The radio noise spectrum from e.l.f. to e.h.f.

JournalofAtmospheric andTerrestrial Physics,1966,vol. 28, pp.429-430.PergamonPressLtd. Printedin NorthernIreland

SHORT PAPER

The radio noise spectrum from e.1.f. to e.h.f. WM. H. FISCHER National Center for Atmospheric Research, * Boulder, Colorado, U.S.A. (Received

Abstract-This

1965)

note corrects the Author’s earlier paper (1965) J. Atmosph.

The Author’s (FISCHER,

2 November

paper entitled

Terr: Phys.

27,475.

“The radio noise spectrum from e.1.f. to e.h.f.” in two respects as follows. Both the corrections

1965) needs to be corrected

apply to p. 479. 1. It should be added that HORNER (1960) states that a half-wave length horizontal dipole antenna one-quarter-wavelength above the ground, such as COTTONY and JOHLER used, integrates the noise from the whole of the visible hemisphere, except for directions nearly in line with the antenna. Changes in the orientation and height of the antenna (provided that it is at least $A above the Earth) do not greatly affect the average noise. 2. Figure 2 is in error, and should be replaced by Fig. A which exhibits the WAVE LENGTH

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FREOUENCY

Fig. A. The radio noise spectrum. * Operated by the University Corporation for Atmospheric Research under contract with the National Science Foundation. 429

430

WM.

H. FISCHER

fact that beyond a few Gc/s, noise arises in the atmosphere of the Earth due to absorption by oxygen, water vapour and rain (HOW and MUMFORD,1960). This energy causes the atmosphere to emit black body radiation whose magnitude is a complex function of the composition. The continually decreasing contribution from galactic noise, coupled with the above mentioned emission, results in a minimum in received radio noise at about 6 Gels, followed by a sharp rise in received radio noise intensity as the antenna takes on the ambient air radiation temperature. The water content of the atmosphere in all its forms and the antenna pattern will have major effects upon the noise received in this frequency region. REFERENCES FISCHERWM. H. Hoao D. C. and M~ORD HORNERF.

W. W.

1965 1960 1960

J. Atmmph. Terr. Phye. $27, 475. Mkxvwave J. S, 80. Proc. Imtn. Elect. Eqp. lW'B,373.