A 6m beam for portable operations

There is always a need for another antenna. If this does not sound like a self evident truth you are probably reading the wrong blog.

For a while I had been contemplating building a new 6m beam. I have the DK7ZB multiband beam for 2-4-6 meters. When I made it, I thought it would be a nice addition covering these three bands. In practice however I found I don't really use the 2m and 4m bands and therefore have an overly complex antenna with 7 elements while only using it as a 2 element 6m beam. To make it transportable I have to remove (parts of) the 4m and 6m elements. With the 2m elements the antenna is rather bulky to transport.

I was looking for an antenna for 6m with more gain but less complexity in assembly and one that would be easy to transport. One of the things I wanted to avoid was having to use bolts and (wing)nuts to attach the elements - as these small parts have a tendency to go lost when you drop them while out in the field.

My ideal "high gain but still transportable" option came down to a 4 element antenna with a boom of 4m. Split in two the boom is transportable. The same goes for the elements. Now all I needed was a way to attach the elements without using any loose parts.

I remembered an old 11m vertical that had radials you could screw into the base. What if I could make some construction to be able to screw the elements in position?

Keeping the antenna light (it is for portable operation) I chose 8mm diameter tubes for the elements. The inner diameter of this tube fits 6mm metric threaded rod. Glueing these in I had my threaded elements. 

Now for the other side I looked at a threaded rod extension (coupler). There is a round version and with the 6mm threads it snugly fits in a 12mm diameter aluminum tube. 

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With this concept working I continued developing the antenna by spacing the elements along the boom (using plastic element holders to attach the elements to the top of the boom) and making them to size.

For the dipole I used a plastic pipe to create a mechanical non conducting connection. I inserted the same threaded rod extensions I used for the other elements. In this case I soldered a piece of wire to the extensions - creating a connection point for the coax.

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I then created the quarter wave impedance transformer as specified by DK7ZB and put all the pieces in a small junction box. Note that I cut out an opening in the bottom of the junction box to be able to use an element holder for the dipole. That way I know all the elements are nicely in parallel.

In the end there is one spot left where this antenna has bolts and wing nuts: at the point the two boom parts meet. Perhaps I can design some other solution there in the next version.

Time will tell if the threaded connection is an improvement or that it will drive me crazy when dirt gets on the threads (quite imaginable in the field). For now I like the compact package the antenna constitutes while disassembled and I like the way I can quickly put it together.

After completing construction work I took the antenna out for a test. The results were peculiar to say the least. The VNA showed readings that were off and over the air tests did not correspond to the theoretical performance of the antenna.

Reacting to my first post about these results, Enno PF5X pointed out that not all glues are created equally. I used metal glue but did not take notice of the conductivity. Testing it afterwards I found issues with the conductivity on several elements.

Added metal screws to ensure a good conductivity

So I made a necessary change to the design: connecting the aluminium tubes and the inserts (the threaded rod and threaded rod extension) with metal screws.

You could argue that the whole gluing step can be skipped in this final design but I think it makes for a more robust construction - which is important for an antenna used portably.

With this new antenna I went out last Saturday as the IARU 50Mhz contest was on. I also took my 2 element beam (actually a triband beam with 2 elements on 6m) for comparison.

PE5TT was available (again) for a simple test. At 25km distance with a comparable antenna we had the same signals both ways but s9+ this time (with design v1 it was only s7). Decreasing the power to 10w we could establish that the new beam has 2 s-points gain over the 2 element beam. We also found the F/B was at least 4 s-points. F/S was even more dramatic.

I subsequently entered the contest. There was some Es but most of it was too far south with weak skip to G. However I was able to check the beam's characteristics switching between the two antenna's. Confirming the 2 s-points difference. And even though signals vary strongly during Es conditions the practical F/B performance was apparent as even the strongest stations from S-Europe almost disappeared once I turned the beam to G.

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Building a new lithium battery

For years I have been using lithium batteries to power my radio equipment when portable, both LiPo and LiFePO4.

If you want to know more about these different types read this post I wrote a few years ago.

I started out buying batteries from HobbyKing in China. Then I decided to build a few myself with pouch cells I bought from AliExpress. 

