[Elecraft] EFHW

[Dan Presley]

I also wanted to thank Frank for a great suggestion.He hit it right on the nose. I always forget about the usefulness of an RF ammeter. When I was a kid in the ’60’s hanging around the OT’s a couple of them used these in the open wire lines to tune for maximum current. No concern of SWR as that wasn’t important with pi and linked outputs in your tube rigs! Now I just have to figure out a way to do this in the field…I still have some wonderful Weston meters one of the guys gave me lo those many years ago.
Dan Presley  N7CQR
n7cqr at arrl.net


> On Feb 12, 2017, at 10:45 AM, donovanf at starpower.net wrote:
> 
> 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 <mailto:donwilh at embarqmail.com>> 
> To: "Wes Stewart" <wes_n7ws at triconet.org <mailto:wes_n7ws at triconet.org>>, elecraft at mailman.qth.net <mailto: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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