View Full Version : making something useful from mobile phone
I always wonderd why phones cant talk to each other directly without base stations new ones without antena diplexer could do that easily and save about 90% of money. because power is enough for 3-5 km
does anubody made an attemt to add such functionality?
for that I would need very complete documentation of some cheap mobile phone like sagem mc922 so that i could write new flash. nokia is well docunented but chipset dont have any documentation.
Hi,
This is not technically possible. Reasons:
1. Weak transmitter
2. Not effective antenna
3. Mobile uses Spread spectrum
Even with the best programming you will reach a coverage less
than the cheapest 27 Mhz walkie-talkie.
BR
garfieldpan
10-02-2003, 13:27
to say it simply, based on the formula: c=f*A(can't type such symbol, just use "A" instead, basically it is just the length of the antena) so A=f/c , c is constant, u can't change this, u can only change A and f, but REMEMBER if u change the f(frequency) to be too high it will cause the EMI problem, which will damage YOU and other equipments... so... wot do u think?
you both are wrong.
Transmiter is not weak it is 2-3 W what is huge pover in comparison to walkie-talkie.
Antena is not so bad as you think. or else phone wont work at all.
Modulation type is not a problem i dont mind to use digital modulation too. (and mobiles dont use spread spectrun they use timeslots)
If you dont believe me then check some datasheets.
I am not going to change frequency that much to make antena mismatch. And all that stuff about damage is nonsense.
I already have some work done unfortunately I dont have full shematis of philips diga, which i use, but transmitter and receiver works ok, except i cant use modem and processor because dont know how they are connected.
kingbode
10-07-2003, 14:24
@genuis Digix...
you are totaly wrong and doesnot know any term about what you mentioned.....
you dont need base stations!!!
you want to save money!!!
there is nothing without cost...
and about modulation ( time slots or spreading by code for all usres as in CDMA )
even if ...you need to manage power levels of mobile signals
to elimnate interference..and enhance call resources...
try to achieve what you dream..and you will here noisy call and hear your friends talking too.and bla bla...
what did u study to say that dream!!!!
u may talk about about powe mangement ...
hownto increse users by developing non ordinary code...etc..not kill the base and catch the mobile work station and live with ...!!1
And what is so hard about power management?
Actualy I dont understand waht you want to say ...
For those who dont undersatnd purpose of this project:
broken mobile phone pcb cost 2$ for me, it already have everythig needed to make such super walkie-talkie. I can just take PA make my own design, but it will have much worse performance and high interference. So that is why I want to use other parts too.
Seems there is no way to get all required information now I will probabaly cut processor part of and use microchip pic for that.
Originally posted by Digix
Transmiter is not weak it is 2-3 W what is huge pover in comparison to walkie-talkie.
Hi,
Yes with 2-3 W on 27 Mhz you can cover 100 km and more. On
900 Mhz in a town with internal antenna - 100 m.
Its nothing wrong with the project, the idea to skip the base
station is not good.
BR
I think most problem with up and downchannel freq. separation. mobile phone not designed to receive and tramsmit in same frequency range as walkie-talkie radio.
BETTER WAY: if you fell youself SMART - construct your own base station! :)
2Bph: why 100m ? Mobile-to-base range can be kilometers long.
Originally posted by SFlood
2Bph: why 100m ? Mobile-to-base range can be kilometers long.
Some analog cordless phones on 900 Mhz band can have a
10-15 km coverage by using a very effective antenna at the
base station, high power of the base transmitter ( > 5W) and
installing the antenna at a very high spot in town with as short
as possible cable (very good quality cable).
But the way this high frequency is spread is closer to the light
than the radio waves - it requires a line of sight, and the concrete
is enemy no 1.
Thats why cellular network is using a lot of base stations, at a
high places and having a powerfull transmitters, very effective
array of antennas and very good quality receivers to receive an
weak signal comming from a mobile in some basement or elevator.
Even if you code the mobile to act as a walkie talkie, you can
have a usage only in the country side, not a mountain area , but
land field.
The way two-way radios ( expencive Motorola, Alinco) work is by
using a very powerfull transmitter with narrow as possible band,
good power supply, good external antenna with active
tunning cuircuit controled by the MCU ( to have equal tunning on
all bands/frequencies) and very good receiver for sure ( designed
to receive a weak signals and to adjust its parameters to the type
of the modulation used).
GSM handsets are designed to work as slaves of a Base station.
BR
ktgohdt125
10-31-2003, 18:11
Bph&co can u guide me to enhance cordless phone (electronicly)
& Digix...i like ur idea of modifying hp as a walkie-talkie... let me know how to modify my sagem mc922 handphone...
best regards
aeldarin
11-09-2003, 08:18
I had a similiar idea a while ago, but haven't really researched it thoroughly yet.
