Tim,
Stick with the high single radial. Height is your friend, always. By pointing it in your preferred direction you are getting a bit of gain thataways albeit with a reduction in the opposite direction.
Yes it is more closely related to a dipole than a ground plane but it’s working AOK.
For 10 m I am using a flowerpot type half wave vertical. Simple. Functional. Unidirectional. Small footprint. No ATU.
The downside is it is mono band and had no gain.
73
Ron
VK3AFW
Monoband is fine with that one as it is pretty quick to deploy and then replace with something else.
I’m thinking of a linked 12m/10m EFHW that I could use with my existing auto-transformer and run vertically up a 6m or 7m mast. Will be a simple build. Anyone done this?
Despite reading articles and searching the internet (on more than one occasion) I can’t find consistent definitions for ‘radial’ and ‘counterpoise’ and the distinction between them if any. Many of the sources contradict each other leaving me bewildered. One says they are the same thing; others imply they’re different.
I think the three short metal rods on the base of my V2000 6/2/0.7m colinear are radials because a) Yaesu call them that, b) they are a ‘tuned’ length (one of them is for 6m and is much longer than the other two), and c) the radials are ‘raised’ (about 5m from the ground).
I think the two ~7m-long wires I lay out on a rocky summit and attach to the ground spike of my MPAS Lite vertical are counterpoises because a) Chameleon call them that, b) they’re not a tuned length but (apparently) act as a capacitive connection with the ground below (the latter being the other ‘pole’ for my 17-ft monopole whip), and c) they are not ‘raised’ by much (well, only by a cm or two).
Any antenna grounding experts, feel free to un-bewilder me or point to some reliable resource.
BTW: I don’t understand why anyone would spend the time and effort to raise two or more wire radials off the ground for a temporary portable antenna particularly in wintry weather. It would seem less effort (and probably gain more performance) to erect a centre-fed dipole (e.g. inverted V).
Andy, Your BTW is an interesting point. In winter (specifically wintry weather) you probably only want to put one wire up. With all of the 10m activity this year, that could be a monoband. Likely to be vertical because of the short lengths involved. You get your points, hopefully some 10m challenge new ones and almost certainly some DX.
Personally and because of my knowledge of GM/ES summits, having been fortunate enough to climb them all, I would consider antenna type based on the type of summit (in wintry weather). A shelter with a trig in the middle is screaming out for a dipole, supported by a mast strapped to the trig. That way, everything apart from the antenna ends are inside. The downside is un-doing links to change band. Or do I just need to build a 10m one, to live up to my statement in the previous paragraph? Probably. Some summits suit an EFHW/EFRW/W3EDP and coax because of nearby fence posts or trigs some distance from shelters.
However, you may have seen in my recent report that running an EFHW 3m up a pole as a vertical and sloping away from the cairn achieved the same result (operator comfort, simple to erect) and allowed more bands to be enjoyed, with DX on three of them.
The monoband (with radials) and gain antennas that may be more time consuming and difficult (in wintry weather) to erect may not be needed at this time of high SFI.
Ultimately the question is, as always, what do you want to get out of your activation?
Hi Fraser, perhaps you activate at some very remote summits and are undisturbed by other walkers during your activation but I find, even when I think no one else will show up at summits I do (mainly G/LD and G/NP), someone does and wants to stand at / sit next to / touch / have lunch at / take photos of / the trig point so I avoid even sitting there not alone tie my antenna pole to it.
Re doing 10m only during adverse weather, I’ve done that (because my fingers got too cold to paddle any longer) but I feel bad if I don’t also do 30m so that regional and EU chasers can ‘bag’ the summit too. As I said at post #35 above, that’s why I chose to use my MPAS Lite vertical and got 8 (mainly N/A) 10m contacts in 9 mins and then 13 (mainly EU/UK) 30m contacts in 14 minutes. That’s about as long as I can take sitting on a sub-zero un-sheltered summit albeit wearing 5 top layers.
Very good point. I rarely see anyone.
