Re: Counterpoise and MMC demise

["Tesla list" <tesla-at-pupman-dot-com>]

Original poster: "Ed Phillips by way of Terry Fritz <teslalist-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
 >
 > Original poster: "davep by way of Terry Fritz <teslalist-at-qwest-dot-net>" 
<davep-at-quik-dot-com>
 >
 > >>A rule of thumb for designing vertical broadcast antennas
 >
 > >>is that the there is little benefit in having a
 >
 > >>counterpoise whose RADIUS is equal to the height of the
 >
 > >>antenna.
 >
 >          The rule given in (eg Antenna Engineer's Handbook
 >          Jasik, others) is that radials should be about
 >          1/4 wave long, which is roughly the tower height in
 >          many cases.  The same maybe observed in CB and
 >          scanner antennas...
 >
 > >>I can't see why this shouldn't be at least as applicable to TC's.
 >
 >          Broadcast practice is designed for radiation.
 >          Tesla Coils commonly are not.
 >          8)>>
 >          And a 1/4 Wave at (say) 150 KHz is 'interesting'.
 > --
 >          best
 >          dwp

	Most BC stations use towers higher than 1/4 wave in order to control
the vertical radiation angle and put more power where it does some good;
5/8 wave towers are great if you can afford them.  Counterpoises
(elevated conductors above ground) are used to minimize losses due to
ground resistance.  Laport's book "Radio Antenna Engineering" gives
curves of radiation efficiency as a function of the number of "radials"
which shows diminishing benefits beyond about 4, although commercial
stations use many more, but those are in contact with more or less
conducting earth.  As for TC's I still think that a counterpoise radius
equal to the height should be more than sufficient.  Larger is better of
course, but this is only a hobby.

	At 150 kHz 1/4 wave is ~1640 feet!

Ed