[TowerTalk] Using an iPhone App to line up your antenna

[W2RU - Bud Hippisley]

 On Jan 4, 2012, at 2:57 PM, Gary Schafer wrote:

> That sounds like an invitation for an owl to come and crap on the iphone. 
> 
> 73
> Gary  K4FMX


I don't know about that owl, but *I'm* going to.

I have a freebie compass app on my iPhone 3Gs.  It's called (believe it or not) "Compass".  I've typically only used it in locations where I had no idea what the actual bearings might be, so I never checked its accuracy.

Recently I used it to check the alignment of something on my property and found, to my dismay, that it wasn't very accurate at all!  

When I tested it by standing reasonably far from my house and my tower and guy wires, in line with an E-W wall, and then stood in a second place, in line with a N-S wall, the readings from my app were only about 40 or 50 degrees different from each other!

So I re-did the measurements with my trusty old-fashioned floating magnet compass you can buy in any outdoor equipment store, while standing in the same two locations.  It was as close to 90 degrees difference in the two readings as I could eyeball.

I know from Google Earth satellite views what the actual bearings of my walls are.  It is very clear that the compass app was in serious error.

The only calibration procedure that I'm aware of for this app is to wave the phone around in figure 8s.

Perhaps there is something about the magnetic sensors in the iPhone that make it substantially more sensitive to nearby metal than the traditional camping compass but, if so, that makes it useless for virtually every purpose I have for using it.

Bud, W2RU