[Elecraft] EFHW

[donovanf at starpower.net]

Dan's original post concerned the effectiveness and practicality 
of various EFHW configurations in a man pack environment. 
Since he had already decided that his radiating element will 
be 1/2 wavelength long, the primary concern is power transfer 
efficiency vs. practicality of the solution in a weight and space 
constrained man pack environment. 


For the entire history of radio, RF ammeters have been used to 
evaluate the efficiency of alternative matching systems and their 
associated radial/counterpoise systems. An RF ammeter could 
be placed in Dan's EFHW antenna -- ideally in the center -- to 
compare the relative performance of practical man pack EFHW 
implementations. 


73 
Frank 
W3LPL 


----- Original Message -----

From: "Don Wilhelm" <donwilh at embarqmail.com> 
To: "Wes Stewart" <wes_n7ws at triconet.org>, elecraft at mailman.qth.net 
Sent: Sunday, February 12, 2017 6:29:07 PM 
Subject: Re: [Elecraft] EFHW 

Wes, 

I do not doubt what you are saying about 1/2 wave verticals, but most 
EFHW antennas are mounted as a sloper or a horizontal antenna. 

For portable operation, the main concern is for the ability to feed the 
antenna, and not about maximizing the far field strength. 

73, 
Don W3FPR 

On 2/12/2017 12:34 PM, Wes Stewart wrote: 
> Alas, if only this was true. 
> 
> Google "radial system design and efficiency in hf verticals" and you 
> should get a cached version of Rudy Severns' paper of the same name. In 
> it he states: 
> 
> "Alternately we can graph efficiency in terms of Ga as shown in figures 
> 3 and 4. Unfortunately this also shows how inefficient verticals are 
> even over very good ground. Very depressing! For example, with very good 
> soil (0.02/30) and 128 1/2-wave radials, the efficiency of a 1/4-wave 
> vertical is still only -2.76 dB (53%)!" 
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