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Anonymous
 
Posted on Tuesday, May 31, 2005 - 3:17 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

I built both the computer controlled transmitter and the AM transmitter. The latter works over a distance of about six inches, and the former works when the transmitting and receiving antennae are touching. How can I make the broadcast signals stronger? I have an excellent ground, and an 18-inch antenna from an RC car.
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Simon Quellen Field (Sfield)
Senior Member
Username: Sfield

Post Number: 463
Registered: 12-2004
Posted on Tuesday, May 31, 2005 - 3:44 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Did you read the section in the Radio chapter about antennas?

You will have a little trouble getting a nice quarter wave resonant
dipole antenna for 1 Mhz, but get as close as you can.

The speed of light is 299,792,458 meters per second.
Our frequency is 1,000,000 cycles per second.
Thus one wavelength is 299.792458 meters.
A quarter wave dipole would thus be 75 meters long.

18 inches will not radiate well, and most of the energy will be reflected
back to the oscillator, and merely heat up the final output transistor.
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Anonymous
 
Posted on Tuesday, May 31, 2005 - 4:16 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

Thanks for the quick response!

When you say 75 metres, does the antenna have to reach that far out, or is the number just how long the wire is? In other words, can I coil/fold the wire and get similar results?

Also, and this is just me throwing things out into the air, it seems to me that the computer controlled transmitter can be used for more than morse code without making any adjustments. Is this true, or am I mistaken?
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Simon Quellen Field (Sfield)
Senior Member
Username: Sfield

Post Number: 464
Registered: 12-2004
Posted on Tuesday, May 31, 2005 - 4:47 pm:   Edit PostDelete PostView Post/Check IPPrint Post   Move Post (Moderator/Admin Only)Ban Poster IP (Moderator/Admin only)

You would have to fold it properly.
You can fold it improperly in such a way that one part
undoes what another part is doing. There are lots of good
books on antenna design.

Yes, you are not limited to Morse Code. Try TCP/IP.

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