I have taken the liberty to move Jim's most recent reply on the Common
mode thread over here where it is more on topic
Jim:
True enough
There is a work around however
Dick Weber k5UI ( SK ..I think) published an article in Communications
Quarterly in 1999 on an approach using non resonant ( i.e not .25
wavelength ) radials which significantly reduces the impact of
unbalanced radial currents. I cant find a link to a copy on the WEB, I
have a copy of the article (contact me off list) if you cant find one .
Running four 100 foot radials ( ~.2 wavelengths) I am able to have
(measured)� radial currents that vary less than 2% over all four radials
installed in a heavily wooded environment where some attempt was made to
try and keep all of them "around " 7' above ground
At .2 wavelengths N6LF's work suggests that I am giving up around .2db
...which suggests I might want to look at going from 100' radials to 150
/160' ? Will have to look at that, it would require I redo all my
matching networks not sure I want to go through that for .3db ...8^(
NR1DX
manuals@artekmanuals.com
On 1/1/2021 4:28 PM, Jim Brown wrote:
On 1/1/2021 12:09 PM, Mike Waters wrote:
I am ONE of the people who claim that four elevated radials can have
approximately the same efficiency as 120 buried quarter wavelength
radials.
N6LF's work on this showed that imbalance of the current in elevated
radials can significantly reduce field strength. Imbalance can be
caused by differences in heights, lengths, and soil underneath them.
Depending on our real estate, hams may find it difficult or
impractical to install elevated radials having the symmetry of a
broadcast station. Rudy has published work showing that 8 elevated
radials are better than 4 for this reason.
73, Jim K9YC
On 1/1/2021 4:55 PM, Mike Waters wrote:
Thanks for catching that, Dave!
I certanly can't argue with Rudy N6LF, but those two λ/4 10' high elevated
radials in my old 160m page made that inverted-L a "killer"* in an ARRL 160
contest about 10 years ago. That was using only 100 watts. Broke a number
of DX pileups, to my utter amazement.
*Having said that, I had nothing else to compare it to in an A/B test!
73, Mike
W0BTU
On Fri, Jan 1, 2021, 3:37 PM Artek Manuals <Manuals@artekmanuals.com> wrote:
Correction that should be N6LF (not N6FL)
NR1DX
On 1/1/2021 4:26 PM, Artek Manuals wrote:
N6FL was quoted earlier ...
https://www.antennasbyn6lf.com/design_of_radial_ground_systems/
However N6FL states "The article is primarily intended to show why I
(he, N6FL)
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
--
Dave Manuals@ArtekManuals.com www.ArtekManuals.com
--
This email has been checked for viruses by Avast antivirus software.
https://www.avast.com/antivirus
_________________
Searchable Archives: http://www.contesting.com/_topband - Topband Reflector
|