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

To: "'W2RU - Bud Hippisley'" <>, <>
Subject: Re: [TowerTalk] Using an iPhone App to line up your antenna
From: "Dick Green WC1M" <>
Date: Wed, 4 Jan 2012 17:42:23 -0500
List-post: <">>
I thought the iPhone 4 and 4s have special hardware for the compass function
and the 3G does not. Is that true?

73, Dick WC1M

--Original Message-----
From: W2RU - Bud Hippisley [] 
Sent: Wednesday, January 04, 2012 3:38 PM
Cc: TowerTalk topics. and HF antenna construction;
Subject: Re: [TowerTalk] Using an iPhone App to line up your antenna

 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


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