Mike,
Tuned radials are really not needed in an elevated radial setup.
You just put an ATU at the base of the vertical section and run 2-4
radials from the ground of the ATU. The only issue is making sure the
antenna system is really high enough to be called raised. I would shoot
for elevations in excess of 1/10 wavelength, and preferably a bit more.
Impedance of the antenna is totally unimportant as the ATU takes care of
making sure your transmitter "sees" a proper load.
73,
Barry
K3NDM
On 7/1/2013 12:49 PM, Mike WA8BXN wrote:
Randy,
I think elevated radials need to be tuned, that is a particular length for a
given band. If you will be operating multiple bands, a set is needed for
each band. Radials on or under ground do not need to be a particular length
to work (more and longer is probably always good).
What band(s) do you want to operate? If 20 meters, you might consider an end
fed half wave vertical that would not need much ground system.
73 - Mike WA8BXN
-------Original Message-------
From: Randy Cook
Date: 07/01/13 12:30:28
To: [email protected]
Subject: [Elecraft] OT- Radials for Vertical Antenna
I would appreciate any help from the group on my unusual antenna situation.
Not really Elecraft related, so OK to respond off line.
Recently, we had to gut our back yard, as several Redwood trees were
undermining a retaining wall. Bad situation. So, the trees had to go, and
with them my antenna supports! I now have essentially a 50ft by 30ft yard
with 6ft fences on the three sides, house and porch on the fourth. Some
hardscape prevents long radials. For aesthetic reasons, I don't have a tower
or tall supports. My first shot was a fiberglass pole, at about 34ft, with a
wire up the middle. Terminates in the base to an MFJ antenna autotuner. I
placed the pole a few feet from the corner of the lot where, when painted,
blends into a neighbors tree behind, and is an barely visible from the
street.
My limitations are the radial field. I did some research, and started with 8
wires, varying from 15' to 35' in a 100 degree spread on the flower beds and
small lawn. Another ham suggested elevated radials as an alternative, so I
tried two 35' radials at 90 deg angles along two fence sides, about 4' off
the ground. Much of what I read was from hams with big lots and dozens of
radial in all directions. Couldn't find much on my situation.
Conditions have not been that good, and other commitments have prevented
much testing. I have some time now and want to find the best solution.
Questions for the group--
Give the limits on the radial field (90-110 degrees, limited length) is 10
buried better than 2 elevated?
Does it make sense to use BOTH elevated and buried?
Some prelim testing, using some SE Asia DX stations, showed little
difference in the receive signal strength switching in either or both radial
plans. I plan on using some on air events this week to gather signal
strength reports on my transmissions.
Any thoughts?
73
Randy Cook - K6CRC
K3 #2051
[email protected]
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