Weighs only 265 grams, yet covers 6 bands (40,30,20,17,15,10) without the need of a antenna tuner. I made a small photo gallery at : https://davervel.home.xs4all.nl/PMA/index.html
Yes, interesting transformation of a “standard” Endfed 40, 20,15,10m with 20m long wire.
Will test it on my side too.
Today I was using linked dipole from Sotabeams 40-30-20m and some were asking me to move on 15m and I couldn’t.
Also idea to use Anderson connectors instead of crocodile style is I believe good too.
Thanks and 73 from Thomas F4HPX on Reunion Island
Thanks for sharing, Marcel. This looks like a good and feasible idea for a 6-band portable antenna…
If you don’t mind telling us a bit more about your project, here is a few questions:
- What kind of wire have you used? (Diameter? Isolated? …)
- Any recommendation for the height of the central support and the antenna ends?
- Do you have any swr vs. freq (vs. height) diagrams?
These are the SWR results i got
The wire is copper 0,5mm insulated
The mast used is a DX-Wire Mini 10meter
Like all great things: simple and elegant. Bravo, Marcel!
Well done Marcel !
… but more questions : what coax do you use to the rig, and how long ?
Do you connect any ground/counterpoise wire to the ground side of the 49:1 transformer ?
The coax cable i use is a piece of 3 meter RG-58. The idea is that this acts as a counterpoise (not much is needed for high impedance feeding) so no further connections.
To stop the RF on the outer shield i use 3 RFI clamps at the transceiver side, is that enough? probably not.
Have never seen any need for any counterpoise at QRP power levels as the headfone wire seems to serve well enough. But to answer your question, is that enough choking, understand that the wire going through the toroid doesn’t provide much choking. Choking increases by the square for each additional turn THROUGH THE SAME CORE. Going once through three cores is no where near the choking of going three times through one core. - fred KT5X (aka WS0TA)
PS. Why such heavy wire? I use #28 wire without noticeable loss. And yesterday from New Mexico I worked DJ5AV (I was five watts) with my wire antenna only a few feet off the ground because of high winds. In other words, the heavy heavy pole to get 10 meter height I don’t think gets you anything on a mountain top.
I do not use a choke when using my end-fed half wave and have never had RF in the radio or the operator. Do use about 5 or 6 feet of counterpoise though. Were I to use a choke, would run a few turns of the coax through one core as you mention - the most effective way. My antenna wire is the #26 silky wire, easier handling than hook up wire.
If I understand right this ultra lightweight antenna weights in fact 1565 grams (265g antenna + 1300g pole) and its design seems to be made for about 100 watts (toroidal transformer, radiator wire, insulators, coaxial cable)?
BTW, The efficiency of this massive toroidal transformer is between about 64% @ 7MHz and 70% @ 28MHz due to the only 2 primary turns.
For comparison: The efficiency of my tiny FT-50A-43 (3t/24t) impedance transformer in use with the MTR3/5B (4-5 watts) is between about 72%@7MHz and 76%@28MHz…
You can get that efficiency up to 95% @ 7MHz if you use a Fair-rite 2643625002 core with 3 turns primary.
P.S. More information can be found in this article from Owen Duffy: https://owenduffy.net/blog/?p=12642
Thanks, I’m also up to date - after an intense conversation with Owen Duffy due to his first suggestion for a 6t/48t transformer, hi.
Owen then rewrote his article using the Fair-Rite 2643625002 #43 toroid.
Owen further suggested to use the following complex permeability values u’/u" for the #43 ferrite mix at 5.35 MHz (not listed in his Table 2 so far): 386/232
My actual EFHW impedance transformers (rated for 15 watts) are built on Fair-Rite 2643626302 #43 toroids, 3t/24t 0.6mm wire, mica 120pF/500V compensation capacitor (photos).
Thanks for the details! After an activation on a particularly skinny summit in Alberta last week I’ve come to the conclusion that I need to put a (linked and eventually trapped) EFHW in my arsenal of antennas. It’s been a long learning process but hopefully I’ll have one put together in a couple of weeks.
For some reason pictures aren’t uploading, but here’s a shot from the summit of Mt. Orde (VE6/HC-208). Note the 800m cliff on the left, not a lot of room to run around changing links.
Coincidentally I wrote an article about EFHW antennas recently.