I'm studying to get my amateur radio license in the mean time I'm on the 11 meter band CB) to get some experience on ham talk. I have a question to ask. I live in a apartment where i can't put up a antenna my only option is a long wire antenna would this balun work on long wires?

Thank you for this. Bring a newbie and having a fascination with loops, how would this work as part of a Delta Loop? Thanks in advance.

So when you put roids in parallel, they are supposed to interact, right?... I wonder how MFJ handled that.

I wish MFJ would send me a box of stuff lol