Sunday, December 28, 2008

PHG antenna direction plotting

Last night I figured out the math to plot nice cardioid patterns, and this morning I finally got the rotation right, so now the PHG plotting shows the directivity parameter, too. It's been requested by quite a few users since I got the circles going.

The first image shows a PHG plot with an omni pattern (no directivity), and the second image shows a PHG plot with a directional antenna pointing at 135° (southeast). Please bear in mind that these plots describe very rough approximations and best guesses about the station's service range.

You can generate a PHGR comment extension for your digipeater or igate using the PHG calculator. Please monitor your station's receiver performance and adjust the PHG settings to match the observed range.


Anonymous said...

Correct me if I'm wrong but shouldn't your cardioid pattern heart points meet at the actual object and not "radius/2" distance behind it?

oh7lzb said...

Anonymous: Maybe, if your antenna would have an absolute null behind it, and would not receive anything from the behind. Many antennas don't have one. Many directional antennas have a significant lobe right behind them and nulls on the sides of the back lobe.

Please remember that this is a very, very rough approximation of real antenna performance - we're not trying to do real antenna radiation pattern modeling here, since we don't have enough information to do such analysis.

VE6SRV said...

Okay, now I need another tool... those lovely PHG circles can get a little overlapped here and there. I don't know if you can have a tooltip or something similar pop up when over a PHG circle, so that one can identify which circle belongs to which station. That might be a bit tough, especially when 4 or 5 circles all overlap. What about a way of highlighting the PHG circle when hovering over the station that generates the PHG circle?

Southern British Columbia gets a little busy when the PHG circles pop up. Sometimes I'd like to find the station that plots the PHG circle, but it's tough to find the center of that circle.

Any brainy ideas?

Anonymous said...


it seems that the 'R' in 'PHGR' is missing

73 Chris PA7RHM

oh7lzb said...

I've now implemented the 'R'. It was parsed and stored in the database, but I had forgotten to show it on the map.