I was thinking of modified cellulars as basestations with external antennas attached - preferrably on top of roofs. Or if some SDK and hw-kit for lab use exists (other than the usual US$ 100,000+ boxes), which could provide a cheap basestation.
The basestation would be linked to a PC for gatewaying the voice data over the internet using an elaborate VOIP-plan.
My background is in H.323 VOIP,videconferencing (and some H.324) and SIP - although GSM6.10 is something I've used in earlier projects; including numering plans, Delta3/Iconnecthere.com-type-projects, CISCO VOIP platforms, PABX-VOIP etc.
Of course it would include hijacking some frequencies alotted to GSM-licensees .. but, what-the-heck ... :-)
Basically the idea is using old GSM cellulars with new SIM-cards searching for and connecting to this "rouge service-provider" - like with wi-fi hotspots.
The reason for all this is of course that I see the GSM phones as brilliant technical platforms, but the networked services basically are unimaginative, and lack any proof of living progress. The rampant evolution in P2P, grid computing/data grids, Instant Messaging and others totally pales the lackluster GSM official commercial arena.
Then there's also the lack of any cheapo providers who can use VOIP as a cheaper service, so that the ridicolous international call pricing could be lowered. All of this is of course in part politically caused; remember the ridicolous UMTS-license auctions a few years back ?
The telecoms are some of the worst/biggest debsters in the world - if not truly the #1 companies owning a lot of debth. The cutbacks in BT, France Telecom/Orange among others doesn't seem too promising. Therefore a little user-instigated incentives could rock the boat a little.
Does this sounds feasible with correct antennae setup, PC-software (for basestation decrypting, A3/A8, transcoding [decoding GSM - encoding in e.g. Truespeech (tm)] etc) and SIM-card hacking ?
I haven't got the full oversight yet, but am still researching exploits and software available.
(I actually worked at Nokia Telecom R&D in Finland some years ago, but not in the GSM firmware section; other multimedia networking - in the same building. Should have kept that old sourcecode ;-)
Originally posted by Bph&co
Hi,
Yes with 2-3 W on 27 Mhz you can cover 100 km and more.
BR
Cover the world on 1 watt ;)
Paulsta(G3PEM)
ktgohdt125
11-14-2003, 20:30
is there any new progress yet?
Hi all,
I'd like to discuss some very basics of radio communication, why I had this idea too, and why it (still) seems plausible to me.
1. In ideal conditions, range of a base station is approx. 32 km.
2. This is 2 way communication->if a base station can reach my GSM, I must be able to reach it as well.
3. I'm always in contact with more than base station.
4. Minimal distance that I've seen on any coverage map is way bigger than 100 m.
The biggest problem in situation where only 2 phones communicate with each other are obstacles: buildings, hills etc.
Can anyone tell me what's the range of a mobile phone on a field?
Greets,
Midian
Seems there is some interst afterall,
The interesting part that there is no need to do into gsm frequency,
since we should use unlicensed band which is between gsm tx ant rx.
all gsm voice coding is already implemented in hardware.
But unfortunately it is not possible to do,
I have no way to get full shematic and part specifications (for each one)
for any mobile phone, the most I can find is RF part shematic.
So, no way to make custom firmware for any phone which could simply replace old.(if someone could find such information for any phone it could become profitable buisnes flashing such firmware which converts your phone into some toy for agent 007)
all what I can do is use RF part, and seem there is more easy way,
I decided to use power amplifier from mobile phone and put it into usual 900mhz cordeless phone, that is easy and will have even higer range, because digital modulation is more affected by noise than simple FM.
since such phone with 20mW works in 200m range with (good antena), with 3W power about 5-10km can be expected.
This upgrade should be very easy and probabaly can be done be anyone who have at least little knowledge.
Anyway I was surprised about how low knowlegde some people have here in RF antena and wave propagation principles, if they say that 3w is low power, or if on 27mhz it can cover 100km. everything depend on many factors, and cant be stated so easily, you can reach Moon by using 10 ghz, and 1 km of forest will stop you.
Anyway I was surprised about how low knowlegde some people have here in RF antena and wave propagation principles, if they say that 3w is low power, or if on 27mhz it can cover 100km. everything depend on many factors, and cant be stated so easily, you can reach Moon by using 10 ghz, and 1 km of forest will stop you.
Well like it or not, whatever you tweak in the 3310 software - you can only make
a crap amateur invention out of very good designed and working GSM phone.
For your type of project better start from scratch and use better band(350 - 500 Mhz)
BR