Topband: Define "near"

[Tom Rauch]

> winter beverages, I need to come up with an alternative (need it for
> summer anyway). I have been looking at the K9AY as a possibility, but
> I have noticed several commments about making sure it isn't near my
> transmitting antenna. The various sources, however,  have neglected to
> comment on what, exactly, 'near' means. How close is too close?

Here at my QTH, a 4-element array of short RX verticals (a K9AY is 
really the electrical equivalent of two short verticals phased with a 
open feed wire) has noticeable deterioration of pattern when beamed 
southwest towards my TX vertical array (about 250 or 300 feet away). 
I just checked F/B ratio on W1AW, and it goes from about 30-40dB to 
only about 10dB when I do not detune the TX antennas. 

Another tower puts a substantial null (several dB) in my TX array 
unless detuned, and that is at a spacing of  500 feet. That means it 
would distort the pattern of a vertical polarization responding RX 
antenna in the a similar manner at the same distance.

The problem is significantly reduced when the RX  antenna beams away 
from the TX antenna. The best advice is don't aim the RX antenna 
through or even near the TX antenna if you can help it, otherwise you 
might have to detune the TX antenna when receiving.        73, Tom 
W8JI
W8JI@contesting.com