Difference between revisions of "7-band OCF dipole"

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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.  Includes 4:1 voltage balun.
 +
 +
2m SWR measurements below just for fun :)
 +
 
== Suspension ==
 
== Suspension ==
 +
[[File:80m OCF suspension (current).png|850px|current wiring configuration]]
  
 
== Wiring ==
 
== Wiring ==
−
[[File:80m OCF configuration.png|800px|wiring configuration]]
+
[[File:80m OCF configuration.png|850px|wiring configuration]]
 +
 
 +
[[File:80m OCF wiring picture.jpg|thumb|a photo of the wiring setup]]
  
 
== Measurements ==
 
== Measurements ==
−
=== Initial SWR 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:
 +
 
 +
[[File:80m OCF suspension (original).png|850px|original wiring configuration]]
 +
 
 
==== From shack ====
 
==== From shack ====
 
[[File:2020-09-21 shack 80m.jpg|200px|80m]]
 
[[File:2020-09-21 shack 80m.jpg|200px|80m]]
Line 13: Line 26:
 
[[File:2020-09-21 shack 12m.jpg|200px|12m]]
 
[[File:2020-09-21 shack 12m.jpg|200px|12m]]
 
[[File:2020-09-21 shack 10m.jpg|200px|10m]]
 
[[File:2020-09-21 shack 10m.jpg|200px|10m]]
−
 
+
[[File:2020-09-21 shack 6m.jpg|200px|6m]]
  
 
==== Under antenna, with coax segment 1 ====
 
==== Under antenna, with coax segment 1 ====
Line 20: Line 33:
 
[[File:2020-09-21 antenna 20m.jpg|200px|20m]]
 
[[File:2020-09-21 antenna 20m.jpg|200px|20m]]
 
[[File:2020-09-21 antenna 10m.jpg|200px|10m]]
 
