[BC] Directional Antenna Proofs

[Mike McCarthy]

James,

Get a FIM and run the radials.  Put an end to the speculation.  If in 
doubt about the main lobe run the main lobe radials out to 50 miles and 
then put them on an inverse distance chart showing the theoretical 
curves for the conductivity in that area. Only if they don't match the 
original proof and/or they are off from the theoretical by some amount 
should you go digging for problems in the ground system.

Then if you can, get a spectrum analyzer and look at the spectrum 
envelope.  Are your sidebands symmetrical or is there tilt?

Also, look at the transmitter with a scope and create the trapezoid 
image of a demodulated envelope.  Anything except a perfectly flat and 
sharp image angle on both sides indicates a potential problem.

Also, verify the match symmetry and rotation of the match. That will 
have a profound impact on loudness, especially if the array has narrow 
bandwidth. That could be a significant issue if the station was loud 
with tube box and not with a solid state TX.

While the ground system is important and can have as much as a 6dB 
impact, the comment's you're making infers something more significant.  
Significant enough that 6dB would be at the low end of the degradation 
range.

MM

On 6/20/2012 11:13 PM, James B. Potter wrote:
> Mike:
>
> Thanks for your remarks.  I have considered the likelihood that the ground
> radials have corroded.
>