It seems that the last stage in my transmitter controls the transmission distance.
My last stage is the same as the last stage (after the 10pF coupling cap) in the following circuit:
EXCEPT:
for my first transmission attempt:
330 ohm resistor is replaced with a 2.2uH inductor.
150K resistor is replaced with a 36K resistor.
the NPN is replaced with a PN3563 NPN.
It turns out that I get a clean signal for the first street block. As soon as I enter the second block, the signal fades in and out. When I make it to the third block, the signal is mostly faded out.
for my second transmission attempt:
330 ohm resistor is replaced with a 2.2uH inductor.
150K resistor is replaced with a 36K resistor.
the NPN is replaced with a PN3563 NPN.
and I replaced the short between NPN emitter and ground with a 220 ohm resistor, and I connected a 220uF capacitor across that resistor.
It turns out that I get a clean signal for 1/2 the first street block. As soon as I finish the first street block, the signal is mostly gone.
The problem with the first attempt is that the NPN is warm to the touch. It isn't super hot, just warm. The problem with the second attempt is that the range is heavily reduced.
If I did the math, it seems that the resistor connected to the base in both scenarios is not high enough to inject too much current. (333 uA is nowhere near 50mA which is the maximum current for my NPN).
I think the best solution for me is to replace the 220 ohm with a ridiculously low value resistor. Although, I could use heat sinks and deal with the warmth.
What do you guys think?
My last stage is the same as the last stage (after the 10pF coupling cap) in the following circuit:
EXCEPT:
for my first transmission attempt:
330 ohm resistor is replaced with a 2.2uH inductor.
150K resistor is replaced with a 36K resistor.
the NPN is replaced with a PN3563 NPN.
It turns out that I get a clean signal for the first street block. As soon as I enter the second block, the signal fades in and out. When I make it to the third block, the signal is mostly faded out.
for my second transmission attempt:
330 ohm resistor is replaced with a 2.2uH inductor.
150K resistor is replaced with a 36K resistor.
the NPN is replaced with a PN3563 NPN.
and I replaced the short between NPN emitter and ground with a 220 ohm resistor, and I connected a 220uF capacitor across that resistor.
It turns out that I get a clean signal for 1/2 the first street block. As soon as I finish the first street block, the signal is mostly gone.
The problem with the first attempt is that the NPN is warm to the touch. It isn't super hot, just warm. The problem with the second attempt is that the range is heavily reduced.
If I did the math, it seems that the resistor connected to the base in both scenarios is not high enough to inject too much current. (333 uA is nowhere near 50mA which is the maximum current for my NPN).
I think the best solution for me is to replace the 220 ohm with a ridiculously low value resistor. Although, I could use heat sinks and deal with the warmth.
What do you guys think?