Recently I lost two LiPo pouch cells when I abused a battery - forgetting to attach the under voltage alarm. Another LiPo cell of a different pack turned out dead without a clear cause. I ordered a new cell but they are quite expensive. Losing three of those cells in a short period of time I suspect I might have to replace more in the future. So I started looking for other solutions with cheaper building blocks: smaller cells.

LiPo cell after abuse

Looking at smaller cells I first stumbled upon the 18650. A popular Li-Ion battery and quite small but you need a lot of them to get a useful capacity as they are around 2Ah a piece. However I found more practical LiFePO4 cells with a 7Ah capacity: 32700. I bought a set of those with strips of nickel attached to the ends for soldering as I do not have a spot welder (yet).

The voltage of four of these LiFePO4 cells is too low for my amp - that is why I opted for LiPo up till now - but as the amp is designed to handle up to 18V a battery of 5 cells would do the job. So I decided to go for a 5s3p design (5 cells in series and 3 in parallel).

Building a 5s3p battery

I bought a BMS as well with the idea that it will protect the battery from under voltage. And it allows me to charge the battery even with a simple (non balancing) charger. I was hoping that a BMS is more effective in balancing than the chargers I have - that take quite some time to balance an unbalanced pack.

Completed battery with BMS

Testing the battery my first lesson was that you cannot charge a battery that has a BMS with a smart charger. The BMS starts kicking in when the first cell approaches its maximum. The charger notices the increasing resistance and shuts down with an error ("connection break"). 

Charging through the BMS with a smart charger 

Time for Plan B I used a 12V source and a step up converter to 18V to act as a "dumb" charger. Meanwhile I checked the charging current and the voltage of the individual cells to see what was happening. 

This time the charger patiently waited for the BMS to allow for a current to run. The BMS would drain the cells for a bit and then allow a charge current until one of the cells hit around 3.5V and then the cycle repeated. However it did not seem to be able to bring the cells closer together. After an hour there was still a spread of 0.2V between the cells. 

After letting the pack sit for a while I found out that the BMS aims to keep the cells at around 3.4V (on my V-meter). So during charging - aiming for 3.6V - a cell might go higher but the BMS will continue to discharge it until it is back at 3.4V again.

I will have to see if this noticeably impacts the capacity of this battery pack. When I have some more time on my hands I will run some tests and see how it behaves under the stress of powering a 400w amp.

Update May 2021:

After using the battery pack for a while I decided to remove the BMS. In my situation - having balancing chargers - the BMS only adds complexity.

The second thing I noticed is that the pack was struggling delivering the high amperage the ALS-500m pulls. Testing the pack at home with a dummy load I saw the nickel tabs I used to solder the main + and - wires to became hot, red hot even. 

So I decided to solder wires to the first and last set of (three) parallel batteries to spread the current. Testing that thoroughly I found it to work perfectly. All cells now discharge evenly, even under high load.

Shrink wrapped end result (with built-in Voltmeter)

C-pole tuning part 3

This weekend I went out to test my C-pole with a new 1:1 balun. As I blogged before I ran into trouble with this antenna and the common mode choke I constructed in W2DU style.

To rule out any balun influences I had decided to tune the C-pole last week using my VNA without any balun present. My idea at the time was that this would give me the most clean picture of the antenna and would rule out any failure of the balun ruining the tuning process. Smart move? No. (but I learned something).

While working on the "naked" antenna I was amazed how much off it was. To me at the time it seemed strange (I tuned it before didn't I?) but it did explain why it failed in operation. So I continued re-tuning the antenna - moving the feedpoint a considerable bit along the one leg of the folded dipole (basically the C-pole is a dipole with the ends folded in a square shape towards each other).

After 1,5-2h of pushing the antenna up and down again I had a perfect match in the 40m band. One happy camper.

At home I tested and optimised my 40m balun. Ready for the final assembly and testing.

This weekend I had some time to go out to bring it all together and enjoy the fruits of my labour. However when I set up the antenna with balun I found.... it was way off. Go figure.

Tuning the C-pole yet another time

Discussing this with my YNOMY team members we came to the conclusion that the common mode current - considerable in this design - influences the measurements of the VNA. So tuning the "naked" antenna was a stupid idea and the time spent tuning was actually time spent detuning it.

