A SOTA Centric End Fed Half Wave Antenna (Part 2)

Continuing the discussion from A SOTA Centric End Fed Half Wave Antenna (Part 1) - #101 by G8CPZ.

Previous discussions:

I’d agree Andy. Sometimes longer, as you can’t really work out where everything will end up when working from one end. However, once it’s up, that is you set isn’t it? You can change bands at the touch of a button. I must admit, I can’t think of the last time I used my linked dipole.

I’m still playing with mine. As a sloping inverted-L it’s different to inverted-V dipoles. Is it better or easier to deploy? A tiny amount easier to deploy but no idea if better yet. Only obvious immediate advantage is having a tunable AA5TB style match I can change bands quicker.

But going 2m FM only from GW/NW-043 later this morning.

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That’s a good point, Fraser.

With the [centre fed] linked dipole I sit under or near the pole and make my camp there. Once the balun / coax feed is attached, the pole is guyed and raised, I simply wind out the dipole legs in opposite directions. [I always peg the guy strings before raising the pole - best for windy conditions]

With an IV EFHW you either (a) put the pole / EFHW centre support up and hope the wire leg with the matching unit ends somewhere suitable for you to sit, pitch your tarp, etc, or (b) vice versa.

Not with my 40/30/20 EFHW - you have to remove a stub for 30m, which is too high to reach from the ground, so I have to unpeg the wire on that side to lower the wire - just like I have to for my 60/40/30/20 linked dipole for linking / unlinking for 20m.

Actually, I don’t mind jumping up between band changes - chance to stretch my cramped legs / unflatten my aching backside / warm up from the cold.

When my EFHW is an IV for 40m it’s a fallen-over-L for 30m.

I wonder, is the alleged improvement in gain of an IV EFHW worth the extra trouble over a sloper? [I was always pretty happy with the reports I got and gave with the latter]

Anyway, will be trying the EFHW as an IV (first time for SOTA) on Pike O’Blisco G/LD-024 on Tuesday which has a small-area, very rocky summit.

EDIT UPDATE: Activating on Sunday 11th now

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If you have a TRX with antenna tuner, please compare the performance of your EFHW on 30m band without the trap.

I always use my 20m long EFHW on 30m band, with great success. I can’t remember not being able to work a summit that I could hear.

By the way, on 60m as well

73 Chris

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I said “stub” but reading online comments from other users about my [no longer manufactured] LNR Precision 40/30/20 EFHW the rather large inline box with a removable SMA plug link is just an electrical link to extend [or not extend] the wire length to 19.8m for 40m.

I have often [accidentally] forgotten to insert the plug to lengthen it for 40m or remove it to shorten it for 30m. The KX2 internal ATU is so good that it works well on all three bands regardless of the plug status.

I never seem to have the time when on summit to do a A vs B comparison and it would need a willing and patient chaser to help me.

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Am I missing a trick here?

I don’t know if there is a trick involved, but usually I need maybe half of your stated setup time.

My “trick” is that in 95% of the cases, I don’t use any guying. Instead, I just use a simple rod holder described in my document: Portable 7-Band EFHW Antenna
As stated, this doesn’t always work, for several reasons. And sometimes there is not enough space on the summit, that’s why I carry a second smaller EFHW with me that is limited with the bands it’s resonant.

To get a feeling how I setup and tear down my antenna, please have a look at this video: https://youtu.be/z1U7hgbB9RM

HB9BCB

“Easy” is a subjective unit of measurement

This is absolutely true.
The easiest HF setup is probably a KX2 with internal tuner, an AX1 or similar and a piece of wire as counterpoise.

With “easy” I meant an antenna that is not only quick to setup, but also allows to change several bands, with no or minimal intervention. In my case, the antenna must be resonant, because I don’t use a tuner.

There are so many ways to setup an antenna and I’m sure there is always something that can be improved.

73 Stephan

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Hi Stephan,

I couldn’t find the ground mounting mechanism in your 54-page PDF (but I only skim-read it!) but in your video I can see you use a tube mounted on a spike. As you say, that won’t always work.

My Chameleon MPAS Lite vertical [which is my quickest antenna to erect] has a 34cm ground spike and there are many very rocky summits in G/LD (where I mainly activate) where it would be impossible to penetrate the ground enough. So, I have to think carefully about the summit conditions as to which antenna to take.

