It’s not the physical effort, it’s mainly the time taken to deploy the antenna system (which - for me at my age in winter - is important to minimize) and the faffing about (often with gloves off) with bits and pieces.
I also like to minimize the number of components involved which is proportional to the likelihood of one breaking on-site, being lost in the grass or left at home.
That’s what I like about my Cha MPAS Lite vertical. Yes, it’s expensive but it’s robust, simple and quick to deploy, has a smaller footprint (good for busy summits) and despite not being as efficient as CF dipoles does the business on 30m to 6m (band changing without having to lower the IV partially so I can reach the links). e.g the N/A 10m contacts I got on Wednesday (see post #35 above).
My acid test for the antenna is: Are my fingers frozen even before I go on air ?
Anyway, this is all summit/weather/band conditions/effort in getting there, and as I said before, what you want to get out of the activation, specific.
On a rocky summit you might just as well lay the radials on the ground - have a weight on the end and chuck them out. The rock conductivity will be negligable in most cases depending on rock type. On a heathery summit lay them on top of the heather, as above just chuck them. Its when you have a nice surface of turf - particularly if it overlies peat -that you need to take care.
Yes I know, there was / is any development about this topic.
There is an effect of electric flow in non conductive environment (e. g. capacitor). More than 150 years ago a mathematical model was developed to calculate this effect of flow using voltage (electrical field strength) and current (displacement current) AND an explanation was made how it works tangible. The model was used by Maxwell to predict electromagnetic waves (Maxwell equations) around 20 years before the experimental proof. Much time later the tangible explanation for the effect found to be wrong. But the model was widely independent from the specific explanation and was usable furthermore.
Hi Ron
its a different box.
In the end: for many cases the imagination of a displacement current through a non conductor as a pedant for a current through a conductor (each could be a continuation of the other) is fine to understand the situation.
It’s been 50 years since I studied Maxwell’s equations as a Physics undergraduate. A few years ago - whilst waiting in the departure queue for a Ryan Air flight - I saw a bloke close by me in the zigzag queue wearing a tee-shirt with Maxwell’s equations on the front. We had a fun conversation as the queue edged forwards. I can still explain them at a superficial level but long ago forgot how to use them.
If you haven’t already done so I suggest you read the topic “Displacement Current” on Wikipedia. It explains where it came from and points out it does not exist. Maybe you are familiar with it already.
I would be concerned about any analysis that depends on displacement current to work. I don’t need to imagine a fictitious current flowing through a capacitor. But if it helps you I am happy for you.
Maxwell believed there was an Aether. AC currents weren’t known nor was the electron known until decades later. Maxwell invented Displacement Current so his equations looked balanced.
The combined brilliance of Maxwell, Hertz and Marconi made our hobby possible.
For that alone we can accept errors they made on the basis that overall they made gigantic leaps forward.
I keep changing my mind on my personal trade-off of performance vs deployment time of the artificial ground for my Chameleon MPAS Lite vertical.
I’ve read that a large number of short counterpoise wires improves the gain [or really, reduce the losses] of a ground-mounted λ/4 monopole vertical more than fewer wires with longer lengths.
This clip of a graph (from an article by Mike Mertel K7IR, Radial Systems for Elevated and Ground Mounted Vertical Antennas) shows that when using 4 ground-mounting CP wires, the gain plateaus for lengths longer than ~0.1 λ.
With the 60’ (18.2m) length of CP wire Cha supplied with the MPAS I already divided it last year to make two ~9m length CP wires. Dividing them gives me 4 ~4.5m length wires, good for the lowest frequency band I use with this vertical, 40m.
The ground spike goes through the carabiner which, with the 3 plastic O rings, provides strain relief on the solder-tag type connections to the spike (under red knob) should someone yank or trip on one of the CP wires.
The new arrangement has the same weight and packed volume as before but will take slightly longer to throw out on the ground in a radial pattern. Unwinding multiple wires from the single plastic winder can lead to entanglement. Fortunately, this wire is a lot thicker than the UltraLite I use for wire antennas. I going to experiment with winding/unwinding one pair ‘figure of eight’ and the other pair ‘straight’.
It will be interesting to see if this modification has any noticeable difference to performance especially on the lower HF bands.
Last year I went though exactly the same thoughts Andy with my MPAS Lite. I’m quite happy with my current version which uses 8 x 3.75m of 22awg PTFE covered wire (a lucky eBay find) arranged into 4 pairs. I use 2mm bullet connectors to allow me to connect less wires if I need a faster deployment (i.e when its raining!) and also provides a quick break if tangled/tripped over:
The pairs of wires have the corresponding bullet connector on one end and loops on the other end that slip over the ‘prongs’ on the wire winder. This makes it fast to wind and they don’t end up in a tangled mess on the winder:
So I can deploy up to 30m total length and they are short enough that its more of a ‘throw it out’ action than lots of walking back and forth. The total weight of the radials including the winder is ~230g which I’m happy with given the flexibility it offers. I’ve also replaced the feeder with 5m of RG174 including a choke:
I’m sure folks might wonder why buy an expensive antenna and then spend time remaking parts of it. Well in my defense I bought it when I came back to ham radio and wasn’t sure what I wanted to do, but having said that I won’t be getting rid of the MPAS Lite because it has never let me down. Its become my bad weather antenna - I’ve used it in high winds, pouring rain and always got the SOTA or POTA activation done. It also doesn’t need a lot of real estate to deploy (especially with the multiple short wires) and is fairly low profile. Although I did get a couple of locals on a Norfolk beach last year who were convinced I was sat in the rain communicating with Russian submarines
I’ll be interested to hear what your thoughts are after using the new configuration.
