Re: [IRCA] calulating AM directional ERP when field strengths known?

[Deane McIntyre <dmcintyr@xxxxxxxxxxx>]

On 2011-05-16, at 9:09 PM, Stephen Airy wrote:

> Hi all...
>  
> Does anyone know how to calculate the effective radiated power (or whatever is the correct term) for an AM directional station along a particular heading?
> Using 1170 KCBQ as an example, I know:
> the actual transmitter power (50kW),
> the RMS field at 1 km (2,499.50 mV/m - assuming it's operating non-directional - found this in the FCC database)
> the field at 1km in a particular direction (3,750 mV/m - estimating/interpolating between the 185° 3559.01mV/m and 190° 3935.08mV/m - actual heading is 187.3°)
>  
> 

ERP = xmtr power x (field at 1km /RMS field at 1 km)^^2

In your example. 50 kW x (3750/2499.5)^^2
= 50 kW x 2.251
= 112.5 kW ERP

73,

Deane McIntyre
VE6BPO
> 


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