The 4015
I pretty much gave up on multi-banded EFHW antennas because the harmonic either didn’t work out or the efficiency was super poor. I set out to try and rectify that. I tried to build an EFHW that had the typical 40M, 20M, 15M and 10M bands. I only got 3 of them in the sloper configuration.
Enter: 4015 Build
Wire Winder
I have never had a wire-winder antenna before so I got VE5ARV to print me one of Ham Radio Dude’s. It turned out excellent!
Core & Cap
I wanted to use a more efficient core than the typical 140-43. So I decided on the Type 61 2661102002 (Size: 1.020” (25.91mm) OD) popularized by Evil Lair Electronics. But in my build I made it a 49:1 ratio with a 100pF capacitor, hoping this might be more cooperative with the harmonics…spoiler: it isn’t.
Initial Setup
Using 66’ of 22AWG wire, I set the antenna up out back in the testing area and found that as I tuned for 40M, the rest of the harmonics went to pot. This has always been my experience with multi-banded EFHWs which is why I gave up on them. But I was committed to make this work. So I went to plan B.
Compensation Coil
Rumour has it that adding a small coil 6’ from the feed point can have the effect of bringing the higher bands back down into resonance. So I got VE5ARV to print me one of Ham Radio Dude’s coils. I did about 11 wraps as per the instructions but it wasn’t enough.
I went and cut a double length coil former from scrap PVC. It’s about the same .75” diameter but ended up being about 6cm long - enough for double the number of wraps. It ended up being about 18 or 20 wraps or so. This worked to bring 20M and 15M back into harmonic cooperation but unfortunately 10M remained a wild horse.
NANO VNA Sweeps
As you can see, the coil did pretty well in bringing the harmonics back. Everything is under 2:1 except 10M which has gone rogue.
Pig Tails for Ham Radio
I thought about this build again and I wondered about adding a pig tail to the EFHW wire to physically lengthen it and hopefully bring 10M back into the fold. Adding a Wago lever nut to the end of the wire allows for a short little piece of extra wire to be swapped in easily if you want to work 10M.
So, it’s still not very good. But it does give a slice of 10M under 2:1 SWR in the lower SSB portion. At least it is somewhat usable now - and if you had an internal rig tuner it could clean it up no problem.
Conclusion
I’m pretty sure this build is going to perform better with less losses than using the typical Type 43 core. However, it is kind of a bummer have to fiddle with 10M. To me it’s not a deal breaker by any means because 10M is hardly ever open here anyways. But, it’s a matter of principle. This should work! It might be a combination of the core type as well as the winding pattern of the toroid. I could have bumped it up to a 64:1 and used a 120pF as per Evil Lair’s build and this might have helped bring 10M back into the fold without the pig tail. But as it stands now, I’ve got 3 usable bands on a very efficient core without a tuner, deployed as a convenient sloper.
I tried a quick 5 Watt QRP SSB contact and was able to hunt a POTA station, KD0B in Minnesota. He was 59 and he told me I as 58. Not too shabby at all!
73 de VE5REV