Post by Deleted on Apr 13, 2017 3:52:58 GMT
Putting To Rest All Discussion of "Long Ground Leads"
After sifting these conversations about "long ground leads" over the years, I would like to propose that no one as yet has actually reduced the conversation to its most basic components.
Allow me.
An elevated AM 3-meter antenna with a vertical wire attached to the transmitter ground and stretching down to the earth is a very unbalanced dipole antenna.
It is unbalanced in three ways.
Being by definition a balanced circuit, a dipole antenna is mismatched to the transmitter which typically has an unbalanced RF output.
The technically proper way to match an unbalanced RF output to a balanced dipole antenna would be the use of a transformer,
If the transmitter were raised 3-meters off the ground with a 3-meter wire attached to the ground side of the transmitter and reaching to the ground and had a 3-meter antenna rising vertically above the transmitter the dipole would be balanced through being symetrical, but the total antenna length would become 6-meters, violating 15.219. Attaching the earth end of the dipole to a ground rod would extend the lower reach of the antenna another 8-feet into the earth, accomplishing another form of mismatch to the antenna.
There is no proper dipole antenna that sinks one end into the earth.
The best one could do with a dipole under 15.219 would be 1.5-meter vertical wire on the ground side of the transmitter and a 1.5-meter vertical wire on the antenna. Mounting at any altitude would be possible with no electrical earth ground.
After sifting these conversations about "long ground leads" over the years, I would like to propose that no one as yet has actually reduced the conversation to its most basic components.
Allow me.
An elevated AM 3-meter antenna with a vertical wire attached to the transmitter ground and stretching down to the earth is a very unbalanced dipole antenna.
It is unbalanced in three ways.
Being by definition a balanced circuit, a dipole antenna is mismatched to the transmitter which typically has an unbalanced RF output.
The technically proper way to match an unbalanced RF output to a balanced dipole antenna would be the use of a transformer,
If the transmitter were raised 3-meters off the ground with a 3-meter wire attached to the ground side of the transmitter and reaching to the ground and had a 3-meter antenna rising vertically above the transmitter the dipole would be balanced through being symetrical, but the total antenna length would become 6-meters, violating 15.219. Attaching the earth end of the dipole to a ground rod would extend the lower reach of the antenna another 8-feet into the earth, accomplishing another form of mismatch to the antenna.
There is no proper dipole antenna that sinks one end into the earth.
The best one could do with a dipole under 15.219 would be 1.5-meter vertical wire on the ground side of the transmitter and a 1.5-meter vertical wire on the antenna. Mounting at any altitude would be possible with no electrical earth ground.