For the 40-10 m bands I use 3 short radials of 3.5 m length, which I arrange with bamboo poles at about 30 cm above the ground. More radials or longer radials offer hardly any advantage.
It’s what I’ve learned over the years. Below is something I posted a few years back about commercial 1/4wave antennas and shows that professionals stop at 9 radials in their case.
More than 3 radials makes sense, of course, but only if they are not elevated. But for the same power of 3 elevated radials, you have to put quite a few radials on the ground.
I agree with this. Radials (raised, tuned length) form the missing lower pole for your monopole vertical. If the antenna is high off the ground (like my VHF collinear) the radials should be sloping down to counteract the lowering of impedance.
Ground-hugging wires are a counterpoise - an artificial ground - and behave differently. Ideally, you want a large metal plate as the Ground Plane. Failing that, as many wires N as you can be bothered with (see the graph in my previous post). For me, the ‘faff factor’ N=4.
Interestingly some are now using Faraday cloth* as a ground-plane/counterpoise for HF vertical antennas. I have tried it with my tripod mounted loaded vertical but I go back to the 8 x 3m wires each time.
*Faraday cloth is being sold all over the Internet for those who wish to shield their smartphones from intrusion or from being tracked. No signals in or out means no GPS recorded location - but of course also no calls!
73 Ed.
the elevated radial graph in the article by N6LF is based on NEC modelling. Which is correct, in theory.
In the real world when you use a small number ( 4 or less) elevated radials which are near the ground, you can get very uneven currents in the radials. The real world ground is not uniform, so the individual radials couple differently to the ground. 1 or 2 radials typically have the majority of the current flowing, others with very little current. If the current is not flowing in the radial, its flowing in the lossy ground.
For a long time my 160m inverted L had elevated radials at 2 - 3m over the ground, in the woods. I started with 6, added a couple more then ended up with 12 in total. I have a homebrew clamp on RF ammeter and was able to do experiments and look at the currents with different numbers of radials connected. All the data is in my notebook, in one case a certain 2 radials at 180 degrees to each other show 225mA in one radial, only 30mA in the other! Thats with all the other radials disconnected and 50w carrier.
With 8 radials connected the currents become quite even, with all 12 radials connected they all looked the same with between 40 and 50mA in each radial. Radial current total with 12 radials 530mA, 2 radials 255mA. The missing current is in the ground! Not a big issue if you have excellent ground below the radials, even better salt water.
These experiments and a lot of exchanges were shared the John ON4UN (SK) when he was writing the last edition of Low band Dxing, they tied in with other data he had included in that chapter.
For the original post about 10m, it does make a difference keeping your elevated radials 1 or 2m above ground if you can. 1 radial wont make your vertical into a magic beam, it just skews the pattern and you loose out in total.
73 Gavin
GM0GAV
PS pictures from 2010 of my 160m Inverted L I am taking about. Big coaxial choke round pole, the box has an L network and you can just pick out all the radials and the radiator wire heading skyward. A top performer until the 30m high tree was blown down
I QSY’d to 10m on my EFHW after working 40m, as I wanted to be quick. I made some contacts, two in NY but I felt that I had such a difficult time I even went and checked that band conditions to be sure 10m was still cooking….
So I put up the 1/4 vertical with a single radial on a pole at a sloppy angle. (I was trying to be quick and beat darkness)
Suddenly I could hear California and @F4WBN, (who’s technically in my skip zone) was kind enough to contact me again and let me know how much better my signal was. It was a huge improvement.
10m 1/4m vertical is always in my bag right now….my favourite antenna in these conditions.
Probably benefiting from the lower takeoff angle of your vertical. Interesting you were still making N/A contacts until about 1720utc. Sunset was ~1710 at your location today. So, that’s consistent with the 10m WSPR tests I did recently which showed that 10m contacts followed the MUF which rose rapidly above 28MHz after dawn and dropped rapidly below 28MHz after sunset. As predicted then, the 10m EU-NA window is widening as the days get longer albeit that other factors remain the same.
thanks for your comment and sorry for my delayed answer.
Yes, you are right and so we shouldn’t believe in radio waves!
There are two things: an electric flow D AND an old explanation how it works tangible. Later the old explanation was found to be wrong but the flow D (called “displacement” or “displacement current” or “displacement current density” or “displacement density”) is accepted until today. Following Maxwells equations without D no em waves could exist.
D goes along the electric field. Imagine this field you will get an imagine of the displacement. There is a continuity between displacement and electric current (see e.g. Wikipedia). From “points” where D is touching an electric conductor an electric current is starting through the conductor. IMHO this helps to understand the currents in parts of antenna systems, e.g. in radials or one “radial”.
Hi Ludwig, yes, it makes the equations consistent but it’s just an analogy (which - as you suggest - helps with interpretation of how electrical circuits work). But it’s still not clear to me whether or not you believe it is real.
Of course Maxwell predated quantum theory so today we should be talking about the creation of RF photons at the activator’s antenna and their annihilation at the chaser’s antenna (or vice versa).
And if you believe the Many Paths theory [which I used to teach to A Level Physics school students] some of those photons will go via any paths in the universe including going to Pluto and spelling out the word SOTA on the way back.
Pendants will point out that actually there will be many intermediate photon absorption-creation’s in the ionosphere.