Even pegs (for guying) won’t go in on those rocky summits or only by 1-2 cm so the pole risks falling over. At least with guy ropes I can use rocks instead of pegs [all adding to the minimum set-up time we measure in the park or back garden].

Also, the north-west side of the UK is often very windy so my four (not three!) guy strings from an O ring on the 6m pole are not an overkill in bad weather.

On the time taken to erect my pole & antenna, as I said before, I take it slow and easy when handling these delicate antennas to help them remain low maintenance.

Tomorrow’s (Sunday 11th) summit, Pike O’Blisco G/LD-024 with its compact rocky summit will be a good test of putting up and taking down my EFHW in inverted v config.

73 Andy

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Hi Andy,

It’s on page 12, and in the footnotes, there are some links to the corresponding product/shops.

As stated, it’s not a 100% solution, but it worked for me on 95% of the summits I visited in Switzerland, Germany, France, Denmark, Italy and Spain.

Further, I omitted that I setup my EFHW as inverted-L, but sometimes the pole is not that vertical anymore, that’s why I call it sometimes an inverted-7 :wink:

73 Stephan

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Hi Stephan, Here is the long answer to why I don’t use your sleeve and spike.

I think the saying, “one size fits all” is the least appropriate for amateur radio antennae and in particular for SOTA.

I carry the following items to secure my mast (when I’m using a carbon6 pole and EFHW) :-
5 pegs
A long (5.5 m) guy rope
3 short guy ropes
guy ring
300 mm long mast sleeve (pvc waste pipe)
the EFHW already has a 2m guy rope installed on the end
Walking poles

Many of my activations rely on speed for success. I erect the mast according to summit terrain and what’s around me.

Option 1. The mast sleeve jammed in rocks.
Option 2. One long guy, using the antenna wire as the other two.
Option 3. Three short guys, either pegged or secured by rocks.
In all cases i attempt to tie walking poles together and velcro the 49:1 to the handles.

I find that in Scotland this covers all summit terrain scenarios. The soil is generally thin with rock or rocks beneath. Sometimes there is no rock on the surface, however the “grass” can turn out to be 20mm of moss over rocks!

I see very little use for a spike in my small granite corner of the planet.

However, always one to try new things, I’m now thinking - can I add one to my pole sleeve, the caveat being it would have to fit in my pack, so 35 to 40cm long max?

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Hi Fraser,

I completely agree with you. Every summit is different and most of your guy thingies I do carry as well, including some velcro.

Yes this is the main problem I’m facing as well. It’s not always that easy as shown in the video. But below the “grass” there is not only stone, there’re also gaps between the underlying stones, you just have to find them, hi.

Sometimes I also have to try 1-2 minutes until I find a good spot, and very seldom I just give up. With the time I developed a feeling where I have a good chance, e.g. by looking at the kind of fauna. For example in the video, I spotted a mossy spot in the forest, and bingo! The spike and holder can also be used to be wedged between rocks and several times I pierced it into an old tree stump.

I’m sure that sometimes I’d be faster with the normal guying approach. I just wanted to give some input for an alternative way, which in average works easier/quicker for me, compared to guying, but YMMV.

I just took a photo of its full length and when screwed in with a cork over the spike. The latter is the way how I transport it in the backpack. The weight is 152g and it costs around 5 Euros.

73 Stephan

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As a portable radio operator who has now become somewhat comfortable, I like to use this “super easy to setup” method on grassy and forested hills and mountains. This means that the 3-way tent guying can usually stay in the backpack…
So thank you Stephan for this tip.

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OK - I admit it: my antenna(s) is no lightweight with 2.1 kg… but this is part of my SOTA-fitness program… and when I need light weight I just take the walking sticks …

I have everything in my self-sewn quiver for that… (even if I don’t always need it)

I tie the DX-wire mini mast with the elastic velcro straps to an existing fence post, signpost,… or I lean it quite simply at a branch. If there is no attachment at all I have the ring for the guy ropes and tent pegs … but I have only needed that a few times.

As antenna I use if there is enough space the Endfed for 40, 20, 15, 10m …or quick and dirty the vertical with the one radial.

