mstechca
New Member
Your quest isn't over :lol: (or maybe it is)
Anyways, I'm happy to inform some of you that the varactor trick has partially worked with my receiver.
Here's why:
The resistors I used for each bit from the 4-bit counter are as follows:
1.2K
2.7K
4.7K
6.8K
I deliberately went over 1K for each value and tried to exponentially increase each resistor value based on what remaining resistance values I had on hand.
When I used my computer (I wrote a Qbasic program) to calculate all possible resistances based on each counter state, I was happy to see that the voltage increments were small enough (about 6%) if the counter went through each bit combination in order.
So that I believe is not too much of a percent. My supply voltage is switchable between 6 and 9V because I want to make my circuit work with a 9V battery for as long as possible. (please don't tell me to buy duracell or energizer, or some other premium brand battery)
Audioguru made a transmitter circuit showing a diode and capacitor in series. I made it so that it appeared compatible with my receiver.
Here were the results I got when I tried these values for diodes and the coupling capacitor:
test #1
Diode: 1N4007
Capacitor: 150pF
Additional capacitance added: None
Result: No signal
test #2
Diode: 1N914B
Capacitor: 150pF
Additional capacitance added: None
Result: No signal
test #3
Diode: 1N914B
Capacitor: 22pF
Additional capacitance added: None
Result: No signal
test #4
Diode: 1N914B
Capacitor: 22pF
Additional capacitance added: 4.7pF
Result: Signal present only on two values (not bits).
It makes me think that a diode can only produce a small capacitance.
When I tested my circuit with just a standard LC circuit (no varicap add-on), and when C is 4.7pF, I got white noise in, which is good for now.
I also added a 50% voltage divider. (two 680K resistors), because if I had all high bits or all low bits, I can't see how the circuit would work without them. The center of the divider as well as the output voltage from my counter is connected to the center of the varicap circuit. (between the reverse biased diode and capacitor).
I begin to think that changing the diode to one compatible with higher frequencies might do the trick. What do you think?
My objective is to get any signal in when I press the button. When I press it again, I want the signal (or at least the frequency) to change.
Anyways, I'm happy to inform some of you that the varactor trick has partially worked with my receiver.
Here's why:
The resistors I used for each bit from the 4-bit counter are as follows:
1.2K
2.7K
4.7K
6.8K
I deliberately went over 1K for each value and tried to exponentially increase each resistor value based on what remaining resistance values I had on hand.
When I used my computer (I wrote a Qbasic program) to calculate all possible resistances based on each counter state, I was happy to see that the voltage increments were small enough (about 6%) if the counter went through each bit combination in order.
So that I believe is not too much of a percent. My supply voltage is switchable between 6 and 9V because I want to make my circuit work with a 9V battery for as long as possible. (please don't tell me to buy duracell or energizer, or some other premium brand battery)
Audioguru made a transmitter circuit showing a diode and capacitor in series. I made it so that it appeared compatible with my receiver.
Here were the results I got when I tried these values for diodes and the coupling capacitor:
test #1
Diode: 1N4007
Capacitor: 150pF
Additional capacitance added: None
Result: No signal
test #2
Diode: 1N914B
Capacitor: 150pF
Additional capacitance added: None
Result: No signal
test #3
Diode: 1N914B
Capacitor: 22pF
Additional capacitance added: None
Result: No signal
test #4
Diode: 1N914B
Capacitor: 22pF
Additional capacitance added: 4.7pF
Result: Signal present only on two values (not bits).
It makes me think that a diode can only produce a small capacitance.
When I tested my circuit with just a standard LC circuit (no varicap add-on), and when C is 4.7pF, I got white noise in, which is good for now.
I also added a 50% voltage divider. (two 680K resistors), because if I had all high bits or all low bits, I can't see how the circuit would work without them. The center of the divider as well as the output voltage from my counter is connected to the center of the varicap circuit. (between the reverse biased diode and capacitor).
I begin to think that changing the diode to one compatible with higher frequencies might do the trick. What do you think?
My objective is to get any signal in when I press the button. When I press it again, I want the signal (or at least the frequency) to change.