Yes, me too if I don’t do 40m. Some of those chasers have helped me get my 4th contact on many an occasion. Sometimes I’ll only take VHF gear with me (if I know I can make it work) and I don’t have the same guilt trip.
Yes. Originally a counterpoise was the name given to an alternative to an earth connection. I always consider a radial a form of counterpoise.
However, when it doubt ask Kraus. Counterpoise Systems There is probably something on Rothhammels Antenna Book but I only have a German PDF of that and have not delved deeply.
Normally because they have perfected an almost zero effort way to doing so. I find old broken wooden tent poles with metal tips make ideal distant supports for about 1m AGL. Frozen ground is an issue of course.
Yup… I review what I think the ground will be like and choose antennas that will be deployable even if some other antennas may be better for the propagation.
My 1st EFHW was for 10m, so just 5m long. As I didn’t have the right toriodery stuff in the shack at the time I made an AA5TB match which would let you tune the 5m long wire to be 50Ohms on also 12 and 15m. It worked well in that I was able to work US chasers from GM summits.
As much as possible. Ah but then realism creeps in and I match the activation to the WX and summit. Hence little 13cms in deep Winter when doing up SMA connectors is so very difficult.
The fun part is every POTA or SOTA activation is different.
I have a vertical with 4 ten foot wires, another uses 4 32 ft wires and one that uses a raised elevated wire. I make contacts with each no problem but I have been sad when I missed completing the activation.
Not enough power, poor antenna choice or not enough sunspots
John VE3IPS
SOTA in a refugee location,? Buddihex Beam of course
Mount Everest? The North Face Denali vertical with 10 ft wires
A park? A inverted vee on a mast
Chameleon MPAS 2.0…not hiking too far
Wires = counterpoise = radial = the other half of a vertical
Hi Andy
Lets build a GP antenna and start with imagine a vertical dipole in free space and feed in the middle. Field lines of electrical field are starting rectangular from the surface of one half of the dipole end ending rectangular on the other half. On the way they are bent. In the horizontal plane through the middle of the dipole all these field lines are rectangular to this plane. Now put a large metal plate in this plane. It doesn’t effect the electrical field (rectangular).
Now remove the lower part of the dipole and feed between metal plate and remaining half of the dipole. The metal plate didn’t radiate. You have a monopole, a GP antenna, a radiating monopole over a GROUND PLANE.
Now important: along the field lines there is a so-called displacement current (established by Maxwell). On points this displacement current is touching a conductor it is continued by a “normal” (convection) electrical current. All the current through the field from the monopole is flowing through the metal plate to the feed point (or back). All the losses on this way are reducing the efficiency.
It’s possible to reduce the metal plate to some wires mounted RADIAL to the feed point. (As more as better up to a saturation.) The effect to the electrical field is nearly the same. For most cases (in SOTA) 3 or 4 radials are enough, 2 are possible.
The metal plate/ the alternate wires don’t radiate, only the monopole is radiating. If you use only one horizontal wire (one “elevated radial”) this wire is also radiating. You have again a dipole (in a special configuration). If this wire is close to the ground (earth) much of the radiated energy is consumed by the ground. This is the reason for elevated mounting.
A L/4 monopole shows a low impedance at the feeding point, the current is high. Low resistance in the metal plate (in the radials) is important. A L/2 monopole shows a high impedance, losses in the GROUND PLANE are less important. This is the advantage of HW (or n * HW).
If you feed an antenna, you have to drive a current in to the antenna. Connecting your generator only to the monopole allows no current. You need a second connection. This is the counterpoise (like Andy wrote). In some cases the counterpoise should have a low resistance and in some it’s not so important. (And the “resistance” of the counterpoise contains also the coupling to the environment.)
Sorry if I preached to the converted.
73 Ludwig
Thank you Ludwig for your description. I agree with most of it. You speak of a ground plane but don’t link it directly to the word ‘counterpoise’ (which I think is an example of a GP). So, I’ll summarize what I believe is the distinction between radials and counterpoise wires.