A frustrated ham is never going to be the best person to work on any project but I did decide there and then to re-tune the antenna one more time. I was almost finished when I too hastily bumped the VNA against the pole. The center conductor of the SMA plug attached to the VNA broke off and is now securely in place in my VNA port - making it neither a female nor male connector (gender neutral - a modern concept). That concluded the tuning process for the time being.  

Gender neutral SMA connector

So now I have to replace the SMA connector on the VNA. That connector - I found - is soldered into place with lead free solder that I cannot remove with my soldering iron as it just does not heat up enough.
Luckily Marcel PG8M told me he both has the connectors and a proper soldering iron. So now I have to find the time to go over to his place and have him repair the damages (keeping a safe distance all the time of course).

Cooking on a choke

Out portable with my (relatively) new C-pole antenna last week I ran into trouble. After about 30 minutes signal levels dropped dramatically indicating something was wrong. I saw the SWR skyrocket.
Walking over to my c-pole I felt the common mode choke was boiling hot. So I changed antennas and continued my operation.

Back home I began my investigation in what went wrong. Immediately there were two suspects: the antenna (high swr for some reason) and the choke (too low choking impedance).

The antenna was fine when I used it the first time and I did not change anything in the mean time. So the choke seemed a more logical candidate. The purpose of the choke is to minimise the amount of common mode current that you will generate with an unbalanced antenna like the C-pole. If the choking impedance is too low however there will still be a considerable common mode current left that will generate heat in the choke.

W2DU style choke with ferroxcubes beads

On this latest homemade version of the c-pole I use a W2DU style choke that I constructed myself using a number of ferrite beads. The type and amount I used I based on the factsheet. On paper the choking impedance was OK but I can't remember if I really tested it. Checking it now I measured a whooping 400 Ohm of impedance - far too low to stop the CM current flow (I wonder if the heat impacted the ferrite?).

Removing turns of RG58 from two stacked FT240 toroids

On my first C-pole I used a different current choke, designed on the basis of the excellent information by the late G3TXQ. I used two FT240-43 ferrite toroids stacked with a couple of turns of RG58. It is bulkier and heaver though than a W2DU choke, that is why I changed it.
That toroid based choke also became very hot on my first c-pole but I later discovered the antenna itself had an issue - causing high swr - causing high voltages over the choke.

So I returned to this old choke - abandoned but not scrapped. I measured it and it had an interesting profile. It was particularly useful in the 80m band range (5k Ohm) but certainly not bad in the 40m range (2.5k Ohm).

Measurement #1 of the choking impedance and transmission loss on my balun

I decided to take it apart and remove one of the RG58 turns. As expected the choking maximum moved up. The profile now suited a 60m antenna perfectly while impedance was higher in the 40m band. After removing two more turns I got a maximum in the 40m band. The choking impedance is now more than 5k Ohm there. That should do the trick.

Measurement #2 after removing 3 turns of the coax

When I have the time I will go out /P with my C-pole to check it without a choke - just to be sure it still is resonant in the 40m band - and then add my old toroid based choke. 

One man set-up for the 26m Spiderbeam pole

In January of this year I received the Spiderbeam 26m HD fiberglas pole. It is the tallest they have and afaik the tallest you can get. Cool for low band antennas with little compromise.
I used it only a few times as I can normally get all the antennas I have on my 18m pole (or on my aluminum mast) and I simply did not have the time to build and test low band antennas.

When I did bring the mast out I was reminded of its size and weight - 2m when collapsed and an interesting 18kg. If you have a good support - like the one I build that I attach to my car, or some strong fixed pole you can tie the mast to - it is possible to set this up on your own. Otherwise you need more people. When we used it in the open field during the PACC, we need 3 people.

A few months ago I build a simple support system for my 18m pole that allowed me to set this mast up in the open field without any hassle. I have been using this more often and started to think if I could make something for the 26m mast as well. I wanted to use a bigger surface this time, but use a different structure because it would become too bulky if I just enlarged the 18m version.

Walking around in a DIY store I stumbled upon a flat roof vent. The inner diameter is just over 110mm allowing the 26m pole to slip through with the end cap on.

