Radio Orienteering - Page 2 - Electronic Circuits Projects Diagrams Free

stevez · 18th October 2007, 08:19 PM

Yes, reflection is possible though at 80 meters I'd think it less of an issue up close.

forever99482 · 12th November 2007, 03:10 PM

If I wanted to install a PIC/AVR into the circuit, at which stage should I actually do it? (as in after bandpass filtering? or put a differential amp after the antenna then feed it to the PIC?)

**Nigel Goodwin** · 12th November 2007, 03:44 PM

You don't use PIC's in RF circuits!.

RadioRon · 12th November 2007, 06:50 PM

Quote:

Originally Posted by forever99482

Thanks, will look up on it now

Actually, I was wondering if it is possible to build an antenna which the shape look like the antenna of the old type mobile phone (those that you'd need to pull out the antenna type)? because the loop type antenna is sort of bulky and not really user friendly. (In terms of having to point in the right direction to get a maximum signal)

Actually, this is my 3rd year project, trying to beat other teams XD

No, if you make an antenna that is a straight wire it will not be directive at all. This is mainly because your frequency, around 3.5 MHz, is quite low and the wavelength at this frequency is approximately 80 meters long. Any straight conductor antenna that is much shorter than a quarter wavelength will have no directivity at all. The only way to get some directivity out of something like this is to build an array of them and use some sort of phase indicating receiver to show direction of arrival for the wavefront. This is complicated. The loop is a lot simpler, and will actually work. A straight wire such as you ask about will not.

RadioRon · 12th November 2007, 06:57 PM

Quote:

Originally Posted by forever99482

If I wanted to install a PIC/AVR into the circuit, at which stage should I actually do it? (as in after bandpass filtering? or put a differential amp after the antenna then feed it to the PIC?)

Why would you want to stuff a processor into something that doesn't need it? Sounds like you are trying to create a "software defined receiver" by replacing the receiver analog circuits with a PIC/AVR, which is a needless overcomplication.

forever99482 · 12th November 2007, 07:11 PM

As I need to connect a GPS(sorry if I forgot to mention it earlier) to it and store the logged data, I'd probably need a PIC or something right?

**Nigel Goodwin** · 12th November 2007, 09:48 PM

Quote:

Originally Posted by forever99482

As I need to connect a GPS(sorry if I forgot to mention it earlier) to it and store the logged data, I'd probably need a PIC or something right?

Yes, but it's not connected to the RF side.

forever99482 · 12th November 2007, 10:18 PM

So right after the antenna, there would be one wire going into a differential amplifier, and one going into the RF amp?

TekNoir · 17th November 2007, 05:01 PM

Do you need to record data from the RF transmitters or just the GPS?

If only the GPS, I would recommend building a separate (even if you put it inside the same housing) NMEA 0183 data logger for connection to the GPS. You should be able to use any 8-bit or better MCU for this. Your favorite search engine will give more details.

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18th October 2007, 08:19 PM	(permalink)
stevez	Yes, reflection is possible though at 80 meters I'd think it less of an issue up close. __________________ stevez

12th November 2007, 03:10 PM	(permalink)
forever99482	If I wanted to install a PIC/AVR into the circuit, at which stage should I actually do it? (as in after bandpass filtering? or put a differential amp after the antenna then feed it to the PIC?)

12th November 2007, 03:44 PM	(permalink)
Nigel Goodwin	You don't use PIC's in RF circuits!. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

12th November 2007, 07:11 PM	(permalink)
forever99482	As I need to connect a GPS(sorry if I forgot to mention it earlier) to it and store the logged data, I'd probably need a PIC or something right?

12th November 2007, 10:18 PM	(permalink)
forever99482	So right after the antenna, there would be one wire going into a differential amplifier, and one going into the RF amp?

17th November 2007, 05:01 PM	(permalink)
TekNoir	Do you need to record data from the RF transmitters or just the GPS? If only the GPS, I would recommend building a separate (even if you put it inside the same housing) NMEA 0183 data logger for connection to the GPS. You should be able to use any 8-bit or better MCU for this. Your favorite search engine will give more details.