During the last few months I have tested lots of wire antennas. Forgetting the theory and looking at what works in practice, the EFHW was the shining light for multi band operation. I like to get out and activate parks under the World Wide Flora and Fauna program. (Also POTA) In a three hour session I normally have around 50 contacts including stations in New Zealand, Europe, Japan and the US as well as my home land in Australia of course. I build my own transformers and run 20W. Gotta love the EFHW.

Thanks Colin, nice one

Kudos for going to the trouble of testing - and I enjoyed your video. Thank you. May I suggest calibrating at the fixture - screw terminals - where you connect the transformers as there will be losses in the BNC and the screw terminals. It would make an interesting follow up - and I may well be wrong. Yes it might not be a lot but it will add to uncertainty. I've used this method also and found it agrees with a simple link and then using Rp to calculate efficiency for the lower bands, but diverges from the single transformer and terminating resistor approach. From the shape of the S21 it is suggesting that an extra primary turn may help on 160m but will most likely make 10m worse. Getting broadband over 160m - 10m has defeated me in the past. You can do a heating calc from those figures also. Again, thanks for the video.

Great work Colin, very interesting to see the results!

You can do a better test with the VNA. Use a single transformer, and for the output load, use a 2400 ohm resistor in series with a 52 ohm resistor. Feed the junction of those into the VNA which will see close to 50 ohms impedance. You have to correct for the attenuation due to voltage divider of the two resistors. This measurement eliminates the double hit of the two series leakage inductances of the two transformers. With the single transformer method, you only see effects of leakage inductance from the single transformer. -Steve K1RF

That was very interesting as I use the 40m EFHW almost exclusively. I use 43 material in my toroids so not sure how much the results would differ between the two materials.

It would be interesting to see if different mixes in the cores would improve the high bands of changes in capacitor values.

Really interesting video Colin, I do have a VNA and have experimented like this. I was also wondering, as I have a 2 ch Rigol scope and a signal generator whether another method could be to connect my generator (which has 50 ohm output impedance) to the transformer primary then compare the output level on the secondary. I suppose the only difference would be the scope has an high input impedance. Then I thought about putting a T piece on the secondary scope probe with a variable resistor and I could then adjust it for maximum output, measuring the resistance could then give me an accurate turns ration 2450/50 etc. Does any of this make any sense to you. Main advantage is I only need one ferrite to test.

Good stuff. How much coupling did you get from having them next to each other? Is there an effect from the desk? Ie metal frame etc

Newbie question here: Is it possible to measure the loss and performance of a transformer purchased - without having a second identical one? I bought two to experiment with - but would love to know the characteristics of each.

Colln, did you measure the loss of the two test leads incl connectors?

So, it is evident that the loss of high bands has been confirmed so many times in the last 7 years. Unfortunately, amateurs keep looking only at SWR which is great on high bands due to simple attenuation of reflection on the way back thru the transformer, just like you see low SWR at the radio side when inserting long and lossy coax. The Insertion loss of less than 0.5 dB 3-30MHz is possible, see the MEF-330-1K+ with three 2.4" cores stacked.

H.A. 2 STACKED FT240-43 ?

Proven yet again that the 3 stack of 52 mix is NOT an efficient 80m-10m antenna. I can think of at least 4 people now that have shown this sort of measurement, but the masses keep building these inefficient transformers anyway. 🙄

Tu calibración no es correcta, tienes que calibrar con los dos cables juntos en serie, saludos.