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I'm trying to make a tone transmitter that can transmit a tone at least one hundred feet in clear sight to any standard radio on a frequency where no one is broadcasting. I understand that the values in my tank circuit are a bit off, but once I am able to transmit to a radio, then I want to adjust the transmitting frequency.

I tried the first circuit. The enable connection point (of course marked enable) works perfectly, but the transmitting distance seems weak.

I'm thinking of doing the second circuit, but I don't want to waste a circuit board only to find out that it doesn't work.

So using only BJT (NPN or PNP) transistors for the RF portion, how should I arrange the parts for maximum transmission power without violating law? I think my limit is 1/4 watt, I'm not sure.

For initial tests, I'll use 9 VDC but in the end I'll use 5 VDC that's generated from a 7805 regulator that the 9V will feed into.

Should I go with the second circuit or would it function better if I changed how the parts are connected?

Circuit 1:

circuit 1

Circuit 2:

Circuit 2

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  • \$\begingroup\$ If the first circuit produced a working (but weak) result, the second circuit will produce a weak result as well. The radio-frequency part of the 1st is pretty much identical to the 2nd. Be aware that "NOT_ENABLE" in the 2nd is logically equivalent to "ENABLE" in the first. \$\endgroup\$ – glen_geek Sep 18 '16 at 1:54
  • \$\begingroup\$ What physically constituted your antenna and what was your receiver? \$\endgroup\$ – Andy aka Sep 18 '16 at 9:58
  • \$\begingroup\$ My receiver is a homemade transistor superregen. and my transmitter antenna is a 5 inch wire with only 1cm exposed at the end. I think my answer now lies within the value of the feedback capacitor. I'm gonna buy myself some more trim caps and see if I can get more successful. \$\endgroup\$ – user116345 Sep 18 '16 at 17:26

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