Its been forever since making a good FM transmitter but I couldn't figure it out unless LTSpice is garbage software, I don't know. I don't own an oscilloscope and maybe now I need one in the worst way, however I want to avoid that as it costs big money.
Anyways, If I strip the extensions from this circuit starting at wire n002 (aka the class-e amplifier), I could pull off a basic transmitter by making fine adjustments to R2 and R1 and C6 (under R1), but the problem is, the transmission range is rather too weak. I'll be lucky to pull off 50 feet. I'm looking for one that can transmit at least 200-400 feet.
I'm trying to transmit at about 433Mhz. I believe C5, C2, and L1 make a colpitts oscillator that determines this frequency. I'm willing to change the values of C5 and C2 later on if necessary.
capacitor C1 (located under n002 label) is tricky. I was told somewhere it represents part of a high-pass filter, but if I use a higher value I feel more signal can go through yet at the same time, it causes the overall transmission frequency to change. can someone verify this? I also tried connecting C1 to emitter without success.
I used a 1m resistor as an attempt to feed part of the input to the final stage but that made things worse.
I need to fix this so I can transmit at least 200 feet, however there are restrictions since I am adding this to another project with microcontrollers:
1. The source voltage coming into the transmitter is 5VDC which is fed through a 7805 voltage regulator. This regulator currently shares its output with everything else (including the microcontrollers).
2. The input signal (when transmitter is 100% done) is a fixed 32Khz square wave with output coming from the output pin of a 74HC86 XOR gate. (that will be connected to IN and the 20Khz signal will be removed). However, I want to test this thing first, so the input will be audio (between 0 and 20Khz) from my computer at normal volume.
3. The antenna will be a 6-inch shielded 22awg wire with about 1 inch stripped from the end.
4. I need to use the fewest tuning elements possible (preferably 1, the capacitor across the inductor would be the only thing I'd like to tune).
and of course...
5. I must not break any law. which means if I have to select a different frequency, then I will.
So what can I do to fix this?
and if the simple answer is to increase voltage, would 5VDC sourcing a charge-pump circuit (made of diodes and capacitors) be sufficient to power this circuit and produce long range?
Anyways, If I strip the extensions from this circuit starting at wire n002 (aka the class-e amplifier), I could pull off a basic transmitter by making fine adjustments to R2 and R1 and C6 (under R1), but the problem is, the transmission range is rather too weak. I'll be lucky to pull off 50 feet. I'm looking for one that can transmit at least 200-400 feet.
I'm trying to transmit at about 433Mhz. I believe C5, C2, and L1 make a colpitts oscillator that determines this frequency. I'm willing to change the values of C5 and C2 later on if necessary.
capacitor C1 (located under n002 label) is tricky. I was told somewhere it represents part of a high-pass filter, but if I use a higher value I feel more signal can go through yet at the same time, it causes the overall transmission frequency to change. can someone verify this? I also tried connecting C1 to emitter without success.
I used a 1m resistor as an attempt to feed part of the input to the final stage but that made things worse.
I need to fix this so I can transmit at least 200 feet, however there are restrictions since I am adding this to another project with microcontrollers:
1. The source voltage coming into the transmitter is 5VDC which is fed through a 7805 voltage regulator. This regulator currently shares its output with everything else (including the microcontrollers).
2. The input signal (when transmitter is 100% done) is a fixed 32Khz square wave with output coming from the output pin of a 74HC86 XOR gate. (that will be connected to IN and the 20Khz signal will be removed). However, I want to test this thing first, so the input will be audio (between 0 and 20Khz) from my computer at normal volume.
3. The antenna will be a 6-inch shielded 22awg wire with about 1 inch stripped from the end.
4. I need to use the fewest tuning elements possible (preferably 1, the capacitor across the inductor would be the only thing I'd like to tune).
and of course...
5. I must not break any law. which means if I have to select a different frequency, then I will.
So what can I do to fix this?
and if the simple answer is to increase voltage, would 5VDC sourcing a charge-pump circuit (made of diodes and capacitors) be sufficient to power this circuit and produce long range?