As before, I welcome antenna experts to correct or add to this description.
Radial(s)
Form the other ‘pole’ for a monopole vertical to create a (compromised) dipole. I read contradictory information as to whether or not the radials themselves radiate. IMHO they appear to be connected to one side of the transmission line (e.g. coax feeder) so are ‘driven’ elements. So, I conclude they do radiate albeit less effectively than the resonant monopole.
Like all dipoles, no ground connection is needed (dipoles work perfectly in free space).
As one half of a dipole, you want them to radiate RF energy. Therefore, they should have a ‘tuned’ length e.g. 1/4 wavelength and raised as high as practical to avoid RF being absorbed by the ground.
A large number of short radials (e.g. 8 at λ/8) is more effective than a small number of longer ones (e.g. 4 at λ/4) but up to a point (somewhere between 16 and 32 radials where it’s diminishing returns).
And if the antenna is multi-band, you will want to include some radials with lengths tuned for each band (like my tri-bander colinear mentioned above).
Counterpoise wire(s)
Form a (compromised) ground plane for a monopole vertical. The GP reflects the radio waves radiated downward by the monopole. It’s not itself a ‘driven’ element [a GP acts like a mirror but at radio frequencies]. The GP provides a ‘return’ path [or completing the circuit] for the RF current (the current is AC so the direction alternates).
Used where soil resistance is high (e.g rocky summits) and where a good ground connection cannot be made. As the DC connection to the earth is poor, the counterpoise functions as one plate of a large capacitor with the conductive layers of the earth acting as the other plate.
The exact length of the CP wires is not important but is related to wavelength. I’ve seen recommended lengths in the range λ/4 to λ/5. A large number of short CP wires is more effective than a small number of long wires.
I wonder if the contradictory statements from different sources is due to their authors using the terms radial and counterpoise interchangeably. In any case, the one thing I’m certain of is that this topic is one of the least well understood among the amateur radio community.
The great Ivor Catt had lots to say about displacement current. None of it good.
Andy,
Radials are wires that run out from the base of a radiator, like radii of a circle. They are around 0.25 wavelength long if in the air.
A counterpoise, or counterweight balances up the antenna to present a workable impedance. It is usually a single wire. For example an 85 ft radiator often is paired with a 17 ft counterpoise. It’s coincidentally 3/2 halfwaves on 20 m.
In the old days broadcast band transmitters often used a steel lattice mast on top of a building and an adjacent bed of parallel wires to form a counterpoise. An ATU was required.
Other Andy
Displacement current? OMG. Oh yes there was that LPA mini mf antenna scam in which it was mentioned. I was intrigued until I read that in its theory.
Put them in the same box as radio active tips on lightning rods and warm fusion and water is a gel theory.
EDIT. Reference to the UK removed.
Here’s how the propagation patterns look for that setup (modelled over “good soil”):
And here are the propagation patterns for that setup:
Not a great deal of difference but, yes, there’s a little more directionality with the second.
Soil conditions play a small role in the elevation propagation, with increasingly poor soils increasing the null in the backwards lobe, while not affecting the forwards lobe to any discernible degree.