[[File:2020-09-21 antenna 10m.jpg|200px|10m]]
 +
 +
=== After raising long end to ~8ft, 2020-09-23 ===
 +
 +
==== Under antenna, with coax segment 1 ====
 +
 +
* red = straight
 +
* blue = with hand on coax ring
 +
 +
[[File:2020-09-23 antenna 80m.jpg|200px|80m]]
 +
[[File:2020-09-23 antenna 40m.jpg|200px|40m]]
 +
 +
==== From shack ====
 +
 +
[[File:2020-09-25 shack 80m.jpg|200px|80m]]
 +
[[File:2020-09-25 shack 40m.jpg|200px|40m]]
 +
[[File:2020-09-25 shack 20m.jpg|200px|20m]]
 +
[[File:2020-09-25 shack 10m.jpg|200px|10m]]
 +
[[File:2020-09-25 shack 6m.jpg|200px|6m]]
 +
[[File:2020-09-25 shack 2m.jpg|200px|2m]]
 +
 +
(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
 +
 +
[[File:2020-10-06 antenna 80m.jpg|200px|80m]]
 +
[[File:2020-10-06 antenna 40m.jpg|200px|40m]]
 +
[[File:2020-10-06 antenna 20m.jpg|200px|20m]]
 +
[[File:2020-10-06 antenna 17m.jpg|200px|17m]]
 +
[[File:2020-10-06 antenna 12m.jpg|200px|12m]]
 +
[[File:2020-10-06 antenna 10m.jpg|200px|10m]]
 +
 +
==== From shack ====
 +
 +
[[File:2020-10-06 shack 80m.jpg|200px|80m]]
 +
[[File:2020-10-06 shack 40m.jpg|200px|40m]]
 +
[[File:2020-10-06 shack 20m.jpg|200px|20m]]
 +
[[File:2020-10-06 shack 17m.jpg|200px|17m]]
 +
[[File:2020-10-06 shack 12m.jpg|200px|12m]]
 +
[[File:2020-10-06 shack 10m.jpg|200px|10m]]
 +
[[File:2020-10-06 shack 6m.jpg|200px|6m]]
 +
 +
=== After adding choke, 2020-10-25 ===
 +
 +
[[File:2020-10-25 choke.jpg|thumb|200px|the choke]]
 +
[[File:2020-10-25 choke connected to antenna.jpg|thumb|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 and length, an old Radio Shack patch.
 +
 +
In assembly and installation, I noted three things:
 +
# The coax segment I used for the choke is rather old, and is of unknown quality.
 +
# 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?
 +
# 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?
 +
 +
<div style="clear: both;"></div>
 +
 +
 +
==== Under antenna, with coax segment 1 ====
 +
* red = straight
 +
* blue = with hand on coax ring
 +
 +
[[File:2020-10-25 antenna 80m.jpg|200px|80m]]
 +
[[File:2020-10-25 antenna 40m.jpg|200px|40m]]
 +
[[File:2020-10-25 antenna 20m.jpg|200px|20m]]
 +
[[File:2020-10-25 antenna 17m.jpg|200px|17m]]
 +
[[File:2020-10-25 antenna 12m.jpg|200px|12m]]
 +
[[File:2020-10-25 antenna 10m.jpg|200px|10m]]
 +
[[File:2020-10-25 antenna 6m.jpg|200px|6m]]
 +
 +
==== From shack ====
 +
 +
[[File:2020-10-25 shack 80m.jpg|200px|80m]]
 +
[[File:2020-10-25 shack 40m.jpg|200px|40m]]
 +
[[File:2020-10-25 shack 20m.jpg|200px|20m]]
 +
[[File:2020-10-25 shack 17m.jpg|200px|17m]]
 +
[[File:2020-10-25 shack 12m.jpg|200px|12m]]
 +
[[File:2020-10-25 shack 10m.jpg|200px|10m]]
 +
[[File:2020-10-25 shack 6m.jpg|200px|6m]]
 +
[[File:2020-10-25 shack 2m.jpg|200px|2m]]
 +
 +
=== After raising short end, 2020-11-08 ===
 +
 +
[[File:2020-11-08 antenna suspension.jpg|thumb|the antenna at its feedpoint]]
 +
[[File:2020-11-08 antenna support.jpg|thumb|a view showing the antenna and the tree that supports it from the short end and the hill situation, 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.
 +
 +
==== From shack ====
 +
 +
[[File:2020-11-09 shack 80m.jpg|200px|80m]]
 +
[[File:2020-11-09 shack 40m.jpg|200px|40m]]
 +
[[File:2020-11-09 shack 20m.jpg|200px|20m]]
 +
[[File:2020-11-09 shack 17m.jpg|200px|17m]]
 +
[[File:2020-11-09 shack 12m.jpg|200px|12m]]
 +
[[File:2020-11-09 shack 10m.jpg|200px|10m]]
 +
[[File:2020-11-09 shack 6m.jpg|200px|6m]]
 +
[[File:2020-11-09 shack 2m.jpg|200px|2m]]
 +
 +
=== After some weather, 2020-11-21 ===
 +
 +
After some wind and rain over the last few weeks, the feed point has started to droop a bit, but not terribly.
 +
 +
This time I'm testing from both sides of lightning arrestor to see effect the ground has.
 +
 +
==== Before lightning arrestor ====
 +
 +
* red = straight
 +
* blue = with hand on coax ring
 +
 +
[[File:2020-11-21 antenna 80m.jpg|200px|80m]]
 +
[[File:2020-11-21 antenna 40m.jpg|200px|40m]]
 +
[[File:2020-11-21 antenna 20m.jpg|200px|20m]]
 +
[[File:2020-11-21 antenna 17m.jpg|200px|17m]]
 +
[[File:2020-11-21 antenna 12m.jpg|200px|12m]]
 +
[[File:2020-11-21 antenna 10m.jpg|200px|10m]]
 +
[[File:2020-11-21 antenna 6m.jpg|200px|6m]]
 +
[[File:2020-11-21 antenna 2m.jpg|200px|2m]]
 +
 +
==== After lightning arrestor ====
 +
 +
[[File:2020-11-21 arrestor 80m.jpg|200px|80m]]
 +
[[File:2020-11-21 arrestor 40m.jpg|200px|40m]]
 +
[[File:2020-11-21 arrestor 20m.jpg|200px|20m]]
 +
[[File:2020-11-21 arrestor 17m.jpg|200px|17m]]
 +
[[File:2020-11-21 arrestor 12m.jpg|200px|12m]]
 +
[[File:2020-11-21 arrestor 10m.jpg|200px|10m]]
 +
[[File:2020-11-21 arrestor 6m.jpg|200px|6m]]
 +
[[File:2020-11-21 arrestor 2m.jpg|200px|2m]]
 +
 +
==== From shack ====
 +
 +
[[File:2020-11-21 shack 80m.jpg|200px|80m]]
 +
[[File:2020-11-21 shack 40m.jpg|200px|40m]]
 +
[[File:2020-11-21 shack 20m.jpg|200px|20m]]
 +
[[File:2020-11-21 shack 17m.jpg|200px|17m]]
 +
[[File:2020-11-21 shack 12m.jpg|200px|12m]]
 +
[[File:2020-11-21 shack 10m.jpg|200px|10m]]
 +
[[File:2020-11-21 shack 6m.jpg|200px|6m]]
 +
[[File:2020-11-21 shack 2m.jpg|200px|2m]]
 +
 +
[[Category:Amateur radio]]

Latest revision as of 14:15, 22 November 2020

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. Includes 4:1 voltage balun.

2m SWR measurements below just for fun :)

Suspension

current wiring configuration

Wiring

wiring configuration

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:

original wiring configuration

From shack

80m 40m 20m 17m 12m 10m 6m

Under antenna, with coax segment 1

80m 40m 20m 10m

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

Under antenna, with coax segment 1

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

80m 40m

From shack

80m 40m 20m 10m 6m 2m

(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

80m 40m 20m 17m 12m 10m

From shack

80m 40m 20m 17m 12m 10m 6m

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 and length, an old Radio Shack patch.

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

80m 40m 20m 17m 12m 10m 6m

From shack

80m 40m 20m 17m 12m 10m 6m 2m

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 and the hill situation, 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.

From shack

80m 40m 20m 17m 12m 10m 6m 2m

After some weather, 2020-11-21

After some wind and rain over the last few weeks, the feed point has started to droop a bit, but not terribly.

This time I'm testing from both sides of lightning arrestor to see effect the ground has.

Before lightning arrestor

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

80m 40m 20m 17m 12m 10m 6m 2m

After lightning arrestor

80m 40m 20m 17m 12m 10m 6m 2m

From shack

80m 40m 20m 17m 12m 10m 6m 2m

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