Normally i am qrv in 5 min after reaching the summit

73 Armin

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Dear Heinz @HB9BCB,
Dear Ariel @NY4G,

if I understood the whole topic corectly I assume that you both came to the conclusion, that 3 primary are more efficent then 2? Is this correct?

Thx!
73
Julian

Strictly speaking, a large part of my know-how for HF transformers (conventional and transmission line transformers) is based on the findings, publications and software tools of Owen Duffy (owenduffy.net).
That’s why I have always consistently referenced this source of information in my contributions.

The number of primary turns required for the best transformer efficiency depends on the geometry of a toroidal core or the stacked toroidal cores (the decisive factors are the average magnetic field line length and the (total) core cross-section). The expected efficiency can be determined using a toroidal core calculator from Owen Duffy (calculate inductor with ferrite core - rectangular cross section).

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On an activation with @VK3KR a few years ago on Mt Donna Buang VK3/VC-002 we set up my linked dipole and David’s EFHW (20m of wire supported at centre on squid pole, external tuner) roughly at a 90 degree angle. Both went to an antenna switch (a rotary switch in a diecast box) then to a transceiver. Using VK5ARG (Adelaide, 700km) and VK3KHZ (local, 50km) kiwiSDRs on our phones, we did A/B tests, just by flicking the antenna switch.

The results were inconclusive, neither dipole not EFHW clearly outperformed the other, and there was quite a bit of atmospheric/propagation interference which made the test more difficult.

There’s a data point of one.

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I am a vehement advocate of the 20m long inverted v EFHW and have been using it almost exclusively for 10 years and maybe almost 20,000 qso.

And certainly a linked dipole without the loss in the EFHW’s transformer is 1-2 dB better and would theoretically have given me a handful more of contacts.

But I would certainly have thousands fewer qsos in the log due to the complicated setup and replugging of a linked dipole.
73 Chris

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I ran the same test with an 80m EFHW vs 80m dipole right back at the start of my portable operations, operating from Little Kyeburn Hut (ZL4) into the Marahau SDR some 500km away. The two antennas were set up on the same 6m SOTApole at 90 degrees to each other. Switching was achieved by selecting front/back socket on the FT818. There was no discernable difference in received signal on the SDR for a CW carrier between the two antennae - both tuned to read no deflection on the FT818;s (imprecise) SWR scale. Though obvioulsly the directionality of the two configurations could have either counteracted or amplified any difference present in the two configurations.

There was, however, much swearing, cursing and ‘never againing’ involved in the erection of the centre-fed dipole atop to SOTA-pole with coaxial feed, balun and two halves, compared to the simple ‘tie a loop in the middle of the end-fed and hook it over the pole’. Too many cables to tangle over two much scrub, and too much weight / wind resistance atop a flimsy SOTApole. Needless to say, the centre-fed has never been taken out again.

Does that make it two data points?

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The impact of the winding capacities of the secondary winding should not be overlooked.

That’s why the capacitor, usually 100pF, is connected in parallel to the primary winding to compensate for this capacity. Using 3:21 solution and/or a tightly wound secondary, the capacity is noticeably larger than with the classic 2:14 solution. This stray capacitance primarily has an effect from 25MHz.

The 2:14 only causes slightly more losses from 60m and longer…

EDIT Another thought. I certainly don’t want to question Owen Duffy’s comments, but they may not take into account the reactance at the end of the dipole.

73 Chris


1op50-Trafo

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When using an EFHW at the QRP levels you need to pay attention to transformer efficiency, so most of your signal is transmitted rather than converted into heat.

I used FT140-43 a popular core for QRP to run some tests and measure efficiency using Owen Duffy method. Here are my findings.

Tricky to wind method developed by John KN5L gives the best results. Classic twisted wires and crossover is 7-10% lower in efficiency depending on the band.

Since I done these tests some 2 years ago, subsequent tests shown that a FT82A-43 is an excellent choice for a small and light 49:1 transformer. FT82A-43 is like a two stacked FT82-43.

Apart from good matching and efficient setup you need to consider setup configuration of the antenna wire, as this is the very important factor. I tend to use inv-L with transformer at 1.5-2mtr agl and antenna apex at 8-9mtr. Such a setup gives good take off angles on 20/15/10 for DX QSOs.

GL 73 Marek

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