[TowerTalk] EH Antenna - or when is a shield not a shield?
chief at thechief.com
Fri Nov 11 13:02:16 EST 2005
>Actually Ted Hart, who claims to be the inventor of the EH
>antenna, gave a stern warning to never use common mode
>chokes on the feedline of EH antennas because it stops the
>system from working. What Hart actually said was:
>"If you use RF beads, since the coax shield is not a
>magnetic shield, the beads affect both the inner and outer
>conductors. Therefore, most of the transmitter power will be
>converted to heat. Not good."
>He also said:
>"RF on the Coax
>Due to the large radiation at the EH Antenna, there will be
>some RF coupling to the coax. Whether this is a problem is
>dependent on the radio you use. Some are subject to RF
>coupling into the audio system, which causes severe
>distortion while transmitting. On some field day setups with
>100 watt transmitters we have had so much RF on the radio
>you can get an RF burn. Below we have suggested ways to
>eliminate the RF coupling problem."
Yes, these fringe ideas stick around because the theory always looks
reasonable, except for an innocuous looking but terribly fatal flaw. In
"...the beads affect both the inner and outer conductors."
Not only is this totally bogus but the justification for this bogosity is
found by reading between the lines of the following:
"Therefore, most of the transmitter power will be converted to heat. Not
To which I would add: (Yes, not good because all that heat represents what
would have been fierce feedline radiation. Without that the antenna by
itself doesn't work as he rightfully asserts in the first paragraph.)
What motivates an otherwise intelligent person to say something like this?
Perhaps the answer can be found in his support of the Kor Radiation theory.
Dudley - WA1X
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