[aprssig] Omni DFing...

[Jason Winningham]

On May 11, 2006, at 11:01 PM, w0ep wrote:

> I understand having people say "I hear that bad boy at X strength here
> in BugTussle"
>
> I don't understand at all what that has to do with my power output
> nor how APRS fits in the picture except as a way to do the mapping.

The theory is that if you already know your antenna height and gain  
(two out of three in PHG), all you need for a complete "omni DF  
report" is the signal strength.  If you are transmitting that in your  
APRS position report and you are listening with the same antenna as  
your APRS rig, you use the same height/gain values for both PHG and  
the omni DF object.

To take it a step further, even if you don't remember your HG, someon  
plotting DF objects based on you voice report can use the PHG info  
that you are beaconing combined with your  "I hear that bad boy at X  
strength here in BugTussle" report.

All this hinges on

  - you supplying correct values for H/G
  - the formula to derive range from H/G being correct
  - you living on a perfectly spherical planet (:

OK, that last one was a little bit of exaggeration, but PHG does  
little to allow for terrain features, e.g. situations such as your  
station being at the foot of a mountain, where coverage would be  
roughly a semicircle.

-Jason
kg4wsv