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brian
Unregistered guest
Posted on Sunday, April 24, 2005 - 1:11 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

hi i am planning on building the transmitter , the one that works with your pc. i was planning on using it to communicate with my friend a few miles (2-3 miles) down the road and was wondering if your model had the range, and if not how to achieve this range.
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Simon Quellen Field (sfield)
Senior Member
Username: sfield

Post Number: 323
Registered: 12-2004
Posted on Sunday, April 24, 2005 - 4:13 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

If you have an Amateur Radio license and a good receiver,
an oscillator at 28.8 Mhz into a good antenna will go
around the world.
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MadScientist (madscientist)
Junior Member
Username: madscientist

Post Number: 10
Registered: 4-2005
Posted on Sunday, April 24, 2005 - 11:15 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Hell, If you have the right antenna, a linear is not all that far fetched, and is legal in some locations, that would more than do this... Sorry Simon, Im a science fanatic (not saying youre not hehe) and this just happens to be right up my alley.. I bought a transmitter module recently, albeit FM, that is capable of 1/4 mile right out of the box... tweak it and its capable of well over a mile. In the process of learning what I could and couldnt do, I found a site, that is mostly devoted to what youre thinking. http://www.part15.us has massive amounts of information that will tell you what you can and cant do in the AM band... Some of the transmitters built are legally transmitting more than 5 miles... just keep an eye out, the FCC doesnt play around. Your range will depend on what frequency you plan to operate at, as well as how much power you will use and how long your antenna is... The ones described on this site are very low power and would require boosting that potentially puts them outside the legal range. Do your homework first! Having the FCC and their associated droids banging on your door cant be a good thing, I have heard stories of as much as $10,000 per transmission, PER OFFENSE! It is wise to make sure youre not interfering with anything before you do something like this!

Steve
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Simon Quellen Field (sfield)
Senior Member
Username: sfield

Post Number: 331
Registered: 12-2004
Posted on Monday, April 25, 2005 - 10:38 am:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Don't use a linear amplifier with the AM transmitter I designed for
the web page. My design was optimized for simplicity, and has no
filtering on the output to prevent spurious emissions on harmonic
frequencies. An AM transmitter that can legally transmit 5 miles
under the U.S. Part 15 regulations would need good filtering.

I have been having fun building radio transmitters for the last 40
years (I hold an Amateur Extra class license). But if everyone
started jamming the amateur bands with splatter from amplified
unfiltered oscillators, my hobby would lose a lot of its appeal. ;-)
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MadScientist (madscientist)
Member
Username: madscientist

Post Number: 20
Registered: 4-2005
Posted on Tuesday, April 26, 2005 - 9:06 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

That was pretty much my point, I didnt mean to strike a nerve hehe, I was thinking more along the lines of the simple 2 transistor designs than anything even approaching, say, a 1000W module (or anything even remotely approaching). I was thinking more along the lines of 100mW. Granted, even the device as I was contemplating could definitely cause problems (Im assuming that the output from the osc module is square), and would cause unacceptable harmonics. I was essentially ranting, throwing ideas around... :-) On that note, I stand corrected, and no, it would not be acceptable to run anything like this for any length of time, but would prove the concept.

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