Now picture this thing pressed between 2 layers of wood with holes on each corner for stakes / pegs. I could just see this working. So I took this home and started working on the two layers of wood.

I chose plywood and cut two pieces approx 60 x 60 cm. I chose the bottom layer a bit thicker so I could sink the bolts I was going to use into the wood (and that way keep an even surface). In the picture you can see that I already cut a hole in the middle with the largest hole saw I have. That saw is only 83mm so I next I enlarged the hole.

Enlarger the center hole

The intermediate result - starts looking like what I had in mind

I added 4 bolts though both plywood layers and the metal, made 4 large holes (25mm diameter) near the corners and glued the two layers of wood together. Another thing I did (like with the 18m pole) is to add a fixed ring on the top of the lower segment of the 26m pole and add three guy rings to it.

(sunk) bolts through the wood and metal

Fixed guy rings

I finished the work yesterday, so today I could make good use of the brilliant weather we have at the moment to go out and see if my construction works.

Just for a comparison of size I put the 26m and 18m poles side by side with the two mast supports.

I then started setting up the 26m pole. I used four stakes in the corners of the plate I constructed. They were of different size and mostly too long as you can see. However, they still do the job.

As I hoped, the collapsed pole slipped in nicely and stayed upright - even before I guyed it. That is very convenient as it allows you to add the guy lines one by one and adjust the tension of each one until the pole is fixated and completely vertical. 

I then pushed the segments out with my 20m long end fed wire attached to the upper segment (while I was there I might as well make some contacts). I was lazy and only wanted to assess if my idea worked so I did not guy the pole on any other level. 

As you can see the pole was not completely vertical. This was due to a lack of tension in the guy lines (will put on more tension next time) and of course due to the lack of guy lines higher up. It stayed up though and I was able to make a couple of WWFF contacts in the half hour I was there.

It is easy to set up and break down the way it works now, so I am pleased. The one thing I do need to add is a small step or something else that allows me to stand a bit taller. I am 2m tall but still the pushing out of the last segments is heavy work.

Projects - 4m slim jim antenna

As I wrote before I now have a working 4m set-up using the 4m transverter kit from DF2FQ (XV4-40). I also have a compact 2/4/6 meter beam that I will describe in more detail in a future post.

Although the beam is compact, I cannot use it at home as it is too large. How can that be? Well, I don't have a fixed mast - all my antennas start from my attic. I use a 20 meters long sloping end fed wire from my attic into the garden in an L shape for 80m-10m (resonant on 40/20/10m - works OK for 40-30-20). For 6m I use a vertical end fed wire that I put on a fiberglass pole in the attic and then push up through an attic window (I sometimes use this construction for lower bands as well). For 2m I have a compact 4 element beam that I can just push through the same attic window. I attach that one to an aluminium push up mast.

The 2/4/6m beam is just too large to fit through the attic window. So for working Es - one of my favourite sub hobbies - I needed a solution for 4m (having 6m and 2m covered). With Es you can get good results even with a "simple" vertical - as I have already experienced using my end fed wire for 6m. So, it was time to create a 4m vertical. Using a bit of ladder line PG8M had lying around and a nice online calculator by M0UKD (with construction tips), I created a slim jim for 4m.

Ladder line as the basis for the Slim Jim antenna

The online calculator and all the other info on John's page give you a good starting point but then you are tasked with finding the exact feed point position. As John M0UKD notes, it is important to perform the final tuning in a set-up that resembles your target situation. I stuck the ladder line to my fiberglass pole in the garden and pushed that up a couple of meters to make sure the antenna was away from obstacles (as I will be using it when I push it out from my attic). I tried different feed point positions, each time making measurements with my VNA.

Locating the feed point

Finding the feed point position is a trial and error process. This is slightly complicated by the wires being insulated. I didn't like the idea of having to remove the insulation on a large stretch to find the right spot, so I used the set-up in the picture above: two needles connected to my VNA. That way I could try different points and check the effect on the antenna SWR curve.

Finally I added a W2DU style current choke on approx 1m of coax (soldered to the feed point) that conveniently terminates with a SO-239 connector: ready to go.

