[Elecraft] Single Band 40 Meter Dipole

[Jim Brown]

On 12/31/2011 9:14 PM, Phil Hystad wrote:
> Or, maybe a 1:1 balun right at the antenna feed point with coax the remaining distance to the shack?

No question -- 50 ohm coax wound around one or more #31 or #43 ferrite 
cores to form a common mode choke.  See 
http://audiosystemsgroup.com/RFI-Ham.pdf   The choke will completely 
kill any radiation or pickup from the feedline.  If the antenna were a 
lot higher, I'd use 75 ohm coax.  And yes, tweak the length for 7.1 MHz.

Also see two applications notes about "antennas for limited space" on my 
website. A single 2-wire fan dipole cut for 80M and 40M and fed with 50 
ohm coax will also work great on 30M, 17M, 15M, and 12M, and using the 
same choke to kill feedline current. To minimize feedline loss on 30, 
17, 15, and 12, use RG8 rather than RG8X or RG58. This antenna will work 
as well as the single-band 40M dipole on 40M.  You WILL need an antenna 
tuner, like the KAT3.

http://audiosystemsgroup.com/publish.htm

73, Jim K9YC