I’ve found the performance of a 1/4wave GP with 3 1/4wave radials sloping down at 45degs to be repeatable on 12 and 10m. The sloping radial does make a 20m 1/4 wave too big for my poles.
I also have 1/4 wave GPs with sloping radials for 20, 15, 12 and 10m. They all work well with the US and Canada consistently worked on all bands. Best results were VK and ZL on 20m and Argentina on 10m. The 20m GP needs my 10m pole; the others fit on the 6m pole.
They are single band but are pretty quick to put up and take down.
EDIT: This is with 5W CW except on 10m where it is 3W.
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I settled on elevated radials for this reason, by using elevated radials over ground laid radials you remove the issue of ground loss and detuning. Each 1/4 wave radial on the ground is no longer a 1/4 wave, in fact it’s a different length on different ground … Electrically.
To multiband such an antenna could easily be done with link’s and M7BIA did this with a two band version. For the same match over differing grounds I would go with elevated radials.
Sean / M0GIA
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Hi Matt.
I only use 1/4 wave when I know there isn’t enough room at the summit.
I use an unbranded Chinese telescopic antenna of 5.2m long and 10 radials also of 5.2m
I made marks on both the antenna and the radials with an indelible marker for 18 and 21Mhz since when fully extended it is perfectly adjusted for 14Mhz. For 7/10Mhz I use a coil.
The radials in 14, 18 and 21 are extended as far as possible evenly separated from each other. But for 7/10 I join 5 radials in one branch and 5 in another branch and I extend them in opposite directions since it’s the only way that I can tune the antenna. I have no idea why but with this antenna I have worked the most of my QSOs with Europe as well as S2S with USA and Oceania.
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I had mixed results with swr / tuning on verticals, similar to yourself. I did find that sloping radials were better. I used a 7m pole with a 5m vertical, which gave me over 1m above ground for sloping radials. I didn’t get into coils / switching, but I spent ages tweaking the radials almost every time that I eventually got fed up and now almost exclusively use a 20m end fed wire in inv V, or L if space is tighter.
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I tried quite some designs of SOTA verticals, e.g.
The key lesson learned is that it is not possible to design a tuned version that would work without a tuner in varying deployment conditions, e.g. ground characteristics, radials deployment, etc. If you have a lot of time on the summit, you may be able to tune the antenna by playing with the radials deployment, but that is annoying and not guaranteed to work.
So my next design made the Elecraft T1 tuner the center of the design:
The core idea is to do the biggest part of the compensation (for 40m, mostly), by means of a high-Q inductor at the feedpoint, and the fine-tuning by the T1 auto-tuner. This allows for fast deployment in varying environments.
The next planned iteration will replace the T1 by a simple LC match and either a Tayloe SWR indicator or the BlinkySWR. The L of the LC match will be just a bit of extra inductance on the loading coil, so I hope to need only a variable capacitor and maybe 1 - 2 switchable additional Cs in parallel for ca. 20 - 1000 pF.
But the main lesson learned is that neither a vertical nor an up-and-outer matches reliably in changing deployments. Most success stories are based on just too small a sample size ;-).
73 de Martin, DK3IT
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Some years ago, when starting doing activation for SOTA I built a compact multiband vertical antenna. I wanted it for 40-30-20 meters, and decided to have it center loaded, instead of base loaded.
I prepared a quarter wave for 14 MHz firts, with a single sloping radial.
Sure an elevated radial would be better, but I decided to have that sloped radial for ease of final tuning, as there are variation between summits. Having the chance of reducing or enlarging its lenth over ground was the easier way to have some flexibility. In the end it was very easy to fine tune for minimum SWR this way.
Then I added a custom made center coit with two taps. The coil was bypassed for 14 MHz but the taps were used for 10 or 7 MHz (10 uH / 25 uH).
Regarding the radial, the length was increased according to the band in use.
With this aerial I did some succesful activation, knowing that it’s a compromise antenna, but it was fast to deploy and quite appropriate for reduced space summits.
I’m currently using a multiband EFHW and find it a better performer than the shortened vertical, but I would consider the compact vertical again for these reduced space summits.