The end result gives me an antenna with an SWR of 1:1.6 on 70.200. I might improve that a bit more by tweaking the stub length in the future but as it is I am pleased to know I am ready for next year's Es season.

First 4m QSO - getting a transverter kit working

Almost a year ago I bought a 4m transverter kit from DF2FQ (XV4-40). I have basic understanding of electronics, acquired in part through the hobby but building a project like this was new to me. With my mechanical engineering background I am more confident in building robust stuff like antennas, masts, supports, baluns, etc. Soldering loads of tiny components on a board seemed challenging. 

However the level of documentation provided by DF2FQ and some motivating words by PG8M - who was already using the transverter - pushed me to the point that I ordered the kit. When I received the package I must admit it looked daunting. 

Lots of parts..

..and rather tiny

I started building the kit sometime in August last year. I tried to work as meticulous as I could (a challenge when you are as impatient as I am). When I had completed the kit and ran the first tests, I found that I received 70 Mhz signals with the radio tuned to 29Mhz. Hurray!

However, when I tried to transmit, the transverter appeared to be dead as a dodo. No LED, no signal. A very disappointing result. I did some tests (as far my knowledge goes) and could not find the cause of the failure. So the kit went back in the box it was shipped in. Time for other projects.

The Es season is rather good this year and I have enjoyed the effects on 6m but 4m was open a lot of times as well. I really had to get back to the abandoned transverter project. PG8M had already kindly offered to help me months ago and today I took him up on his offer. We went through the error checking process step by step, finding and fixing four major issues. It turned out I had made two soldering errors and two of the smd resistors were faulty. Whatever happened to these resistors I really don't know.

PG8M trying to locate the next error

The good news is that we ended up with a transverter that delivered up to 35W on 4m with 5W drive on 10m. 

There was no one around to do an on air test so back home I hooked up the transverter and put my tri-band yagi on a pole @2m high in the garden. PG8M was QRV 30km away with his 4 ele beam pointing in my direction. That is when I made my first 4m QSO.

DK7ZB tri-band beam in action twice this week

It is a bit late in the Es season but I am sure I will get back to this band in the future. The next thing I need is an antenna I can set up quickly at home in case of any high MUF situations. For 6m I use an end fed wire that I can attach to a pole that I push through the attic window. For 4m I am going to try a slim jim vertical. More on that later.

Projects - Inverted V antennas for the low(er) bands

Choosing a /P antenna for 80m

My favourite antenna when working /P is the end fed half wave, set up vertically. It is easy to set up and works well with reasonable DX performance. It will not beat my portable hexbeam when working DX but that one requires more time, material and open space to set up.

The EFHW vertical becomes a challenge however on the lower bands. Now I did get myself the largest Spiderbeam pole - so a vertical half wave for 40m is an option - but there is a limit and 80m will definitely not fit.

One option then is to use a quarterwave vertical. However this requires radials if you want the majority of your signal to be radiated above ground. I developed a quarter wave for 80m with four elevated radials and it works but is quite a hassle to set up. Working /P you don't always have room for four elevated radials.

Another option is to use the EFHW sloping. That is a good option and I have used it on numerous occasions. If the support is tall enough to allow for an angle around 45 degrees the antenna still has a low angle of radiation but also a lobe at a high angle. That makes it a versatile antenna. It has some directivity - in the direction of the slope. 
The challenge on 80m is that the EFHW sloping still requires a tall support for a reasonable (steep) sloping angle otherwise you will end up with only the high angle radiation. 

Inverted V antenna

Another option - using a single support - is to use an inverted V dipole antenna. For 80m I find it a convenient antenna to set up and it comes with a unidirectional radiation pattern (in the horizontal plane) that fits my needs when I am "being chased" with chasers from all directions.
The inverted V has a high angle of radiation. On my 18m pole it very much resembles a sloping half wave dipole of the same length. The main difference is that the sloping wire will have 6dB F/B ratio while the inverted V is omnidirectional. It is very much up to what you are looking for.

Practically when working on 60m or 80m (or 160m) - for more than a few QSOs - I choose the inverted V antenna. When my tallest support still was only 12m I also chose the inverted V as my default antenna for 40m.  

