[Lf] LF: Radiated powers ...]

[Andre' Kesteloot]

Väinö Lehtoranta wrote:

> For those interested on the history of LF/MF coverage planning:
>
> (An excerpt from a report of
> EBU Working Party A, Hamburg, April 1971)
>
> DEFINITIONS OF RADIATED TRANSMITTER POWER
> -- (5 proposals received) --
>
> a)  Effective radiated power (ERP) - by ORF (J. Burgstaller)
>
> It is proposed to apply the same definition as the one
> used in the VHF and UHF bands.
>
> b)  Equivalent monopole radiated power (EMRP) - BBC (Dr Phillips)
>
> This definition is based on a short vertical reference aerial,
> giving horizontally the same radiation as the actual aerial,
> both being assumed to be located on a perfectly-conducting
> horizontal plane. The advantage would be that in the present
> CCIR Report, the curves would correspond to 1 kW EMRP (!!!)
>
> c)  Equivalent power at a distance of 10 km (EP) - RTE (Mr Curley)
>
> For MF propagation it would be reasonable to consider the
> surrounding countryside up to a radial distance of approximately
> 10 km as being part of the aerial system. A practical suggestion
> to define the radiated power may be as follows: the equivalent
> power required to produce the same field strength at 10 km when
> applied at the base of a vertical aerial of one quarter wavelength
> equipped with a perfect earth system and moderate conductivity
> (3*10E-3 mhos/m) around that aerial up to a distance of 10 km.
>
> d)  Cymomotive force (CMF) - ORTF
>
> The cymomotive force is defined at any point in the space around
> an aerial, for which the fed-in energy is known, related to the
> distance of that point from the aerial. The gain of the aerial
> must be considered when the field strength is calculated at that
> point. The product of the field strength and the distance
> is defined as the cymomotive force.
>
> e)  Operative radiated power (ORP) - ARD/ZDF
>
> This term is defined as follows: "The power supplied to the
> antenna multiplied by the gain of the antenna in a given direction
> when the reference antenna, placed on the surface of a perfectly
> conducting plane earth, produces an unattenuated field strength
> of 300 mV/m at a distance of 1 km at any angle of departure
> above the plane earth.
> ----------------------------------------------------------------
> Note by Vaino:  ERP also was there but it was not supported...
>
> At 03:08 17.4.2000 -0400, Geri wrote:----------------------
> >Hello Dick,
> >
> >great that you also made your field strength measurements.
> >
> >>we find at Puckeridge 45W was fed to the aerial on 136kHz and 7.5W on
> >73kHz.
> >
> >The difference between your findings and mine (16 W ERP on 73 kHz, measured
> >at nearly twice the distance using a very basic and rough "rule of thump"
> >measurment) is only about 3 dB.
> >
> >Dick, PA0SE wrote:
> >
> >>This is EIRP and not ERP of course.
> >
> >Well, kind of. What I thought was a silly question seems seems always to
> >have been a point of discussion betwen the experts. Let me quote from an
> >e-mail that Vaino, OH2LX has send me as an answer to my question:
> >
> >>We have not been using the "paper curves" for some time.
> >>Many computer GW programmes have been developed but none of
> >>them seem to serve us the way we all should expect them to do.
> >>
> >>Hardly no one was serious with either ERP or EIRP when the
> >>"Conditions of validity" for the family of curves were being
> >>formulated. There were some 6 or 7 candidates icluding CMF,
> >>EMRP and some others. EIRP is rather "fuzzy" and ERP refers
> >>to a dipole, so the choice was to be called EMRP:
> >>
> >>- The radiating element is a short vertical monopole
> >>  (The equivalent dipole moment is 5(lambda)/2(pii)). Assuming
> >>  such a vertical antenna to be on the surface of a perfectly
> >>  conducting plane earth and excited so as to radiate 1 kW,
> >>  the fiels at a distance of 1 km would be 300 mV/m;
> >>  this corresponds to a cymomotive force of 300 V.
> >>
> >>Personally I don't know anyone who wants to make practical
> >>field work or reporting in terms of CMF. As you know from
> >>practice, the problems are hiding elsewhere. Usually it is
> >>most useful to discover a lump sigma value for a ground path
> >>with potential adjustments according to seasonal etc conditions.
> >>Without reliable looking long term measurements with supporting
> >>occasional flight measurements there would be no brain twisting,
> >>at least we could not explain all what happens on measurements.
> >
> >Best 73   Geri, DK8KW (W1KW)
>
> ----------------------------------------------------------
> V.K.Lehtoranta, OH2LX, POBox 50, FIN-05401 Jokela, Finland
> ------ Tel: +358-9-4173965 ---- Fax: +358-9-4173961 ------
> E-mail: vaiski at dlc.fi - alias: oh2lx at dlc.fi & oh2lx at sral.fi