[TowerTalk] SO2R or Multiop Contesting without

[jimlux]

On 5/29/18 10:06 AM, Ed Sawyer wrote:
> I have 2 towers separated by 140 ft.  Monobanders.  The towers are running
> roughly N/S so I am not fully pointing at one when beaming EU but its not
> "tip to tip" either.
> 

Keeping this "antenna" related - 140 ft is 2 wavelengths on 20m.  On the 
lower bands, you're substantially less than wavelength apart, so the 
interaction is probably predominantly "near field" - that might make the 
pointing direction irrelevant.  The distribution and direction of the 
electric and magnetic fields (esp if there's significant directive gain) 
may be substantially different from what's in the far field.

Tip to tip, 90 degrees, or some other configuration might be the "worst 
case".

Are your monobanders 3 elements, or more elements?  More elements 
implies more stored energy (larger amplitudes) in the near field.




>   
> 
> Some of the newer rigs, using many stages of pre-amps on an SDR seem to be
> more susceptible for this than others.

Probably depends on the front end selectivity - a lot of SDRs run a sort 
of "wide open" front end, and get their ultimate selectivity in 
software.  Which doesn't help if you're getting IMD in the front end or ADC.