[Elecraft] EFHW

Sat Feb 11 23:54:44 EST 2017

Ha, ha!!! Well put Wes! 

Some mountain portables erect low "horizontal" antennas on the side of a steep mountain. The result is a very low angle of radiation because, even though the main lobe is "straight up" from the mountainside from the antenna, the slope puts that lobe at a fairly low angle relative to the earth.

73, Ron AC7AC

-----Original Message-----
From: Elecraft [mailto:elecraft-bounces at mailman.qth.net] On Behalf Of Wes Stewart
Sent: Saturday, February 11, 2017 8:02 PM
Cc: elecraft at mailman.qth.net
Subject: Re: [Elecraft] EFHW

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.
>>>
>>>

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