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.
When you’re backpacking and want to work /QRP / P, weight is an issue. Therefore I wrote an artible on building an efficient QRP HWEF using the smaller FT83 and FT140 sized material 52 cores: QRP HWEF. Enjoy reading!
Today I’ve made a 15m L/C trap for my 20-10 HWEF. Click on the link for the article!
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.
Due to the miserably failed 10m/15m vertical HWEF experiments, I have put the old 12AVQ on my chimney. It’s the American version of the widely known (in Europe) Fritzel GP30 from Hy-Gain. It could well be that the Fritzel GP30 actually is a copy of a similar American antenna, I don’t know to be honest. Mine is old, probably 80’s when MFJ did not yet own Hy-Gain. It’s a sturdy antenna and even though the clamps have been replace and the nuts are an exotic mix of everything you can imagine, it still is a nice antenna.
At first I put it on my chimney on a 4 ft aluminium pole but I move it to the flat roof of my dormer so I have easier access to it. I’ve recently slipped on the wet roof tiles (not dangerous, the chimney was in front of me) breaking four of them and got a huge dent in my ego HI. I used two 3/4″ aluminium rods that used to be a portable 10m dipole as radials in N-S direction at 90 degree angle and 5m of wire (1/4 wave for 20m) right down the chimney (no longer in use) so making an angle of 180 degrees. 10m was OK, but 15m and 20m were terrible. To improve things on 15m, I added two MFJ 1615T-ish 15m mobile rods each around 7ft long in E-W direction but that didn’t improve things at all so I removed them. Then I added a single radial for 15m down the chimney but no luck. While I was – litterally – on a slippery slope, I’ve put the vertical on my flat (safe!) roof today. I only installed the 2 x 9ft radials for 10m and Guess what:
The darn thing shows very good VSWR and (!) resonance (X=0) on all three bands. I’m was flabbergasted. Really happy of course, but how this is possible, I just don’t have a clue, maybe you have?
Some important details:
- There’s a choke right under the feeding point; 15 turns of RG58 on an FT240-52 toroid, that should be around 6kOhms on 20m and better on 15m and 10m. I therefore assume the coax’s braid does not act as counterpoise.
- The antenne is on a galvanised iron tile stand with four 12″x12″ tiles. The mast is around 2.5 ft (75cm), the whole construction is 2 x 2 ft (60x60cm)
- The tile stand is on a bitume roof, there’s no metal foil isolation or other metals inside the roof (just wood and rock wool), the flat roof was dry.
- I’m wondering how the graph will look when the roof is wet. I put this line here as a reminder to add that later. I have a suspicion the 10m radials are “coupling” to the roof (in parallel, about 8″ above).
So if you have any ideas, just let me know!
73 de PA3HHO
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)