Temporary ham HF antenna

[dtvmcdonald]

My apartment people attacked me for using tie points outisde my own apartment.
I had to design something that only touches the patio, so I did.

Its a near vertical, with a smaller horizontal part 8 feet off the ground.
Part of the antenna is a commercial (and expensive) stainless steel telescoping thing up to 17 feet long, the horizontal part is a wire also up to 17 feet. Between them is a vertical piece of Coax 5 feet long, which radiates. The coax has its outer insulation removed at the bottom and the horizontal part is attached there.
Just below this junction is the usual toroid choke balun.

I've never seen a description of something like this. It works fine, about the same as the old horizontal dipole one, but of course is mostly vertically polarized. The low angle radiation is all vertically polarized.

Simulation says that while the new one has a lower overall efficiency, the low angle radiation is much better on the lower frequency bands. This antenna covers 20-17-15-12-10-6 with SWR below 1.4:1 on all bands except 6 meters, which is 1.8:1. The transmitter agrees with the calculated values.

All bands except 6 can have the lowest SWR ajustable to any place by changing the extension of the collapsible part. 6 is fixed at the FT8 frequency.

I have designs for 30, 40, and 75 meters which are similar but don't have coax that radiates, and also need loading coils and a 1:4 (12.5 to 50 ohm) unun in addition to the current balun choke. The balun vendor is currently out of that balun ... hopefully soon. I tried making one and the design is right but the cores
I have are wrong.

I made it look fairly nice by using varnished house-trim grade poplar poles.
Its easier to install than the old one. The pole is self-supporting in a holder made of 100 pounds of decorator grade bricks glued together.