[Elecraft] Multi Band Dipoles

[Jim Brown]

On Mon, 5 Jul 2004 10:37:25 +0100, Martin.Evans at simoncarves.com wrote:

>Mike, I've only been at this game for 12 months so can't really comment on
>the comparisons but my multi band dipole works a treat. It is a home brew
>set up with 3 horizontal dipoles cut for 80/40/20m one above the other with
>about 1-2 feet separation at the ends. All on the same coax with no balun
>or ground connection. 

I am very much a fan of parallel wire dipoles like yours, and have  built a half dozen of 
them so far for different combinations of bands (for Field Day, and for a station I'm 
putting together at W6BX). I use the DX Engineering balun, not so much for its power 
rating (2 KW continuous), but for its exceptional build quality and performance specs.  
An advantage of this construction is that each antenna is a full sized half wave dipole, 
and is thus tunes more broadly than one loaded by traps or loading coils. You also 
avoid the loss associated with traps. 

My construction uses 16" long spacers cut from PVC conduit (labeled UV resistant) 
and THHN wire that I bought at Home Depot. At W6BX, on a mountaintop where there 
is a lot of wind and ice, the long element that carries the load is #8 copper, while the 
parallel dipoles are #10. For Field Day, I used #12. 

That said, I am also quite pleased with the shortened 80/40 dipole that I bought from 
HyPower antenna company, and with the 160/80/40 antenna that I built using 
HyPower's loading coils. 

http://www.freewebs.com/hypower/

For the 80/40 design, the loading coils self resonate at 40 meters, so the inner dipole 
is a half wave on 40. The total length of the antenna (tuned for 3575) is about 90 ft, 
which lets it fit on my city lot. This antenna, about 45 ft high, has worked 34 countries on 
80 and 95 on 40 with 100 watts in about 9 months.  It also is pretty good in some 
directions on 30 meters. The 160/80/40 design is a scaled-up version of the 80/40 
design for 160/80, with a parallel wire dipole for 40. It is installed at W6BX, and works 
VERY well. 

Jim Brown K9YC