80/40 HWEF looking good!

Cut the wire in between the transformer and the 40m L/C trap with 30cm and the dip was spot on. Resonance on 80m was still a little low (around 3.6 MHz) so I cut the tail wire after the trap with 20cm and folded back 10cm. Here are the results!

27.07.2020 80-40 HWEF with QD trap 3200 - 7600 kHz

Now that’s a pretty picture… Let’s zoom in:

27.07.2020 80-40 HWEF with QD trap 80m

Because the half wave for 80m effectively is loaded with a 20 uH coil the bandwidth is a little small but still under 1:3 on the whole band and 1:1.45 at best. I found that the R of the antenne on both 80m and 40m is a little over 50 Ohms so I will probably add a turn or two to the transformer. Not sure which one I’m going to use though. I might first want to try the multicore transformer configured from 2 x FT140-52 and 4 x FT82-52 inside but I might as well be using the single FT240-52 transformer with 4:28 or even 5:35 ratio. Here’s what 40m looks like:\

27.07.2020 80-40 HWEF with QD trap 40m

Nice! Better the 1:1.7 on the whole band. Also here the R is a little too high so a little more transformation is required. Will do that later, first test this to see how it works.

I’ll keep you posted!

73 Pleun (PA3HHO)

Working on the 80/40 HWEF again…

I tried to span away 40 meters (120 ft) of wire in an effort to do some testing on a wideband antenna (the well known full-size 80 – 10 version) but I just don’t get away with the length. I have to zig-zag all over the place and when I tested it with one of my auto transformers, the resonance on 80m (half wave) was too low and on 40m (where it’s a full wave) too high. Shortening the wire would improve on 80m, but will move the resonance point on 40m even higher so that’s a dead end.

27.07.2020 40 meter long wire with triangle end

While I decided to opt for a dedicated 80/40 aerial AND a dedicated 20/15/10 antenna (wire or vertical), I’m taking the wire down again and will replace it with a single trap for 40m. Because I’m not sure how much inductance the trap needs to get a “practical” tail wire (around 10 meters long, that I can span away), I decided to make a quick and dirty trap just temporarily. When I’m happy with the performance, I might be making a more permanent solution but experience learns that in many cases, my temporary solutions become semi-permanent HI.

I took one of my old trap coils that’s wound on a Fritzel isolator. It’s about 40 turns of enameld wire .8 mm in diameter. Because I hate to remove and add turns to a coil to get resonance when using a Russian door knob type capacitor, I decided to just leave the coil fixed and cut a piece of normal 2 conductor home appliance wire to length.



The coil measured around 22 uH. With 31cm of wire that measured 22 pF (so .7 pF per cm) I found resonance around 7,646 MHz. I know my L/C meter measures capacitance pretty well, sometimes I doubt the inducatance measurements. Calculating back from the resonance frequency and the capacity, the coil calculates to 19,9 uH, not bad. I used that value to calculate required capacity for resonance around 7.3 MHz which is 23,9 pF. To get 24 pF, 34cm of wire required. It’s nice to see that – now and then – theory matches practice HI:

27.07.2020 QD 40m trap resonance

I think I had 20 meters of antenne wire lying around from my previous experiments, I’m going to hook that up to an auto transformer (for testing I mostly use the one with 2:14 ratio on single FT240-43 with single FT140-43 inside), hook up the trap on the other and and a random length tail of about 12 meters and let’s see if I can get it nicely in tune on 80m and 40m. First test looks very promising:

2020-07-27 80-40 with 20m wire - QD trap - 12m wire

Going to cut the length of the wire between the transformer and the trap about 20 cm to get a dip around 7.1 MHz (now a little under 7 MHz), that will move the dip on 80m up as well, maybe it’s spot on.

Will keep you updated!

73 Pleun (PA3HHO)



Trapped HWEF for 20/15/10

Today I spend almost whole day cutting my 20 – 10 HWEF to length and running up and down the stairs (shack to garden and vice versa). The auto transformer is based on a single FT240-52 with 2:14 ratio. The wire has a trap for 10m and a trap for 15m. I will measure the exact lengths in future, probably will add another page on it in the HWEF menu.

The antenna wire is sloping in a steep angle down from my roof, I was hoping it would have a but lower radiation angle that way then the 80/40 HWEF that I used on 20 as well (that when is lightly sloping, almost horizontal). I will experiment with different directions and angles. The results so far:

25.07.2020 20-15-10 HWEF 20m
20 meters is looking good!


25.07.2020 20-15-10 HWEF 15m

I still need to shorten the wire in between the 10m and 15m a little to get the dip around 21.250 but for now it’s fine. Shortening this wire will also have impact on 20m so I will have to lengthen the tail wire.

25.07.2020 20-15-10 HWEF 10m

I had a nice dip around 28.500 MHz with very low SWR, but for some reason the R went up to 65 Ohms and the SWR went up, not sure why. Still very acceptable for the SSB part of the band.

For now I’m happy, will be doing some testing the comings days. I’ll keep you updated!

73 Pleun (PA3HHO)

HWEF mix 52 material core experiments

It’s been a while… I’ve been busy with work and family but now the holidays are here, I have some time to play radio again.

Past months I’ve been experimenting with a mix 52 multicore transformer built of two FT140-52’s with four FT82-52’s inside. Total Al value of this configuration is 1170 and the transformer has a turn ratio of 3:21. According to Owen Duffy’s Calculate ferrite cored inductor (from Al), the efficiency on 3.6 MHz is 99.5% meaning 0.02 dB loss. I must be doing something wrong HI (I asked Owen, hopefully he’ll get to me soon).

