UK cellphones are normally about 6W?, they don't use UHF, they use much higher frequencies - the power output though is switched according to the signal strength from the nearest mast, so would rarely approach the full 6W.
As suggested, cellphones are 'line of sight', so could go a considerable way with fairly low power, however the high frequencies used tend to limit it - which is the whole point of cells.
Using a handheld 2M amateur radio transceiver (1W out) I used to easily get 70 or 80 miles - from the top of a hill! - in the bottom of a valley you get coverage of the valley, and that's about it!.
As suggested, cellphones are 'line of sight', so could go a considerable way with fairly low power, however the high frequencies used tend to limit it - which is the whole point of cells.
Using a handheld 2M amateur radio transceiver (1W out) I used to easily get 70 or 80 miles - from the top of a hill! - in the bottom of a valley you get coverage of the valley, and that's about it!.
I’ve got a 500mW 446Mhz Oregon Two-ways and it only gives out 5km = 3.106856 Mile and it’s heavy on the battery’s
But a cell phone you can talk hours long.
So what’s the secret behind that, and how can I build my own long range line of sight transmitter that uses 100mA to transmit up to Miles and Miles long just like a cell phone does, my main purpose of this device is to build a data link
But a cell phone you can talk hours long.
So what’s the secret behind that, and how can I build my own long range line of sight transmitter that uses 100mA to transmit up to Miles and Miles long just like a cell phone does, my main purpose of this device is to build a data link
jacquesl said:
I explained above - a cellphone uses very low power because it's mostly only transmitting to a nearby mast, and the handwset adjusts it's power output to the minimum required (to extend battery life, and to reduce the possible damage to your brain).
Also, the batteries are MUCH, MUCH better than the ones you're using in your Two-ways - which are also pretty poor things, not like a 'proper' transceiver at all.
Cell phones put the burden of performance on the base station side, sensitive receivers and above all, very high gain antenna arrays with optimized beam coverage.
An answer to your requirements must first start with with knowledge of things like if you want unrestricted portability or you are only interested in a fixed point to point link etc.
Rodolfo
PS And don't even dream of building an amplifier without a fair amount of experience and RF test equipment.
An answer to your requirements must first start with with knowledge of things like if you want unrestricted portability or you are only interested in a fixed point to point link etc.
Rodolfo
PS And don't even dream of building an amplifier without a fair amount of experience and RF test equipment.
RF design is complicated, and layout is critical - particularly at the high frequencies you would need to use. Presumably you want a decent data rate?, a normal radio channel probably manages 1200 baud or 2400 baud?. If low rates are all you need?, you might try googling for "packet radio" - radio hams use a device called a TNC (Terminal Node Controller) which is essentially a modem between a computer and a transceiver.
Another problem is the legality of it - you will almost certainly require a licence, which won't be available for what you want to do!.
Another problem is the legality of it - you will almost certainly require a licence, which won't be available for what you want to do!.
Yea, packet radio will probably be the best option for me now, but I want some scary fast speed over long distances I already checked out the packet radio, but it didn’t tickled me so much, but I’m going to do a monster search on Google now.
The only thing is, how the pc manages it to switch PTT button automatically then you want to TX stuff
The only thing is, how the pc manages it to switch PTT button automatically then you want to TX stuff
jacquesl said:
The faster the speed, the higher the bandwidth, and the lower the range - unless you increase the power to compensate?.
The TNC does it all, most have micro-processors in them, the PC simply sends and receives serial data, the TNC packets it up, and keys the transmitter as required. I've still got one here, I did 2m packet for a number of years - I think it's a Kantronics KPC2 - or something like that?, I haven't seen it for years. I actually wrote my own PC software for it - in Turbo Pascal 5, it was that long ago - pre-Windows.
I went to Bazaruto Island off Mozambique with a cruise ship once.
I had this ancient nokia.. the kind you could use for self defence due to its size.... in the evenings all the ship staff would come to the deck at the rear to see if they could get reception on their fancy phones from overseas... I only lost reception after about 2 days of sailing... everyone else had very dissapointed looks.
I had this ancient nokia.. the kind you could use for self defence due to its size.... in the evenings all the ship staff would come to the deck at the rear to see if they could get reception on their fancy phones from overseas... I only lost reception after about 2 days of sailing... everyone else had very dissapointed looks.
For 1200 baud or 2400 baud, packet radio seems to be slow, it doesn’t make any sense why it’s so slow why not use 2 x 2-ways on each base station and have a dedicated send and receive channel open to operate 2 radios sound better to me. So no more PTT button respond time delay needed, will it increase the speed with a monster amount?
jacquesl said:
There may be licence restrictions preventing it?, it's been so long I can't remember now - also it's not trivial to operate full duplex, you certainly need to be crossband to make it practical.
The PTT isn't a problem due to the packet system, it pressed PTT and sends the packet, then drops the PTT and awaits the reply.
Packet stations can also relay other peoples data, you can reach right across the country through other peoples stations - although it's obviously a slow business!.
The speed is mainly governed by the bandwidth, a voice width channel can only do slow speeds.
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