Discone Mounted Upside Down?
Frank Donovan
There are many types of conical antennas, the discone being an example of
a very efficient broadband conical vertical. As you correcty point out,
a discone has the disk at the top! Several manufacturers, such as TCI
and Granger sell cone antennas that may match the brief description you
provided. Their theory of operation differs from the discone, and they
are probably somewhat less efficient.
73!
Frank
W3LPL
dono...@sgate.com
On 27 Aug 1995 Gary_...@Cyberstore.NET wrote:
> Hi
>
> I recently drove past a building in town with what looks like a discone on
> the roof. It appears to be mounted upside down. The 'disk' being at the
> bottom and the open end of the cone at the top.
>
> I'm just curious whether this has any effect on performance.
>
> ..Gary
Gary_...@cyberstore.net
Roger A. Cox
Sometimes inverted discones are constucted at HF because of their
size. I assume that since it is on a roof, it probably is VHF or
possibly above 20 MHz.
In HF inverted-discones, they are usually mounted on the ground
with the disc part forming the ground radials. The cone part is
a broadband monopole, which sometimes looks like a HUGE bicycle
wheel suspended from a central tower. I have seen these operate
from 3 to 30 MHz, broadband.
73, Roger WB0DGF
Bruce Forestal
: Gary,
: There are many types of conical antennas, the discone being an example of
: a very efficient broadband conical vertical. As you correcty point out,
: a discone has the disk at the top! Several manufacturers, such as TCI
: and Granger sell cone antennas that may match the brief description you
: provided. Their theory of operation differs from the discone, and they
: are probably somewhat less efficient.
: 73!
: Frank
: W3LPL
: dono...@sgate.com
: On 27 Aug 1995 Gary_...@Cyberstore.NET wrote:
: > Hi
A discone antenna makes a good all around scanner antenna. The FAA has used discones at airports for
many years. One discone will cover 118 to 136 Mhz and 200 to 350 MHz and have a fairly low VSWR.
As you go up in frequency the relative size verses the wavelength becomes larger and you get higher
gain but the radiation angle also goes up. "Radiation Angle" is the angle above the horizon where
the antenna has the highest gain. For most scanning the signals are on the horizon so you want a
radiation angle at zero degrees, ie parallel with the horizon. A discone at low frequencies has an angle just above the horizon as you go up in frequency this angle will also go up. By mounting the
discone upside down you will have the greatest gain below the horizon for better penetration
into the buildings.
Bruce :-)
fore...@sdds0.hac.com