[Elecraft] EFHW

[Wes Stewart]

It is with some reluctance that I smack this whole EFHW tarbaby, but here goes.  
Comments in no particular order:

1)  A resonant antenna (even one that is self-resonant), e.g. one with a 
non-reactive feedpoint, isn't necessarily "efficient."  A quarter-wavelength 
monopole over lossy earth leaps to mind.

2)  A non-resonant antenna isn't necessarily inefficient.  The ever popular G5RV 
isn't resonant on the band of interest (20M) but when fed appropriately, was as 
efficient as a resonant dipole.

3)  Consider a BC band 1/2 wavelength vertical antenna.  Does the station 
designer say, "Well, this EFHW doesn't really doesn't need much of a 
counterpoise, so I'll just throw a 100' long wire on the ground and call it good 
enough?"  No, he install 120 radials that are even longer than the ones he would 
use under a 1/4 wavelength monopole.  Devoldere in "Low-Band DXing, Chapter 9, 
Section 4.3 says: "Here comes another surprise. A terrible misconception about 
voltage-fed verticals is that they do not require either a good ground or an 
extensive radial system.'"  Later in the same section he says, "Therefore it is 
even more important to have a good radial system with a voltage-fed antenna such 
as the voltage-fed T or a λ/2 vertical. These verticals require longer radials 
to do their job efficiently compared to current-fed verticals."

3)  When you backpacking mountain goats say, "Hey my wire isn't a vertical, it's 
mostly horizontal", I say, if your radio is sitting on a boulder or the ground, 
it's a vertical and your wire-on-the-ground counterpoise proves it.

Wes  N7WS



On 2/11/2017 2:33 PM, Ron D'Eau Claire wrote:
> All efficient antenna systems are "resonant" (jX=0) but the shorthand often
> used is "resonant" to mean "self resonant". That is true of any 1/4
> wavelength long radiator (again our common shorthand is usually "1/4 wave
> wire") or any multiple thereof worked against ground. It is also true of any
> half wave length radiator or any multiple thereof. (Note that these are
> electrical lengths, taking into account any surroundings including the
> radiator itself.)
>
> While self-resonant antennas do not present a reactive load to the source of
> RF power, the value of R, the resistance, may vary widely. There is nothing
> magic about the 50 ohm load most of our transmitters are designed for.
>
> However, a half wave radiator fed at the center presents a resistive value
> near 50 ohms when fed at typical heights above ground (in free space it is
> 75 ohms). Half wave antennas became very popular after WWII because 50-ohm
> coaxial feed line became abundant and cheap on the "surplus" market and Hams
> were taking steps to deal with needing to avoid interfering with the rapidly
> growing number of TV sets in nearby homes, including the Ham's own living
> room.
>
> In the following decades, greater and greater demands on harmonic
> suppression have led to Ham transmitters with output filters specifically
> designed for a 50 ohm load instead of being able to match a wide range of
> load impedances.
>
> So we have now moved the wide-range output network that was in Grandpa's Ham
> transmitter out of the transmitter and into what we call an "Antenna Tuner".
> But, of course it does not "tune" an antenna at all. It's just a matching
> network to be sure the transmitter is delivering power to a load close to 50
> ohms and non-reactive.
>
> 73, Ron AC7AC
>
> -----Original Message-----
> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Wes
> N7WS
> Sent: Saturday, February 11, 2017 12:44 PM
> To: Charlie T, K3ICH
> Cc:elecraft at mailman.qth.net
> Subject: Re: [Elecraft] EFHW
>
> jX = 0
>
> Sent from my iPhone
>
>> On Feb 11, 2017, at 1:29 PM, Charlie T, K3ICH<pincon at erols.com>  wrote:
>>
>> Define "resonance".
>>
>> Chas
>>
>> -----Original Message-----
>> From: Elecraft [mailto:-bounces at mailman.qth.net] On Behalf Of Fred
>> Jensen
>> Sent: Saturday, February 11, 2017 2:40 PM
>> To:elecraft at mailman.qth.net
>> Subject: Re: [Elecraft] EFHW
>>
>> Ummm ... A full-wavelength wire is not resonant?
>>
>> 73,
>>
>> Fred ["Skip"] K6DGW
>> Sparks NV DM09dn
>> Washoe County
>>> -----Original Message-----
>>> From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of
>>> Lynn W. Taylor, WB6UUT
>>> Sent: Friday, February 10, 2017 12:13 PM
>>> To:elecraft at mailman.qth.net
>>> Subject: Re: [Elecraft] EFHW
>>>
>>> Just a reminder, folks.
>>>
>>> If it's not a half-wave, then it's a non-resonant wire.
>>>
>>>