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Electronics => Electronics => Topic started by: Admin on July 02, 2009, 01:50:01 PM

Title: looking for wireless transceiver under 50MHz
Post by: Admin on July 02, 2009, 01:50:01 PM
I'm looking for a wireless transceiver that must be under 50MHz and give at least 1kbps. Off-the-shelf is best, I don't want to make anything if I have a choice.

Anyone have experience converting a cheap 27MHz toy remote/receiver to transmit TTL data?
Title: Re: looking for wireless transceiver under 50MHz
Post by: airman00 on July 02, 2009, 02:44:11 PM
Quote from: Admin on July 02, 2009, 01:50:01 PM
Anyone have experience converting a cheap 27MHz toy remote/receiver to transmit TTL data?
Nope, but I have used cheap walkie talkies for data transfer. Just output DTMF tones and decode them.
Title: Re: looking for wireless transceiver under 50MHz
Post by: Admin on July 02, 2009, 02:49:02 PM
Quote from: airman00 on July 02, 2009, 02:44:11 PM
Nope, but I have used cheap walkie talkies for data transfer. Just output DTMF tones and decode them.
Old school! Got part #'s and schematic? Know the baud rate?
Title: Re: looking for wireless transceiver under 50MHz
Post by: airman00 on July 02, 2009, 02:58:58 PM
Quote from: Admin on July 02, 2009, 02:49:02 PM
Quote from: airman00 on July 02, 2009, 02:44:11 PM
Nope, but I have used cheap walkie talkies for data transfer. Just output DTMF tones and decode them.
Old school! Got part #'s and schematic? Know the baud rate?
from my memory:
Used the Mitel 8870 DTMF encoder, bought it from BA Micro or something similar to that, maybe BA Electro?
Schematic was found in the datasheet, baud rate not sure. I guess it would be limited by the minimum tone length - I think I used the a tone length of 50mS , but I'm sure you can do shorter than that. The datasheet should have info about that. Also, only 16 tones available so you communicate sort of in "hex"
Title: Re: looking for wireless transceiver under 50MHz
Post by: sonictj on July 02, 2009, 03:01:41 PM
Quote
BA Micro or something similar to that, maybe BA Electro?

BG micro maybe? http://www.bgmicro.com/ (http://www.bgmicro.com/)
Title: Re: looking for wireless transceiver under 50MHz
Post by: airman00 on July 02, 2009, 03:03:12 PM
Quote from: sonictj on July 02, 2009, 03:01:41 PM
Quote
BA Micro or something similar to that, maybe BA Electro?
BG micro maybe? http://www.bgmicro.com/ (http://www.bgmicro.com/)
Yep, good catch!
Title: Re: looking for wireless transceiver under 50MHz
Post by: Admin on July 02, 2009, 03:42:35 PM
Quote
The datasheet should have info about that. Also, only 16 tones available so you communicate sort of in "hex"
Any reason for not using just two tones for binary?

50ms for a single bit is waaaay slow. If I can't find any better solutions, I might read into the datasheet to see how fast it can really go . . .
Title: Re: looking for wireless transceiver under 50MHz
Post by: madchimp on July 02, 2009, 05:01:35 PM
I may be way off but wouldn't transmitting in "hex" 16 tones allow you to transmit 4 bits a shot rather than just a single bit as in binary? so the first tone would represent 0000 the second 0001 the third 0010 and so on?
Title: Re: looking for wireless transceiver under 50MHz
Post by: GearMotion on July 02, 2009, 07:14:30 PM
Quote from: madchimp on July 02, 2009, 05:01:35 PM
I may be way off but wouldn't transmitting in "hex" 16 tones allow you to transmit 4 bits a shot rather than just a single bit as in binary? so the first tone would represent 0000 the second 0001 the third 0010 and so on?

I've done things similar to that. The receiver detect chip will have a specification for valid signal detection. Detection of valid dual-tone was about 10ms. Since a dual-tone represents a nibble, then you get about 200 bytes in a second. Not fast enough for admin.