06-06-2001, 03:17 PM
Arnie Coro CO2KK (arnie@rhc.cu) writes "Hi all 6 meter enthusiasts and prospective users of the magic band !
Got a phenomenal response from my posting about the ASD antenna...
Yes the wire antenna that has already allowed me to work
Transatlantic to Spain and Africa , plus South America and
lots of Sporadic E...
The tremendous interest generated led me to explain a bit more
in detail here how the antenna is made... and also warn antenna
gurus that modelling software does not seem to do very well
with it...
The antenna has a set of three 1/4 wave elements fanning out
at about 30 degrees at the top end, that's the end near to the
mast. I separated the antenna's end insulator by a good 1/4
wave length from the mast...
The antenna feedpoint has a choke coil balun installed...
I use RG8X cable, and six turns around a 4 inch or 100 mm
diameter water PVC pipe does the job beautifully.
The LONG SIDE of the antenna can be 3/4, 5/4 , 7/4 or 9/4
wavelengths long...
The antenna slopes down at an angle between 20 and 40 degrees...
At the end of the sloping element there is an insulator, and
I have added there 5 1/4 wave radials that fan out from the
end insulator, to make a better ground plane...
There is something important... the antenna has to be sloping
in the general direction you want to work... That's why I use
three of them , one to South America, one to Europe, and one
to the Center of North America... After the F2 season and the
Summer Es season are over, the Europe ASD is moved to Eastern
North America, and the Center North America is moved more
to the West...
The other thing you may want to add is a RESISTIVE TERMINATION.
That will turn the antenna into an ASTD or Assymetric Sloping
Terminated Dipole... The value of the terminating resistor is
optimized at 240 ohms, but tests show that values between
200 and 400 ohms work very well... The resistor must be NON INDUCTIVE
and capable of dissipating about 20 percent of the output power
Keep the coaxial cable at 90 degrees to the axis of the antenna
and make your coaxial cable run an even number of half wavelengths
taking into account the velocity factor of the cable...
The ASD for 6 meters is a rather TOA antenna ( TOA= Take Off Angle )
but it does seem to have a minor , but significant lobe,at about
30 degrees, which proves to be a nice feature for working very
short E skip...
Please notice that the following 5 weeks are the best ones of
the year to work via Sporadic E... So go ahead and install your
ASDs .... and enjoy 6 meters...
An antenna tuner is a ESSENTIAL when using the ASD with solid
state radios...
73 and DX
Be listening on 6 here whenever at my home QTH
Arnie Coro
CO2KK
arnie@rhc.cu
arnie@radiohc.org"
Got a phenomenal response from my posting about the ASD antenna...
Yes the wire antenna that has already allowed me to work
Transatlantic to Spain and Africa , plus South America and
lots of Sporadic E...
The tremendous interest generated led me to explain a bit more
in detail here how the antenna is made... and also warn antenna
gurus that modelling software does not seem to do very well
with it...
The antenna has a set of three 1/4 wave elements fanning out
at about 30 degrees at the top end, that's the end near to the
mast. I separated the antenna's end insulator by a good 1/4
wave length from the mast...
The antenna feedpoint has a choke coil balun installed...
I use RG8X cable, and six turns around a 4 inch or 100 mm
diameter water PVC pipe does the job beautifully.
The LONG SIDE of the antenna can be 3/4, 5/4 , 7/4 or 9/4
wavelengths long...
The antenna slopes down at an angle between 20 and 40 degrees...
At the end of the sloping element there is an insulator, and
I have added there 5 1/4 wave radials that fan out from the
end insulator, to make a better ground plane...
There is something important... the antenna has to be sloping
in the general direction you want to work... That's why I use
three of them , one to South America, one to Europe, and one
to the Center of North America... After the F2 season and the
Summer Es season are over, the Europe ASD is moved to Eastern
North America, and the Center North America is moved more
to the West...
The other thing you may want to add is a RESISTIVE TERMINATION.
That will turn the antenna into an ASTD or Assymetric Sloping
Terminated Dipole... The value of the terminating resistor is
optimized at 240 ohms, but tests show that values between
200 and 400 ohms work very well... The resistor must be NON INDUCTIVE
and capable of dissipating about 20 percent of the output power
Keep the coaxial cable at 90 degrees to the axis of the antenna
and make your coaxial cable run an even number of half wavelengths
taking into account the velocity factor of the cable...
The ASD for 6 meters is a rather TOA antenna ( TOA= Take Off Angle )
but it does seem to have a minor , but significant lobe,at about
30 degrees, which proves to be a nice feature for working very
short E skip...
Please notice that the following 5 weeks are the best ones of
the year to work via Sporadic E... So go ahead and install your
ASDs .... and enjoy 6 meters...
An antenna tuner is a ESSENTIAL when using the ASD with solid
state radios...
73 and DX
Be listening on 6 here whenever at my home QTH
Arnie Coro
CO2KK
arnie@rhc.cu
arnie@radiohc.org"