I was thinking I might like to try building a part 15 AM transmitter. I DO understand it would not be reasonable to expect Rangemaster-like performance, but I was wondering where I might find some schematics for some good circuits for 520-1700kHz operation?
I tried temporarily building one using a science fair radio shack kit, but it drifted HORRIBLY (even taking into account the variable capacitor to tune it), and it had NO range - signal faded out completely on a walkman after about 20 feet, even with a few foot antenna wire strung up. Also, the audio quality was awful - badly distorted, and NO treble response. No, I wasn't expecting much range out of it (based on past experiences), but I was expecting SOMEWHAT better frequency stability and audio quality.
Where (I've tried Google, but don't know what to search for) would I look for some schematics of decent part 15 AM systems?
Also, to keep the frequency locked on, would it be easier to use a fixed-value capacitor, a crystal, or a PLL synthesizer?
I would probably be temporarily constructing it on a Radio Shack 300-in-one breadboard science fair kit, then if it works ok, would transfer it to a better package.
Also, assuming I get it set up properly (and legally), how far should I expect my various field strength contours to go? I'm at approx 32°46'N 116°57"W. I've been following the thread someone posted on this forum asking about field strength measurements for part 15 am stations with interest, and am STILL waiting for someone to respond with actual data.
Also, I understand that operation IS permitted above 1705kHz, but with a specific field strength limit (you can't use the 100mW 3meter rule). ( http://a257.g.akamaitech.net/7/257/...ccess.gpo.gov/cfr_2004/octqtr/47cfr15.209.htm http://a257.g.akamaitech.net/7/257/...ccess.gpo.gov/cfr_2004/octqtr/47cfr15.223.htm )
Taking those limitations into account, is it possible to have a good quality signal within about 50 to 100 feet of the transmitter? I would expect full quiteting of the background noise or better - for example, signal strength of the part-15-compliant transmitter at 1730kHz (my SRF-42 will tune up to 1750) at 50 feet would be the same as that of a typical 50kW AM station within 2 miles of their transmitter.
I tried temporarily building one using a science fair radio shack kit, but it drifted HORRIBLY (even taking into account the variable capacitor to tune it), and it had NO range - signal faded out completely on a walkman after about 20 feet, even with a few foot antenna wire strung up. Also, the audio quality was awful - badly distorted, and NO treble response. No, I wasn't expecting much range out of it (based on past experiences), but I was expecting SOMEWHAT better frequency stability and audio quality.
Where (I've tried Google, but don't know what to search for) would I look for some schematics of decent part 15 AM systems?
Also, to keep the frequency locked on, would it be easier to use a fixed-value capacitor, a crystal, or a PLL synthesizer?
I would probably be temporarily constructing it on a Radio Shack 300-in-one breadboard science fair kit, then if it works ok, would transfer it to a better package.
Also, assuming I get it set up properly (and legally), how far should I expect my various field strength contours to go? I'm at approx 32°46'N 116°57"W. I've been following the thread someone posted on this forum asking about field strength measurements for part 15 am stations with interest, and am STILL waiting for someone to respond with actual data.
Also, I understand that operation IS permitted above 1705kHz, but with a specific field strength limit (you can't use the 100mW 3meter rule). ( http://a257.g.akamaitech.net/7/257/...ccess.gpo.gov/cfr_2004/octqtr/47cfr15.209.htm http://a257.g.akamaitech.net/7/257/...ccess.gpo.gov/cfr_2004/octqtr/47cfr15.223.htm )
Taking those limitations into account, is it possible to have a good quality signal within about 50 to 100 feet of the transmitter? I would expect full quiteting of the background noise or better - for example, signal strength of the part-15-compliant transmitter at 1730kHz (my SRF-42 will tune up to 1750) at 50 feet would be the same as that of a typical 50kW AM station within 2 miles of their transmitter.