Hello fellow hams, i’m looking for a homebrew Vertical Antenna for 40M that has centerloaded coil and a two(2) pieces of wire radiator that has a length designed to possibly fit my 19.6 Ft. Tactical Mini pole using my 49:1 EFHW Transformer.
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For an Endfed I guess the coil will make it very unefficient.
One (floating) radial will fit on every summit.
The trouble is that with a half-wave you would have the peak current (and therefore maximum radiation) at the centre of the wire - in exactly the wrong place to put a centre loading coil.
It would work better as an upper-and-outer type L dipole with loading coils in the centre of each of the legs. In that case each leg is a quarter wave and the peak current is at the feed point. No balun is then required.
Hello Jo, i just read both antennas and really appreciate your recommendations. I am not so sure i’m gonna make those but all i want is simply a vertical wire and a coil to feed it with my 49:1 UNUN since i don’t intend it to have a counterpoise, instead the coax maybe the one to function
Ah okay. Now i just reminded by your explanation. How about repositioning the coil at the base?
I think that is hard to get working well - my experience is that short end-fed antennas work best with a resonant tuner rather than a simple balun …
@MM0FMF’s link is a good one to follow up
That link is reminiscent of many loaded verticals. I made a Buddistick clone to fit a short pole and worked plenty of stations on it till the Solar flux dropped. I switched to Inverted V dipoles then. But Old Sol is well out of her slumbers so it may be worth trying this kind of antenna again.
The only thing I know from using something similar was it was a bit poor on 30m being so short and would expect this to be even worse on 40m being so short and thus quite a compromise. But it’s a few bits of wire and a some plastic tubing. A few hours to put it together and then compare it against a full size Inv-V. Endless fun
Thank you much Andy for this new idea to me. I am so excited to hopefully build this as soon as my available time permits. I’ve been using an inverted V and i miss using this kind of portability.
I am pretty happy with the design I used on the Matterhorn:
It is basically a up-and-outer with a high-Q loading coil at the base, a ca. 4.5m radiator and a T1 autotuner as an essential component.
I plan to evolve it so that the T1 will be replaced by a built-in variable LC- match and a Tayloe SWR indicator.
You can also use the autotransformer matching unit from a miracle whip antenna (from ebay) and attach a 4-5m radiator to it; this should be much more efficient yet ultra-portable and quick to set-up.
73 de Martin, DK3IT
Hello Martin, you had a good idea but i will definitely not using my qrp set up with a tuner. Thank you for your reply.
From my experience, you roughly have three choices for a SOTA antenna:
Spacy summit, no total hurry (total time on summit> 20-30 min): trapped EFHW, inverted L or inverted V. I use that 80% of the time.
Small summit, some time on the summit for tuning the antenna due to effects of soil and radials position: Resonant/matched vertical.
I used this in the past:
But the exact match is unpredictable; and it can take 15-20 minutes to adjust the radials until you reach an acceptable SWR.
- Small summit and need for quick activation (<15 minutes in the summit): Vertical or Up-and-outer with a tuner, be it inside the antenna, an Elecraft T1, or inside the rig.
Note that the varible LC match in my planned next version of the Matterhorn design will only compensate for the small bit of mismatch due to soil and radial deployment. The main loading coil is from 1-1.5 mm silver-plates copper, hence high Q.
It is maybe 1 S-levels, max two worse than my trapped EFHW, but has never failed me so far.
When my design is done, I will try a few WSPR comparisons.
73 de Martin, DK3IT
I use a modified LDG 17 1/2 foot collapsible vertical. I replaced the wire with more flexible wire and added a banana size socket to the wire at the top. I use an ATU at the base and two near ground 22 ft radials. Works on 40 m and shorter wavelengths. Adding a 24 1/2 foot sloping wire to the top allows me to work 80 m and get out better on 40 m.
Lengths are not critical. No trauma over calculating loading coils, no worry about high SWR. The efficiency of the atu would not be worse than a loading coil and balun combined.
I use it where driving a spike into the ground is not possible - it has a 5 legged steel tube base. Minimal footprint. Great for operating at the side of a track. Radials laid on grass or bushes or rocks parallel to path.