I took the trapped wire from my 80/40 HWEF down and tried to span away 40 meters of wire. The last 10 – 12 meters are going down 6 meters from a tree, then 3 meters to the left in parallel to my (metal!) fence and then 4 meters up again so the aerial’s “tail” has a triangle shape. On paper it looked good, but in practice it’s really not. Resonance on 80m is OK, too high on 40m and 20m. I also noticed that the R went down when frequency went up. Op 80m the R was around 35 Ohms, on 40m and 20m it was around 25. Not a real problem for now, changing the transformer ratio will probably fix that. I tried to compensate the (terrible!) performance on 20, 15 and 10 meters by adding 22 pF, 69 pF, 100 pF, 122 pF and 147 pF but this didn’t seem to improve things.

Conclusion: the 6-core transformer will probably work well on 80/40 but the bandwidth is too narrow to use it on higher frequencies. This didn’t come as a surprise because the total Al value of the cores was around 1170 which with 3 primary turns results in 10.53 uH inductance, that’s even higher than 3 turns on a single FT-240-43. Even though the efficiency of the 43 material might not be optimal, it seems that the lower Q allows for more bandwidth making it still a good allround solution for a 100W wideband HWEF. If you need decent performance, use 3:21 ratio on a single FT240-43 when 80m & 40m are your favorite bands and use 2:14 ratio for decent performance on 80 – 10 meters (optimum on 40 and 20 meters)

Coming weeks I will be testing my 20/15/10 HWEF that’s using a single FT240-52 core with 2:14 ratio. It now has a 15m and 10m L/C trap with moderate inductors, total length is around 7 – 8 meters. I also started experimenting with a new transformer that has a 4:28 ratio on a single FT240-52 core. I’m hoping to use that on 80 and 40 meters. I already did some testing and found that, without compensation capacitor on the input, it only seems to work well on 80 and 40 which is fine for my purpose. I will add a 40m trap to the wire to enforce the antenna is half a wavelength on both 40m (trap electrically disconnects the tail wire) and 80m.

I will keep you updated! Stay safe everybody!

73 Pleun (PA3HHO)

100W mix 52 based HWEF design

I’m very exited to tell you that I’m working on a new 100W HWEF transformer design based on smaller 52 mix ferrite cores. I’m also happy to inform you that Owen Duffy (VK1OD) himself is helping and advising me in the process. As I’m still experimenting I will not publish any results yet but I it’s looking very promsing.

IMG_20200420_114944087 (1)

Continue reading

New HWEF articles!

I’ve written two new interesting articles about the HWEF:

New HWEF dedicated to 20/10 with single FT240-52 (updated 26-MAR-2020)
Yes! Finally succes! Because of the limited working range / bandwidth of the 1:49 autotransformer (UNUN), I’ve succesfully built an endfed tuned to high frequencies using a single FT240-52 with a 2:13 ratio that seems to – finally – work really really well!

HWEF: what toroid(s) to use?!
Everything I know/learned until know about designing the (in)famous 1:49 auto transformer / UNUN and how to optimise it to meet your specific requirements.

HWEF articles!

It’s really rewarding to notice that many people all over the world have read and are reading my article on the multi/any-band HWEF. Please be aware however that this article is from 2011 and I recently (winter 2019) have published an article on the (limited!) bandwidth / working range of the HWEF 1:49 auto transformer . I’ve measured four different transformers including the Steve Ellington (N4LQ) design. Highly recommended! I’ve also written an update on the trapped 80/40/20/10 HWEF  I’m using nowadays.

Then… I recently did some experiments with a vertical HWEF for 10m/15m with a FT240-52 based 2:14 transformer on 10m agl. I should be a low angle canon blowing the dx out of the water but… It didn’t. My calculations and measurements on (several!) transformer(s) and (several!) L/C match(es) looked promising but in practice, the antenna miserably failed the tests. I’m still figuring out what went wrong, can’t get my fingers behind it yet. So there you go, not all my experiments have good results, I guess that’s the idea of an experiment. The challenge is of course to find out what is wrong so… I’m not giving up on this vertical yet but after three weekends of work, I took my loss and put the old Hy-Gain 12AVQ vertical back on the chimney today HI. I will keep testing the 10/15m concept with some sloping wire (instead of a vertical aluminium tubing pole), see if I can get it to work.

Happy Holidays for you and your family and I wish you a radio active 2020!

73 de PA3HHO (Pleun)

Amidon / Fair-Rite toroids

I’m have ordered a lot of toroids at Mouser.com, way more than I need. If you’re interested, in Amidon (= Fair-Rite!) toroids, let me know, I have some spares in my shack.

FT240-43 €8 (HWEF 160m and higher frequencies, CM choke 80m/40m)
FT240-52 €12 (HWEF 80m and higher frequencies, CM choke 40 – 10 meter)
FT140-61 €4 (1:1 balun, 1:4 balun, 1:9 unun, rfi surpression)
FT140-43 €4 (HWEF 40m – 10m, CM choke, rfi surpression)

If you need more than one or two toroids, I advise you to order directly at nl.mouser.com because that’s what I did. Bear in mind that shipping costs are €20 for orders under €50 and all prices shown are excluding 21% Dutch VAT (exclusief BTW) so you need to add 21%.