Please help - UK Electronics Student

[miles]

Please could you help me. I need a small transmitter (with a range of about 100m), where the signal strength can be differentiated over about 40cm. In other words, I want two receivers to monitor signal strength - one about 40cm behind the other. And they must be sensitive enough to give a stronger signal strength for the receiver closer to the transmitter.<p>I would be very grateful if you give me information about the type of transmitter/ receiver set up I would need and where to get it. Also if you could advise me on how to build a signal strengh indicator circuit, that would be great.<p>I am an english A-level student, and this project is a big one - its important. Thank you for your help.<p>Cheers<p>Miles

[bodgy]

Miles,<p>I thought its the new term so is this for this years 'A' levels or NVQs?<p>Anyhow my brain isn't quite working this morning so I'm not sure I've got your question correctly, BUT, the I think you require something along the lines of a nulling receiver - it's how the TV detector vans work. Now Maplin used to have a kit for one of these circa 1994, you will also find details in the RSGB book - I doubt Smiths will have it, but Maplin used to stock it, and if Waterstones stock is still slightly different from old WH then there selection of technical books used to be better.<p>The signal strength meter - Practical Wireless often have this as a project, again the RSGB book and if you can get it the American equivalent the ARRL. You don't say what type of modulation or the frequency band - I assume to be licence exempt we are talking 418MHz or 27MHz?<p>Bugger - I'll start again now I understand - basically you want two receivers that show received signal strength.
How do you propose to show the signal on a line of leds or using a moving coil meter. If this is a Superhet system then the signal meter could be inserted (with buffering) on the AGC line or at the demodu;ation diode.<p>You still need to specify the frequency and the mode of transmission. A google search will bring up a lot of diagrams for ideas.<p>colin

[miles]

I am half way through my A-Levels - so one more year until uni.<p>Thanks for your help. To be more specific I need the setup as part of a guidance system for an automated product.<p>You are right in that I will require 418Mhz frequency transmitter and recievers. However, the signal strength circuits will not output to a LED or moving coil meter; they will go into a further circuit which will compare the signal strengths - to decide which way it is to turn.<p>This is why it is very important that the signal strength indicator circuits will be able to give a slightly stronger reading for the reciever closest (by about 40cm) to the transmitter (which could be between 3m - 80m away).<p>There will be no data transferred by the radio signal and only one band. As I said it is a form of remote guidance and a comparison of the two signal strengths is the essence of this design. <p>Thanks <p>Miles

[bodgy]

Righty 'O',<p>I assume you are allowed to use 'black box' technology - esp to stay within the regulations, so for your tranmitter/receivers use one of the ready made modules from RF solutions www.rfsolutions.co.uk or www.bitztechnology.com or www.radio-tech.co.uk or www.ratiometrix.co.uk.<p>OK so they do the modules AM or FM. With the FM modules to detect signal strength all you need to do is monitor the RSSI output.<p>Now if you really want to show off there is the new device from Atmel the TRX01 I don't know the cost but there is a development board available AT86RF211 some details were in Elektor June edition.<p>All have data sheets available. Maplin used to sell them but then they seem to have gone a bit seedy recently.<p>Colin<p>PS. Good luck with your 'A' levels - I remember mine well. Strangley the School closed down soon afterwards.<p>[ September 03, 2002: Message edited by: bodgy ]</p>

[miles]

Thank you, that has been very very helpful.<p>Regards<p>Miles