7-band OCF dipole

80m 7-band off-center-fed dipole bought from gniklat1 on eBay.

Advertised to work on 80m, 40m, 20m, 17m, 12m, 10m, and 6m (tuner needed to cover all of 80m and 10m), with max power 300W PEP, 150W CW, 75W Digital. Advertised to work best in an inverted V configuration with the center at 25-30ft and ends at 8-10ft above ground.

2m SWR measurements below just for fun :)

Suspension

Wiring

a photo of the wiring setup

Measurements

Initial SWR measurements, 2020-09-21

Long end of antenna only ~6ft off the ground, support rope on long end only ~20ft off the ground. Looked something like this:

From shack

Under antenna, with coax segment 1

After raising long end to ~8ft, 2020-09-23

Under antenna, with coax segment 1

• red = straight
• blue = with hand on coax ring

From shack

(Better on 2m than most of the bands it's supposed to work on...)

After raising rope on long end another ~5ft, 2020-10-06

The center is maybe a foot (or two??) higher than previously.

Under antenna, with coax segment 1

• red = straight
• blue = with hand on coax ring

From shack

After adding choke, 2020-10-25

the choke

the choke connected to the antenna

I made a guanella-like choke, with 17 turns of RG-58/U coax around an FT240-43 ferrite. I found a perfect length of coax with just the right terminals, an old Radio Shack length.

In assembly and installation, I noted three things:

1. The coax segment I used for the choke is rather old, and is of unknown quality.
2. The PL-259 on the choke coax really didn't want to go onto the antenna, and I had to use a pair of pliers to tighten it, and ended up stripping most of the "grip" off the ring. I'm still not sure I got it on fully tightly—I think the teeth maybe mostly are locked in place but maybe not pushed up against the SO-239 so well?
3. The PL-259 on the coax that was attached to the bottom of the antenna (and which I then attached to the choke) had water inside it after I took off the "rescue tape" around it and unscrewed it. I wonder if there might be water inside the balun?

Under antenna, with coax segment 1

• red = straight
• blue = with hand on coax ring

From shack

After raising short end, 2020-11-08

the antenna at its feedpoint

a view showing the antenna and the tree that supports it from the short end (as well as the feed point into the house).

I raised the short end a foot or two and tightened things up. The overall effect on SWR in the shack was a lowering of the dips, especially on the lower bands.

The center could probably still stand to be raised. The antenna is currently suspended from the lowest branch of the tulip tree in the picture to the right; I'm considering trying to suspend it from the next branch up.