Committee on Radio Astronomy Frequencies


Estimate of maximum acceptable e.i.r.p. of terrestrial transmitter without causing interfering to a radio astronomy station using free space propagation


This routine calculates the maximum acceptable e.i.r.p. of terrestrial transmitters that must be respected to protect the Radio Astronomy Service using a free space propagation model given in Recommendation ITU-R P.525 while to estimate the atmospheric attenuation, Recommendation ITU-R P.676 is used.
This routine can also be used to estimate the separation distance between the transmitter and the radio astronomy station for an aggregate of transmitting devices. In this, calculations are done for different minimum distance values until the maximum tolerable e.i.r.p. is reached.

The calculation uses the geographic summation methodology. Since a generic solution is anticipated, no terrain model is included.

The protection criteria for Radio Astronomy is given in Recommendation ITU-R RA.769.
The tolerable data loss to radio astronomy observations and percentage-of-time criteria resulting from degradation by interference for frequency bands allocated to the radio astronomy on a primary basis are given in Recommendation ITU-R RA.1513.


maximum permissible spectral power density: (in dB(Wm-2Hz-1))
frequency: (MHz)
allocation bandwidth: (MHz)
density of active users transmitting towards the victim station: (km-2)
minimum separation distance (>= 0.001 km): (in km)
air pressure: (in hPa)
temperature: (in oC)
water vapour density: (in g/cm3)
maximum radius of rings: (in km)
ring width: (in km - the accuracy of the results depends strongly on this number)
number of mobile systems:

Fill in and click to get results
or click reset to renew all parameters


Last modified: December 03, 2004