Using a single radial is easy and convenient for a fast tune process: you forget about the fixed length vertical radiator and simply adjust the radial length for minimum SWR.
73 de Ignacio
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Wow! Thanks for a wealth of good replies there.
I feel there are 2 potential reasons for ‘going vertical’:
- Small footprint, rapid deploy SOTA antenna with easy multi-band operation
- Low-angle SOTA DX antenna
My motivations lie 95% with option 1 - the small footprint, easy deploy, rapid band changes. Something for tight summits (or crowded caravan parks) where stringing out an EF-40m-HW is not a good option.
Given that, I acknowledge all the really great advice on elevated 1/4 wave radials - and if I do decide to build a vertical for chasing DX, that will all be really helpful. But for my current purposes (limited space, fast deploy), if I can string up multiple elevated 1/4 lambda radials, then I can deploy the EFHW - so I’ll not be pursuing that direction for now.
@EA2BD - your solution looks very similar to my first (failed) attempt at this, except for your elevated feed-point and single tunable radial. I had no success whatsoever with the single snaked ground-laid counterpoise, but never tried tuning it or sloping it.
I will certainly play with that design, though it’s benefits for small summits depend on the length of that single radial.
- I note the 1:1 UNUN - so you are feeding this as if it were a dipole at 50 ohms, not a vertical over groundplane at [EDIT] 36 ohms as I am?
- What is the length of your single sloped counterpoise. I’m guessing 1/4 lambda given the dipole-like impedance?
==
@DH5ST. So 4 counterpoises @ >=0.1 lambda was where I started with the ground-laid counterpoises I have currently. Switching from a single long counterpoise to 4 x 5m ones made a huge improvement in consistency, just not quite enough to avoid having to tune the antenna each deployment. I could go for more radials as @JP3PPL does, or longer (10m?) radials as @VK1DA mentions for 40m - it would be a good experiment at least to see if either decreases the variability in tuning (and if so which solution I find least inconvenient to deploy)
==
@DK3IT - On first read, I was silent screaming ‘but I want a tuned antenna, not an antenna tuner’. But rereading your points and thinking more clearly you make a very valid point:
- The antenna is very close to tuned by the large centre-loading coil - generally needing shifting only a couple of hundred kHz to get back onto the desired frequency. So a very small adjustable LC (or even just C) tuning circuit would indeed probably do the trick. Something small enough to build into the UNUN case to avoid assembling additional connections & components in the field.
Thanks also to all other contributers not directly mentioned here. All posts above had useful advice in them. Feel free to scream out if I’ve missed or mis-interpreted your points.
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Hi Matt
Let me throw another less common option into the pot …
A lot of this discussion has been around radials or counterpoise wires, raised or not. I use a different option here for the home vertical HF antenna and that is a “Loop on the Ground” antenna earth. Similar in construction to the loop-on-the-ground antenna, this transformer-fed radial field replacement was covered in an article in the October 2020 RadCom magazine (pages 44-45). Both home and portable set-ups are described in the article.
The loop on the ground counterpoise solution, as well as being easier to deploy also assists reception as when used the signals received have a lower background noise level.
73 Ed.
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Hi Matt, you could read that UNUN as a coax choke if you like: it does not function as an impedance transformer but to prevent the coax braid radiates so that only the antenna is part of the radiating system instead of the antenna plus coax.
Note the impedance is around 50 ohm for the bypassed coil (14 MHz) but you can expect the impedance goes down when the coil is active…
Consider as well that the sloping radial (being most part of it directly on ground) adds losses that helps increasing the impedance: as a result the SWR will be good and the transceiver “happy” but the performance is not 100% because part of the radiation is lost in the coupling with the soil.
That is correct: I had about 10m length in the wire winder and had to strecht about 1/4 wave length for the operating band. When on 7 MHz I used almost 10 m.
Bear in mind that a single radial creates a pattern less omnidirectional compared to 3 elevated radials, more like a pointed oval shape towards the single radial, but the difference is not that big (it is not a beam!).
I used the antenna without any intermediate antenna tuner, and had to enlarge / shorten the radial length a few times to put that in resonance (or lowest SWR) being more or less repeteable.