For my inverted V antennas I developed a universal center connector that fits on the fiberglass poles I use. It is a simple component made from 40mm PVC that allows me to connect various wires to a SO-239 connector. The reason I designed it with changeable wires is that it allows me to make different combinations like 40m and 80m inverted V's on one pole fed by one coax cable. 



The tie wraps on the sides are used to keep the cable tension away from the soldered cable shoes - otherwise the shoe will certainly break in due course. The hole through the center allows it to slip over the top segment of my fiberglass poles.

I developed a couple of these center connectors so I can set up different antennas at the same time. We use them for example with the YNOMY DX Group during the PACC contest when we set up three different inverted V's (40/80/160). We then have the 80m and 160m on the tallest mast together, being fed from one coax cable.

For each inverted V I have two separate dipole legs. Each dipole leg is cut to the right size and features a cable shoe as visible in the first picture. To hold the wire I have constructed a cable spool consisting of a piece of PVC (40mm) with two end caps. On each end caps I have glued a piece of wood and through the end caps and wood I have put a piece of threaded wire. 

40m wire spool (one leg)

This spool holds the antenna wire plus a long enough end of tension string. I find it works rather conveniently in that I can just stick the spool in the ground (slightly under an angle) where it unreels while I extend the mast. Once I am happy with the position of the mast and antenna I push the spool further into the ground, stopping it from turning. This way I do not need pegs or anything else to set up this antenna. 

Below you see an impression of the antenna with four legs - dipoles for 80m and 160m - ready to be deployed.

I just stick the spools in the ground in the direction I want the leg to go. Then I extend the fiberglass pole with the spools unreeling until the mast is fully extended. Then I pick up each spool and place it where I want the end point to be. The advantage of the spool unreeling is that there is only a slim chance the legs get entangled even when you have two dipoles on one mast - the wires are kept under some tension the whole time. 

Projects - 18m pole set-up improvements

I use a variety of antennas and poles/masts when /P. The 12m HD Spiderbeam is the most compact one I have and is easy to set up in the field without any supporting structures. The bigger ones I normally attach to the car one way or another or to any suitable construction I can find around the place I am going to be active from. My favourite and most versatile antenna pole is the Spiderbeam 18 HD fiberglass pole. I use it almost every /P activity. Preparing for a tour through LX I decided to implement some improvements that make the pole even more portable.

Guying the 18m Spiderbeam pole
I have twice set up the 18m HD Spiderbeam pole on my own using an ingenious structure with all the 6 guy lines extending while I pushed out the segments. That took quite a bit of time so I looked for another option. When I set up the pole using the car or a supporting structure I find that I do not use any of the supplied guy lines - so it should be possible to find a much simpler configuration to set up this pole in the field.

I decided to try and set it up with only the lower segment guyed. That would allow me to simply set up the pole while it is still collapsed and then push out the segments without worrying about any other guying arrangement.

Borrowing from the idea behind the clamps Spiderbeam supplies for keeping the segments extended, I bought a hose clamp and applied rubber lint that I crimped in place. I cut some of the rubber away so I could add three rings. So now I have a permanent feature on my Spiderbeam pole: fixed guy rings. 

Securing the base
You also need the bottom part to stay put. Before I would use a large peg with some soft (insulation) material around it. I would just position the pole over this peg. However I have found this is not a very solid construction - e.g. it does not allow you to keep the pole standing while it is still collapsed. With the set up I just came up with, I need the collapsed pole to stay upright while I attach the lower guy lines. So I replaced the peg with this:

The center hole fits around the pole while the other holes can hold pegs that secure this little box in its place. Trying it in the field it turned out to work well - the Spiderbeam pole kept upright while I attached the lower guys.

With these two changes I can set up the pole in no time without needing any supporting structure, like so:

I used this a couple of hours with the pole extended 18m holding an efhw wire. Granted, it was not very windy that day. I will have to see if this is strong enough in higher winds.

Practical segment clamps
One last adjustment I made to the configuration is a replacement of the clamps that hold the segments in place when extended. The default clamps provided by Spiderbeam require a spanner or wrench to open and close. That is inconvenient and so I really did not use them often. I either extended the segments to the point that they stuck (with the risk that the antenna would collapse during a QSO) or I would use duct tape (that is quick to apply but not so easy to take off). 

