tinytrak, does it really work?

marsjell · 08-03-2002, 02:53 AM

Hi all,

I've been playing with the thought of using a tinytrak for LO-jacking puposes. I finally decided to order the PIC and start building. When I contacted the dude who sells them in holland he asked me what my CALL was so he could programm it into the pic. I responded telling him that I had no idea what a CALL was, and explained what I wanted to use the tinytrak for.
His reply was that it couldn't be done, something 'bout the frequency range of a GSM not being broath enough for ax25 protocol, so that some tones will not be "heard" or misinterpreted.

opinions anyone?

Dimitris1976 · 08-03-2002, 04:50 AM

That person thought you are a licenced Amateur Radio Operator and wanted to know your "Callsign" in order to intergrate it in Tinytrack's firmware. That way every time you transmit your coordinates over the VHF/UHF amateur bands your callsign (station identification number) will be aired too according to the rules. This of course is not necessary since your are going to use it with a cell phone and not with a radio transmitter.
As for the sound quality and audio frequency spectrum of the GSM phone network being not sufficient for this application I have to say that this person propably didn't know and he just tried to find something "smart" to say to you. GSM is all digital and has crystal clear audio as long as you have the minimal signal strength or no audio at all (if the reception is not good in the area). On the other hand amateur radios that are used along Tinytrack usually have worst audio quality.
Bottom line it works. I works for me, for a few friends of mine that I built units for them and for many people that contacted me over e-mail asking "how to" questions .

marsjell · 08-03-2002, 05:29 AM

where did you order your pic? seems this dude won't sell it to me because he thinks it won't work

aprsmobiel · 08-03-2002, 06:49 PM

Hi,

Iam the 'DUDE' from Netherlands who do not want to sell to Marcel.
Marcel,
tell not the full story about why not sell him
but thats his problem.

First iam 60++ years of age and being for 35 years a techical engineer.
We tested this in the year 1999/2000.
And its NOT working proper or not at all on normal GSM VOICE CODEC.
Its works okee on GSM DATA channels.
Thats why GSM use voice and seperate data channels on the GSM network to send faxes and other data like video.
So thats a complete other story.

FIRST:
Iam very curious how you pars the tinytrack 1200baud audio data true the GSM VOICE CODEC without loss or get corrupted data?

SECOND:
Do you know how GSM actualy is working?

THIRD:
Way you think GSM is using data channels to use for sending faxes and other data using audio tones?

This i told Marcel aswell.
He, not being a engineer, did not understand this.

73's
Bert

marsjell · 08-04-2002, 06:27 AM

Hi Bertus,

I did understand why I shouldn't work, to set the record straight I AM an engineer I've been an electrotechnic engineer for 4 years and for the past 2 years a software engineer, ok I am an ing. not an ir. and have allmost zero experience compared to your 35 years, but still I am an engineer.

I have no trouble believing you, I understand the point you're making, but seeing that people on this board DO have it working I wanted to try it too, as I said, I'm pretty hard-headed.

best regards,

Marcel

aprsmobiel · 08-04-2002, 09:06 AM

Just let Demetri explane how he done this.
Thats all i like to know.

BTW,
there are botes engineers, planes engineers,
software engineers and many other kind of engineers.
All those fine people making lovely thinks on there own speciality and branche

Myself being a radio development engineer and retired.
I worked with GSM, and other cordless equipment to develop all kind of products for companys or use it myself.

Just do a simple test like this:
- Take a audio tone generator.
- and a simple scope.

Connect the audio tone generator to the MIC input
of the GSM phone.

Connect the scope to loudspeaker wires from your normall house-phone.
(like normal telephone modem)

Tone generator send oud tones from 500Hz, 1000Hz,
1500Hz, 2000Hz 500Hz steps up to 3500Hz true the mic input of the GSM phone.
Same time view the scope on the other (cordless) end of the telephone line.

Just let me know what you see on the scoop on fallowing items :
- view tone on the mic input before go into the GSM mic input.
- and view speaker output of the house-phone when passed the GSM CODEC and phoneline cable.

Iam very pleased to here your conclusions!

Or second test, turn the test units around.

Connect tone gerator to microfoon wires of your house-phone.
And scope to the speaker wires from your GSM.

Again,
just let me know what you see on the scope view
this time.
This simple test give very good idea how GSM CODEC is actually working.

When you have GSM alignment tools/equipment.
Just view the 'jitter' and 'echo' on the GSM VOICE CODEC line.
Again,
GSM VOICE CODEC is totaly differ from GSM DATA line who used for DATA like faxes = audio tones.

Both VOICE and/or DATA uses different ways inside the GSM protocol and data channels.

Have fun.

Bert.

Dimitris1976 · 08-05-2002, 09:19 AM

I am not an engineer, I don't know how GSM protocol works but I do have an osciloscope and a medical grade audiometric tone generator and I understood exactly why this thing shouldn't work. According to you (and I don't have any reason not to believe you), GSM voice protocol for bandwidth saving reasons has only the necessary frequency range (around the frequency the average human larynx generates) in order to support a decent telephone quality conversation, while it filters out lower and higher frequencies since it's a phone and not a Hi-Fi after all.
On the other hand I know for sure that it is working 'cause it's working right now in front of my eyes.
I'll conduct my own tests as soon as I find some spare time.
By the way I am using my phone for WAP and I sent faxes through it using my PDA. There is a option in my phone that I activated before I do that, that says "fax and data". Is there any chance that this made any difference?
On the other hand I don't know what my friend's phone settings are and it's working for them too.