[BC] am receiver for monitoring at a 20 KW site (add)

[RichardBJohnson at comcast.net]

At a transmitter site, the RF voltage from the primary radiator may be tens of VOLTS per meter! The approximate formula ls:
E = 300/r * sqrt(P*G*A), where r is the distance to the radiator in meters, P is the power in kW, G is gain relative to a dipole, and A is the "ground" factor, typically 0.90. So, you can see that at 1 meter from the antenna, the signal is about 300 volts/meter for 1 kW and it drops off linearly with distance. 

That is why shielding is everything and my scheme of a loop antenna inside the shield,  coupled to a loop antenna outside the shield is about the only thing that can be counted upon to work right near transmitter towers.

Cheers,
Richard B. Johnson
Book: http://www.AbominableFirebug.com/

----- Original Message -----
From: seibold at trainride.com

I should add that both the R-390A and HRO were revered intercept receivers; there were thousands of HROs in WW II intercept service "digging out the weak ones" with less than half the tubes and a tenth of the mechanical complexity of the R-390A.