So I bought clamps that have butterfly tightening tabs. I added rubber strip on the inside that I crimped on the clamps to protect the pole (like with the original clamps). I tried them and they work well.

Project - Mast support for heavy masts

For my portable endeavors I have built an aluminum push up mast and I have bought various fiberglass poles from Spiderbeam. I actually started out with a 10m pole from Spieth. That was rather thin, so I went for the 12m HD version from Spiderbeam.
To get my inverted v's for the low bands up higher I then bought the 18m version and recently I went even further and got myself the tallest pole they sell - 26m.  

Heavy masts present a challenge when working /P. I can manage to set up the 18m pole in the open field on my own but it is quite a bit of work and it would be a really daunting task with the aluminum mast and the 26m pole. [Note that I managed to do just that - setting up a 26m pole on my own in the field: https://www.ph0no.net/2017/10/one-man-set-up-for-26m-spiderbeam-pole.html]

When I built the aluminum mast I went looking for a proper mast support that I could use with my car. Typically this would mean a drive-on support. The ones I found on the internet however were too light for my sturdy (and heavy) mast.

Not having any welding tools available to me at the time (I now have an arc welding machine), I decided to build something myself out of wood. After some experimentation I went for a design where I attach the support to the wheel using lashing strap, instead of driving on the support.

If you are reading this to try something yourself, keep in mind this design only works if you have spoke rims on your car.

I never got around to write something about this support, even though I got questions about the design. After buying the 26m pole I had to build a new support - for a much larger diameter mast - so I decided to take some pictures in the process.

The end result looks something like this (showing my first version):

The tried and trusted version from different angles - note the rubber pads that go between the support and the car tire:

I constructed the old one for my aluminum mast that has a diameter of 70mm. It can also hold the 18m Spiderbeam fiberglass pole. Conveniently the tall vertical wooden beams are the same width as the bottom segment of the mast. This means that the only spacing that is critical when you build it, is the spacing between the two vertical wooden beams.

Now for the 26m I built the same support but I could not find wooden beams of the desired width, so I used the nearest (smaller) width and added planks to end up with the correct width - as you can see in the picture below.

Wooden parts cut to desired lengths 

Now that the vertical beams are of the correct width, the only spacing you have to worry about is the one between the two vertical wooden beams. I used the bottom segment of the Spiderbeam pole to define the space, as shown below.

The length of the horizontal wooden beams is not critical. They define the space between the car tire and the mast / pole. I use an extra 130 mm to leave enough room for my shoes - so that I can use the support to position myself higher when I push out the mast segments.

The height of the upper horizontal beam is critical in the sense that you need to make sure it stays within the height of the car tire (more about that later).

Once all the horizontal beams have been added the support looks something like this:

What is left, is adding the frame that you can tie to your car rim. I use 44x44mm wooden beam for this frame. The height and width for this last rectangular frame have already been defined by the structure you have created so far. It is therefore important that the upper horizontal beam I referred to earlier, is positioned at a height that puts the top of the frame we are now going to add right against the rubber of your car tire.

When I completed this stage I took two more steps: a piece of (ply)wood on the bottom of the support - this keeps the mast / pole from getting stuck in the ground (e.g. in case of a muddy underground). And I add pieces of rubber that go between the car tire and the wooden frame (refer to the pictures above of the old version).

Now you have the lower support for your mast. This might be enough to keep your mast straight up. In my case I added a second support on the roof of the car. This helps keep the heavier masts (like my aluminum mast and the 26m Spiderbeam pole) straight up without guying. 

This roof support is nothing magical. It is simply a wooden beam (44x44mm) that is longer than the width of your car + the distance to the mast. At one end I add two pieces of wood at a distance that equals the width of the mast. Through these pieces of wood I put a threaded rod (M8). This rod is positioned at such a distance that it keeps the mast in place. I use some pvc pipe to keep the keep the sharpish threads from damaging my mast / pole. This roof support looks like this:

I use lashing strap to attach the support to a roof rack on my car.