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RF help needed please

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Nelliecat

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Hi, I am a new member to this forum and it has been 15 years since i last worked with a PCB at uni!!

I am in the process of designing / inventing a piece of kit and require help and advice combining various bits of electronic knowledge.

Simply, what would i need to transmit simple information such as temp, a switch position (on / off) to a base unit (which would be mains fed or rechargeable battery) over a distance over less than 1 mile (2 at most). There would also need to be a sound transmission as well.

There would need to be about four parameters, and hopefully distinguish different sets of sensors (no more than 4).

I have had a play with simple "walkie talkies" and it would seem this would be the cheapest / smplest route to go down with a few modifications. Also had a play with a simple RC car.

Any initial help to point me in the right direction would be appreciated.

PKH :shock:
 
Nelliecat said:
Hi, I am a new member to this forum and it has been 15 years since i last worked with a PCB at uni!!

I am in the process of designing / inventing a piece of kit and require help and advice combining various bits of electronic knowledge.

Simply, what would i need to transmit simple information such as temp, a switch position (on / off) to a base unit (which would be mains fed or rechargeable battery) over a distance over less than 1 mile (2 at most). There would also need to be a sound transmission as well.

There would need to be about four parameters, and hopefully distinguish different sets of sensors (no more than 4).

I have had a play with simple "walkie talkies" and it would seem this would be the cheapest / smplest route to go down with a few modifications. Also had a play with a simple RC car.

Any initial help to point me in the right direction would be appreciated.

Your first move should be to enter your location in your profile! - then we might know where in the world you might be!.

This is particularly important for your request, as you need to investigate the legal aspects first.

Most countries have short range licence free frequencies available (which varies from country to country), and you can buy ready built modules at reasonable cost. As far as I'm aware you're not allowed to build your own from scratch?, if you did you would presumably have to submit them for testing and approval (an expensive undertaking) - again, this probably varies from country to country.

As for more legal aspects, walkie talkies are almost certainly NOT allowed to be used for this purpose, the band is only licenced for voice transmissions. Likewise the radio control bands probably don't allow this eitther?, you essentially want to send computer data over a radio link!.

The licence free system, as I mentioned, are short range - I don't know if you can get them that would work far enough - but check the suppliers and regulations for the country you live in.

You also need to check the regulations concerning voice transmissions, most don't allow both!.
 
Get your daughter to marry the engineer at a local FM station.
They can transmit just about anything on a subcarrier. :lol:
 
Thanks for prompt reply Nigel, will update my profile!

Actually up in Baxenden (home of Holland Pies!!) so not a million miles away. Thanks for the info - very useful.

I was thinking about the baby monitor type of arrangement, where voice (one way) is carried along with limited data (temp etc). These seem to use 40Mhz range, although range is limited to say 100m. I would need a similar setup but over say 1-2 mile, even one mile would do. the voice would only need to be one way as well.

Hopefully could use free license but we will see.

Thanks for your help, do you know where i would go to have a prototype circuit built. I know what i need plan wise, but have no idea how to translate into a circuit diagram(s). I presume their are companies who will be able to take a rough map / description of the perceived function and turn it into a reality?

PKH
 
Hi Russ,
I'm in Canada, not far from you.
Cell phones here hardly ever work properly, maybe because most are American! :lol:
 
I've never been in Riski's lap. Where did you meet her? Alberta?
 
Nelliecat said:
Actually up in Baxenden (home of Holland Pies!!) so not a million miles away. Thanks for the info - very useful.

Sorry, but I've never heard of Baxenden, or Holland's Pies - it's mostly Pukka Pies round here :lol:

I did a quick google, and see you're near Accrington - I've heard of that!.

As you're in the UK, I don't think there's any legal way you can do what you want - it MIGHT be possible to get a radio licence for it?, BUT this is difficult to do, EXPENSIVE (£100's per year!), and the equipment isn't cheap.
 
Several comments:

Depending on your purpose for the transmissions you might be able to fit that under an amateur radio license which could be low cost but allow you to use all sorts of modes. If UK is like the US then amateur license only covers hobby and experimental which might also include personal research (as long as the research is legal!!).

Can you actually see the receiver from the transmitter? Would a laser work?

Just some thoughts. Good luck.
 
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