[TowerTalk] UL listed protector for ladder line

[Jim Brown]

On 6/16/2025 6:13 PM, john at kk9a.com wrote:
> A fan dipole or the loaded dipole that K9YC suggested would have a consistent pattern with no deep nulls and ~50 ohm impedance on the designed bands.

Yes, and this is a really important factor. The lobes are quite broad, 
the depth of the nulls depends a lot on symmetry and surrounding 
conductors. They're only very deep with very good symmetry, and because 
the lobes are so broad, the only thing really matters more than about 6 
dB is where the nulls are.

An important point about SWR. Especially on the lower HF bands, excess 
attenuation due to SWR is a lot less than imagined. I load an 80M dipole 
fed with about 160 ft of RG11 that's at 120 ft to work 60M, where legal 
limit is 100W EIRP. SWR measured in the shack with an LP-100A is about 
5.5:1, which works out to about 7.5:1 at the antenna. Total line loss is 
on the order of 1.6 dB. The tuner in the KPA1500 happily puts about 150W 
into the feedline with about 2W from the K4. The antenna plays quite 
well, and I passed 100 countries on the band this winter. The only 
activity on the band is FT8. The limitation on what I can work is the 
limited number of countries active on the band and how well they can hear.

At this power level, the likelihood that high power arrestors would 
fault prematurely depends on whether line length establishes a high 
voltage at the arrestor.

73, Jim K9YC