Good luck in your experiments
73 Ignacio
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I expect the on the ground radials as suggested by others in the thread is likely the main source of your variance.
But I once made a loaded vertical with raised counterpoise (or is it a single radial?) a la @MM0FMF. Was getting very confused trying to tune it when I first built it, until the penny dropped that the carbon pole was having an impact. ie as the vertical element moved around in the wind relative to the pole it was changing resonance. So if your pole is very carbon-y, and hence conductive, in my experience it may have an impact.
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Buy a Slidewinder DX, gets me contacts in North and South America
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Except they seem to be out of stock or discontinued and cost about £200 more than making one yourself.
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And they’re big, heavy and expensive too.
Back to Matt’s frustration. My experience is you can make nominally centre loaded verticals repeatable and tame if and only if you keep the radials off the ground.
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So you are saying you can make this antenna for nothing? Because the Slidewinder DX is £168 and, they are not out of stock, although you can buy the coil separately and source all the other bits yourself,
I have never had any problems carrying mine in my rucsac, in fact, I’ve used it with a G90 on Gun
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No, I don’t mean this exact antenna. It just seems a lot of money when you can easily make antennas yourself for a few quid. And it’s more satisfying when you have made it yourself. And 1.3kg does sound quite heavy.
All antennas can be considered some kind of dipole. In this case one side is only 5m long. At 40m you have made an ad hoc OCFD.
Have a look at Mosely’s verticals
You can see how long they are, and the radial lengths. e.g RV-4F (6.7m) or Trapmaster V-4-6 (6.3m)
On 40/60m your antenna is going to be very small, and thus, even when you get it matched up, low efficiency compared to the EFHW.
I think you are best keeping the EFHW, and just having a separate vertical for 20m up, eg a trapped vertical.
Consider the RV-3C. It is only 3.7m for 20,15,10 or this 3.4m one
My pole is 5.6m actual, so you can slope the radials down as guys from ~2m
Note: The Mosley traps are aluminium tubes with two traps, and the tube is acting as the element between two traps. The traps use capacitance between the outer sleeve and the inner element as the traps C.
Hi Ingo,
thanks for the link to that article, which is apparently written by the proprietor of STEPPIR antennas. It makes a lot of sense. The entire article is not only readable but is consistent with experimental data found by not only me, but many others. I think it contains very good advice on the radial subject.
Recommended reading!
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Hej Matt,
I must admit I stopped reading the thread after Andrew VK1DA’s posts to which I absolutely agree. Maybe you want to know what vertical I use and which I used for our portable-2-portable QSO on 20th April.
I designed her for the 2015 SOTA 10 m challenge when I wanted some DX’ish antenna for that band. She’s basically a 5/8 lambda radiator over three counterpoises which I usually feed at roughly 2 m above ground level. All counterpoises slope down to 1.4 m which is the maximum length of my walking poles. 
So I took a piece of antenna wire (6.2 m) and also made a loading coil for 10 m resonance.
A simple L-match makes the antenna multiband 14, 18, 21, 28 MHz. 24 MHz would be close to halfwave resonance, so it obviously does not work there. Each counterpoise has a link to vary their lengths. A current choke / 1:1 balun is needed at the feedpoint, e.g. ferrite core of mat 43.
I close the coil switch for operation on 14 and 18 MHz, on 21 and 28 the switch stays open.
Don’t ask me which counterpoise length I use on each band, I just can’t remember. If I can’t tune her, I just open/close all links. I was always able to tune, regardless of the summit I was on.
I also tried to make the antenna work on 7 MHz, which needed an additional loading coil (a larger coil with another switch didn’t fit in the small housing) and another switch which connects the capacitor either before or after the loading coil. It seemed to work which means I was able to tune the antenna and I had some QSOs on 40 m. But the linked dipole performed better for inter-euro QSOs and 40 m would not be the band of my choice for SOTA DX. So I abandoned the plan to use her on 7 MHz on a regular basis.
Ahoi
Pom
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Hi Takeo,
good idea. Will give it a try with 8 radials and will write about the experience a bit later.
Thanks
73
Ingo
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