[TowerTalk] Low 160m Dipole - how bad?

[Jim Brown]

On 1/13/2025 12:11 PM, john at kk9a.com wrote:
> I have tried a low 160m dipole/  inverted V many times from the Caribbean
> and they are incredibly bad.  I had much better luck on 80m with a low
> dipole.  On top band you usually need something vertically polarized for TX.

Yes. It has to do with how vertically and horizontally polarized 
wavefronts interact with the earth and the ionosphere. I explored this 
extensively in this long modeling study, the results of which are well 
understood, experienced by many over the years.

http://k9yc.com/AntennaPlanning.pdf

For several years after moving to W6 in 2006, I had both a half-wave 
160M dipole at 120 ft and a 100 ft Tee vertical with a lot of long 
radials, and spent a lot of time, especially at the beginning, switching 
between them. The dipole, even at that height, rarely won.

This was especially true during daylight hours (the first 3 hours of 
most Topband contests for those of us on the west coast). Running legal 
limit from my QTH south of San Francisco, I could regularly work big 
stations out to 800 miles or so on the first call -- Phoenix, Seattle, 
Salt Lake, NM, and western CO as early as the 2 pm PST start, BUT ONLY 
ON THE VERTICAL. Calling on that 120-ft high dipole wouldn't even get a QRZ?

On the other hand, Tree is absolutely right about variations in vertical 
arrival angle through the day. BUT -- as that modeling study shows, low 
dipoles are NOT more efficient (that is, do NOT radiate more signal) at 
high angles than high ones, but they do RECEIVE better. You need to look 
at the vertical plots where the plots of dipoles at increasing height 
are plotted on the same graph, and the graphs derived from those plots 
showing low-angle and high angle field strength vs height. For the 
non-technical among us, double the heights on the 80M plots for topband.

Many years ago, N6RO told me that that he patches lots of different 
antennas to the 160M operating desk for topband contests.

When I presented this material to NCCC, all the OTs and good engineers 
were in agreement with my study.

And my bottom line has always been to 1) learn as much as you can about 
how antennas and propagation work, 2) load up what you have call CQ, and 
pay attention to how that antenna works; and 3) if you have other 
options try them too.

73, Jim K9YC