I had an old 12m spider pole, these are very robust versions of the antenna pole and suitable for many applications.
As this was a semi permanent solution, I tapped up the joints in the pole with self amalgamating tape. Its also possible to buy a clamp system, suitable for clamping each section of the mast. The mast will need to be guyed, so a suitable guy ring and UV stable cord will be needed for the guys.
I looked up the best length of wire to run vertically up the pole, and decided on 10.8 meters. This length should provide a reasonable match once coupled with a 9:1 transformer.
The type of balun you choose will depend on power levels and if you require it to be weather resistant. If you plan to do data modes or CW the you will need to factor in the power handling for these modes. 100w data modes, will require a higher power handling.
So once the pole is installed, and guyed you will need to consider how to tune and manage common mode currently. While the 9:1 will bring the antenna closer and make it manageable to tune, it will not be a 50 Ohm match so you have two options available
ATU in the shack
Its possible a ATU built into the radio or shack based will handle the mismatch, but the disadvantage is the feeder loss could be considerable. Providing a match at the radio, when using coax is less than idea.
Remote ATU
Matching the antenna to 50 Ohm, and then feeding it with coax solves the issue identified above, but the remote ATU will need to be powered and waterproof.
Common mode choke
Its very likely you will need to suppress common mode currents on the outside of the coax, without this the coax could radiate and RF could be present in the shack. If you are using data modes, this will cause issues with the PC, soundcard and mouse control. RF in the shack is never good, you really want it outdoors. Using a 1:1 choke in the coax feed and or close to the 9:1 coax should prevent this from becoming an issue.
You can simply wind 8 or more turns of coax onto a FT240-43 toroid, the yellow wires are radials.
Radials
Elevated are best, and you should aim for 4 or more. The advice seems to be not resonant lengths, but 4 or more of various lengths from 3 to 5m should work well depending on space available.
The good and the bad
The antenna using a remote ATU will tune on 3.5, 5, 7, 10, 14, 18, 21, 24 and 28. In theory that is 9 bands. In practice the lower and upper bands have issues due to the wire length.
3.5 MHz the wire is just too short at 10.8m, while it may provide some local contacts, it is very inefficiant
28 MHz the wire is too long, at just over 1 wavelength its a cloud warmer and at best has a very spiky radiation pattern.
The other bands are OK, with 7, 10, 14 and 21 being good. Performance is subjective, but having made around 400 QSO this month I have a reasonable idea. You can work some DX, but the higher bands are challenging. If you are looking for a multi band vertical, that will work and is a compromise then this is both cheap and multiabnd.
You could buy a commercial muti-band vertical, they could cost you £200, £300 or more or you could try something much cheaper. If you get bored with the vertical, then you could re-purpose the pole for portable use.
Experiment, have fun and be sure to let me know what works fort you.