One reason might be to achieve better propagation, but I’m just guessing. Here are three examples of an antenna like that used by Tim M7TSU - albeit with a base at 2.5m instead of 3m agl - with one, two and three radials at 30° to the horizontal (adding more than 3 makes very little further difference):
…which would seem to indicate that the effort of raising 2 or more radials off the ground would pay definite dividends to “the more active type”, especially if, say, three radials were to “double up” as tensioning cords for the GF mast. YMMV, as always…
Incidentally, lengthening or shortening the radials from the “standard” 0.25λ has little effect on the propagation patterns, but does alter the VSWR since one is effectively lengthening or shortening the antenna as a whole. Some example numbers from a 3-radial model (actual values in the field would, of course, differ from these as the objective conditions vary):
| Radials length | VSWR min. freq. |
|---|---|
| 0.200λ | > 30 MHz |
| 0.225λ | 29.6 MHz |
| 0.250λ | 28.9 MHz |
| 0.275λ | 28.2 MHz |
| 0.300λ | < 28 MHz |
Rob
[Wiki says] The gains […] are only achieved if the antenna is mounted over a perfectly conducting infinite ground plane. With typical artificial ground planes smaller than several wavelengths, the gain will be 1 to 3 dBi lower, because some of the horizontal radiated power will diffract around the plane edge into the lower half space, where it dissipates in the soil
My point was for a temporary antenna installation at a SOTA summit, [and notwithstanding @MM0FMF 's impossible-to-achieve “zero effort” comment] the time and effort spent deploying many raised verticals (on extra poles needed to be carried) is unlikely to have greater gain (in practise) compare to a centre-fed dipole, which we all know is pretty quick to deploy. The vertical does have the benefit of being omnidirectional but I’ve never found the radiation patterns of CF dipoles or EFHWs to be a drawback.
I would agree with that statement, providing that the dipole is set up as an inverted-vee to provide a more isotropic azimuthal pattern, resulting also in an input impedance close to 50ohm, and would add that a linked dipole would also provide more bands than the monoband vertical.
I hasten to add that, due to a perennially-bad back, ANY deployment of ANY antenna type is for me a major effort. Quick in deployment they ain’t when I’m on the hill.
Also, your Wiki quote does not compare apples to apples, whereas the several vertical models used in my examples above do do this.
If I had to lay out a ground based radial(s) I would have to attach them to the system at the pole and walk out over the terrain unwinding the wire and laying it on the ground. It will take some time, X secs.
For an elevated radial/counterpoise I have to do all the above. I have an old tent pole which is two sections each about 50cm long. There is elastic up the middle. When you get to the end you unfold the sections and the elastic pulls the two sections into a metal couple. One end is reinforced, locate that end and push it into ground. Attach radial/counter poise to top of tent pole about 1m +/- off the ground. Deployment is X secs to unwind the wire and Y secs to push in the tent pole and attach the wire. Y secs is of the order of 30-60secs. So elevating it is not a huge amount of time. Of course, rocks, lava, frozen ground make this very much harder so as I normally have some clue what the ground will be like, if these are likely some other plan is put in to use.
I posted on here what commercial HF users are using for 1/4wave GP radials and TBH it’s not really much more than the typical SOTA 1/4 on a pole with 3 sloping radials.
Rob, I’m not clear what sets of apples you are comparing.
My point was about comparing the time and effort (when using raised radials) and not about comparing relative performances of I-V dipole vs monopole vertical. I already said earlier in this topic that I couldn’t tell the difference in actual performance between my 40/20/10 EFHW Inv-L and MPAS vertical on 10m in recent activations. That was based on reports given/received, which is more important than hypothetical models. I’m not anti models. I created and used models extensively in my professional life as a R&D electronics engineer and am only too aware of their limitations due to real-world factors not included in them.
Andy, that’s for one raised radial. So, for N radials that’s N old tent poles to carry in your rucksack and total deployment time N x (X + Y).
Andy, if I’m reading it correctly, the Wiki article quotes figures of gain which are comparisons of an actual (or modelled) antenna with a theoretical antenna type, usually an isotropic radiator (ain’t no such animal), or a straight dipole in free space (ditto…), so it’s an apple compared to an orange. So, that’s great for gains, but the gain figure gives no indication of propagation pattern. Comparing propagation patterns between very similar configurations of basically the same antenna is (mostly) apples to apples.
Again, I’d agree with both your statements and sentiments regarding the various aspects of antenna design (I’m not an expert!) and practice, and about limitations of modelling. At the end of the day, how an antenna performs on the summit is really the only consideration worth talking about.
Yes. But how many radials do you have? 3 elevated would add 3mins to the setup. I spend longer than that standing around scratching my bum and looking at the view when I first get to the top.
The argument is not that it doesn’t take time but that effort can be effectively minimised to not worth worrying about.
