[Elecraft] Groundplane antennas (was: Re: Elecraft CW Net Announcement)

[Victor Rosenthal 4X6GP]

A symmetrical arrangement of radials (which implies more than one) will 
reduce common mode current and high-angle radiation, which are usually 
considered undesirable (although for local QSOs the high-angle radiation 
can be useful).

If you have an unsymmetrical radial arrangement, it's best to put a 
choke at the feedpoint to kill the common mode current. Almost in any 
case there will be some imbalance caused by nearby objects, so a choke 
is a good idea.

Two radials is slightly less efficient than three or four, but not that 
much.

73,
Victor, 4X6GP
Rehovot, Israel
Formerly K2VCO
CWops no. 5
http://www.qsl.net/k2vco/
.
On 27/07/2020 5:25, Fred Jensen wrote:
> It's a fairly simple antenna.  Yes, one radial is all you really "need," 
> a couple more help improve efficiency and increase the BW.  In the olden 
> daze [50's], we'd use 3 or 4 and cut them just a little different.  Also 
> increased the BW, especially on 10, and in the later 50's, 10 was open 
> 28000 - 29700, 24/7.  It's really a very forgiving antenna.  The 
> radials, with rope extensions are often used as guys as well.  The droop 
> angle will affect the main lobe elevation somewhat, but I'll bet I could 
> do a blind "taste" test with you and you'd never really know the 
> difference.  That angle is more often used to adjust the impedance at 
> the feed point.
> 
> Make that angle 90 deg and you have a vertical half-wave dipole 
> center-fed out of phase.  Make the elements 1/2 wave each, mechanically 
> easy on 10 and even 15, and cophase feed them in the center, and you 
> have a Franklin vertical [see KFBK, one of the last ones I know of]. 
> Very versatile basic design, works great, lasts a long time.
> 
> 73,
> 
> Fred ["Skip"] K6DGW
> Sparks NV DM09dn
> Washoe County
> 
> On 7/26/2020 3:38 PM, Rick NK7I wrote:
>> The reading I've done says only one radial is required; that the 
>> 'favoring' in the direction of the radial is not enough to be worried 
>> about; that there is no cancellation from opposing (or just more) 
>> radials.  I have used a single radial ground plane and found this to 
>> be true (at 6' over dirt on 80M).  It favors a morning net 800 miles 
>> away, yet worked DX in any other direction easily (then I moved to a 
>> rotating dipole at 60' which beats it out).  That ground plane easily 
>> beat out a horizontal dipole I used before them all (fixed, in the 
>> 'wrong' angle because of tree location).
>>
>> Both the radiator and radial are tuned (equally), but the angle of 
>> difference from dipole to the traditional 90 deg ground plane will 
>> cause the resistance to vary (roughly 72 ohms as a dipole, dropping to 
>> ~50 ohms when at 90 degrees),  So if another angle is chosen (inverted 
>> Y), to match a 50 ohm feedline (to have a 1:1 SWR), the element 
>> lengths are adjusted equally until that match is made; altering the 
>> resonance of the wires (maximum transfer of energy).  And inverted Y 
>> antenna would be between that 50-72 ohm range, still acceptably low 
>> SWR to not mess with.
>>
>> Which again, is not a significant variance, so put it up, try it out 
>> and compare to other antennas.  Wire is cheap enough to play with and 
>> try things out.
>>
>> Modeling will demonstrate the pattern and 'take off' angles quite 
>> clearly; reality is often different because of local objects, ground 
>> resistance, height...
>>
>> Don't forget to add a common mode current choke at the feed.
>>
>> 73,
>> Rick NK7I
>>
>>
>>
>> On 7/26/2020 11:57 AM, Don Wilhelm wrote:
>>> Fred,
>>>
>>> That would be correct if they are oriented at 180 degrees from each 
>>> other so as to cancel the horizontal radiation.  Elevated radials 
>>> must be tuned to be effective, but only 2 are needed. How much tuning 
>>> will depend on the height above ground.
>>>
>>> 73,
>>> Don W3FPR
>>>
> 
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