Ham Tracker on the iPhone

I read about this iPhone application on the South Yorkshire Repeater Group website. APRS using the mobile phone infrastructure.
For a quick test of it today I set it going and shoved the phone back in my pocket. A check on aprs.fi when I got home showed it worked well, accurately tracking my route. For more info the developers website is www.kramstuff.com and it is in the App. store. Version 1.2 is due soon with more battery saving options, choose APRS symbol and to allow comments to be sent with your position reports.
I hope to try it out on a proper walk when I get chance, snow and family permitting.

In reply to G1RVK:

Only problem with iphone apps is the battery limitation. The other aprs app i have tried is “iBCNU” it was free but i believe it is a paid for app now. Worked well the times i used it.



In reply to G1RVK:
The only one I have downloaded is http://www.openaprs.net/ but I haven’t really had time to set it up properly and try it out.

Ham Tracker looks interesting, I will give it a go.
Roger MW0IDX

In reply to G1RVK:

Several new customers today have mentioned that they heard about Ham Tracker via this reflector, so I thought I’d pop in to say thanks for the mention.

Regarding Ham Tracker’s battery saving features… the ones that made the biggest difference are all about turning off the GPS receiver as much as possible. It will be turned off after a configurable period of time where no movement has been detected, and wake up again when the operating system notifies the app that there’s been a “significant location update”. The OS detects those significant movements by keeping track of which cell tower is in use and which others are visible, so having Ham Tracker sitting quietly in the background waiting for such events consumes very close to zero extra battery. There are also configuration options (in v1.2 which isn’t live yet and is waiting for Apple’s review team to resume work after Xmas) to cause the app to wait for cell changes after each position report when the battery is below a certain level, and to tell it to not do anything at all below another level. The idea is that it should be set and forget, without needing to worry about how much battery is being used.

I mention the methods behind those features because I don’t know how it will cope on a summit where several mobile network cells may be visible. I don’t know whether there will be lots of cell changes in that environment, which would wake up the GPS receiver quite often. In the worst case though, I think it could only cause similar amounts of battery usage to the other APRS apps. If it proves to be a problem on summits then I’ll find a way to work around it, perhaps by preventing a wake-up for a while if there are too many within a short period of time.

I hope this post isn’t considered to be too much of an advert, but I thought the battery saving stuff might be of interest.


Mark / G7LEU

In reply to G7LEU:
What if you have a Blackberry instead?

In reply to G1STQ:

What if you have a Blackberry instead?

Then you need to watch:

Colin G8TMV

In reply to G1STQ:

What if you have a Blackberry instead?

You have the knowledge that I helped in the design and verification of several of the semiconductor components. :wink:


In reply to G7LEU:
The question about being on a summit where several mobile network cells may be visible, or any other location, on top of a city centre office block, where you have good RF takeoff always interests me. What are the reasons for the network coverage usually being so poor in these situations?
The phones usually alternate between full signal strength shown on the display and no coverage.
My thoughts in the past have been that the receiver is being overloaded with so much RF about. That the TX power is reduced right down because of the strong RX signal present, and the cell RX aerials are optimised to tilt downwards and are not looking for signals above them?
Am I in the right area or way off?

Pretty much right. The cell site antennas have (broadly) the same TX and RX patterns. The networks are designed for an optimum C/I (or Ec/Io) ratio that takes into account losses due to clutter. Once you are above the clutter those criteria no longer apply and the phone struggles to make much sense of what it’s hearing. For hilltop phone work I sometimes carry a corner reflector made of cardboard with tinfoil stuck on it. That can really help.



In reply to G3CWI:
Thanks for the reply Richard. A quick search for C/I(Ec/lo), as I had not seen the notation before, threw up a white paper by Andrews CommScope on Smartbeam Antennas, which answered a lot of my questions about base station aerial systems.
Carrier/Interference ratio seems similar to signal/noise ratio.