Temporary ham HF antenna

[dtvmcdonald]

I'm looking for web sites that discuss making your own HF (40-10 meters) antenna system for apartment dwellers.

I already have one for myself which I designed and built. It is on all bands an off-center fed slightly sloped dipole. It uses different lengths for each band,
such that one adds a piece on the est end of the 10 meter dipole for 12m, then adds a piece on the east end for 15 meters, then adds to the 12m west side a second piece for 17 meters, etc. Changing bands takes about 5-7 minutes.

I have not seen any descriptions of such an adjustable system setup. I'm making a presentation describing my antenna and would like to see if others have described such a system before.

Mine works very well with SWR of better than 1:1.6 on all bands and results I would expect from the peak height (21 feet), i.e. it burns clouds on 40 meters.

Doug McDonald

[mr_rye89]

A magnetic loop perhaps? I have an end fed dipole for portable use and my Xiegu g90 seems to tune it up just fine, but it's probably not practical for an apartment. There's also those Ham Stick things with a coil on the bottom with multiple taps for each band, might be worth a look if you have a balcony to attach to

[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.