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*To*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Subject*: Re: [TCML] Tesla Coil + Transmitting Antenna ?*From*: paul <tcml88@xxxxxxxxxxx>*Date*: Thu, 07 Jun 2012 11:01:46 +0000*Delivered-to*: teslaarchive@xxxxxxxxxx*Delivered-to*: tesla@xxxxxxxxxx*In-reply-to*: <4FD02107.8020805@xxxxxxxxxxxxx>*List-archive*: <http://www.pupman.com/pipermail/tesla>*List-help*: <mailto:tesla-request@pupman.com?subject=help>*List-id*: Tesla Coil Mailing List <tesla.pupman.com>*List-post*: <mailto:tesla@pupman.com>*List-subscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=subscribe>*List-unsubscribe*: <http://www.pupman.com/mailman/listinfo/tesla>, <mailto:tesla-request@pupman.com?subject=unsubscribe>*References*: <3F5A22145E63410598266E01C7A8C458@johnmorelandPC> <1338925422.7339.YahooMailNeo@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> <4FCEAD50.1070201@xxxxxxxxxxx> <4FCEDB3C.5080904@xxxxxxxxxxx> <1339011882.57727.YahooMailNeo@xxxxxxxxxxxxxxxxxxxxxxxxxxxx> <4FD02107.8020805@xxxxxxxxxxxxx>*Reply-to*: Tesla Coil Mailing List <tesla@xxxxxxxxxx>*Sender*: tesla-bounces@xxxxxxxxxx*User-agent*: Mozilla/5.0 (X11; U; Linux i686; en-US; rv:1.9.2.28) Gecko/20120313 Thunderbird/3.1.20

Miles Waldron wrote: > I have always wondered if the secondary of a tesla coil > has any interesting antenna properties, ... > ... I believe, ... the length of the secondary tube, not the > length of the wire wrapped around the tube, would be the > interesting variable. It's the height of the topload that matters the most. The TC (with topload) is very small compared to the free space wavelength so is accurately represented as a Hertzian dipole and a Hertzian current loop. The only significant parameters concerning radiation are its operating frequency, and electric and magnetic dipole moments. The two dipole moments, which represent independent radiation mechanisms, in turn depend only on the topload height and capacitance, top voltage, secondary cross-section area, number of turns, and secondary current. The electric dipole dominates the far field radiation for normal Tesla coil dimensions. Leaving out all phase factors, De = electric dipole moment = omega * Ctop * Vtop * h omega = 2 * pi * frequency; h = topload height; Ctop = topload capacitance; Vtop = top voltage; and then the vertical far-field volts/metre at low elevation at a range r is Ev(r) = omega * mu * De / (4 * pi * r); mu = 4 * pi * 10^-7; The actual Ev(r) could be up to twice this depending on the Fresnel reflection coefficient of the ground, and there might also be a small ground wave component (the formula for which is complicated). The source for the magnetic dipole is the coil current times the number of turns N, times the cross-section area A of the secondary, Dm = magnetic dipole moment = omega * mu * Isec * N * A; Isec = secondary current; and this produces a vertical magnetic far-field, at low elevation, of Hv(r) = omega * epsilon * Dm /(4 * pi * r); epsilon = 8.854 * 10^-12; This component doesn't propagate very well at all because of the strong attenuation of the associated horizontal E-field. At some distance (more than a km or so) the field is dominated by Ev and its associated horizontal H-field of Ev/377 Amps/metre. -- Paul Nicholson -- _______________________________________________ Tesla mailing list Tesla@xxxxxxxxxx http://www.pupman.com/mailman/listinfo/tesla

**Follow-Ups**:

**References**:**[TCML] question***From:*greg westfall

**Re: [TCML] question***From:*Matt Siri

**Re: [TCML] question***From:*ED

**[TCML] Tesla Coil + Transmitting Antenna ?***From:*miles

**Re: [TCML] Tesla Coil + Transmitting Antenna ?***From:*Matt Siri

**Re: [TCML] Tesla Coil + Transmitting Antenna ?***From:*Jim Lux

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