Not enough range - Page 2 - Electronic Circuits Projects Diagrams Free

Roff · 30th July 2004, 04:56 AM

Well, if that's your idea of tweaking, OK. I was thinking bias voltage and/or current.

zachtheterrible · 30th July 2004, 05:05 AM

So . . . should I put the varicap in my circuit and I'll get this huge range?
Or should I make the circuit that you made, and I'll get the huge range?

I've also got a question . . . How does the varicap work to make this huge power jump?

pike · 30th July 2004, 08:16 AM

without bothering to read the above posts, it is probably your transisitor that has a hfe of 16. When testing make sure it was totally disconnected from the circuit.

If it is not that increase the supply voltage !!! this is the easiest way to boost range. Provided that all the components are rated above the supply voltage it is fine.

zachtheterrible · 1st August 2004, 02:56 AM

Hate to bring back up an old subject, but I got the simulator, and finally figured out how to make it work right, now I got a couple questions about the oscillator that panic mode posted:

1. What is the purpose of having two coils, and connecting to the pwr source in the middle of them?

2. Is this the best performance that can be had w/ a 9 volt battery, and a pretty simple circuit?

3. In SWCAD, is there any way to see frequency?

zachtheterrible · 1st August 2004, 06:40 PM

Got some more questions about this circuit here. I put an audio amplifier on the oscillator that Panicmode made.

Is this a good simple amplifier?

Can I put an antenna between L1 and C2, or does it have to be between L2 and C3, cuz the voltage between L1 and C2 is 49 to -21v, and the voltage between L2 and C3 is 0 to 35 volts.

If the voltage goes negative, like 49 to -21 volts, do I get more power, or is it just like 0 to 49 volts?

Is there any way to improve this circuit without getting real complicated? (like putting in 1 or 2 more components) I want this thing to be small. It has to fit in a tiny project enclosure.

panic mode · 3rd August 2004, 04:19 AM

zach,

Back to original question (bigger range). If you are not sure how to determine oscillator frequency or to tweak it for more output, you might
want to stick to proven designs to avoid frustration. Although circuit I
posted does work, I had to pick values that would work in sim to prove that higher amplitude of the oscillations is possible with minimal change,
so do not use 100uH and 100pF for FM transmitter.
In this case base frequency of the oscillator is only few MHz because
of used LC values.
To get bigger range out of the transmitter you already have, try replacing
transistor in the oscillator for different one or simply make bigger transmitter. Instead of tiny FM oscillator with only few mW of power
you can build one with few Watts of power like this one here:
http://www.mariucci.freeserve.co.uk/fm2w.gif
I've built it only few times and it sure kicks a$s but it tends to drift more
than those little transmitters (at least that was my experience).
About checking what's the frequency in the simulator, you have to run it
to get the charts. Right click on the oscillogram and in the bottom
of the popup menu you will notice FFT (fast fourier transformation).
Zoom at the peak of the FFT diagram to read the frequency. You will
notice other spikes like harmonics...

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30th July 2004, 04:56 AM	(permalink)
Roff	Well, if that's your idea of tweaking, OK. I was thinking bias voltage and/or current.

30th July 2004, 05:05 AM	(permalink)
zachtheterrible	So . . . should I put the varicap in my circuit and I'll get this huge range? Or should I make the circuit that you made, and I'll get the huge range? I've also got a question . . . How does the varicap work to make this huge power jump? __________________ I'm no electronics god, i just talk too much.

30th July 2004, 08:16 AM	(permalink)
pike	without bothering to read the above posts, it is probably your transisitor that has a hfe of 16. When testing make sure it was totally disconnected from the circuit. If it is not that increase the supply voltage !!! this is the easiest way to boost range. Provided that all the components are rated above the supply voltage it is fine. __________________ www.winpicprog.co.uk - Great PIC language tutorials.

1st August 2004, 02:56 AM	(permalink)
zachtheterrible	Hate to bring back up an old subject, but I got the simulator, and finally figured out how to make it work right, now I got a couple questions about the oscillator that panic mode posted: 1. What is the purpose of having two coils, and connecting to the pwr source in the middle of them? 2. Is this the best performance that can be had w/ a 9 volt battery, and a pretty simple circuit? 3. In SWCAD, is there any way to see frequency? __________________ I'm no electronics god, i just talk too much.

3rd August 2004, 04:19 AM	(permalink)
panic mode	zach, Back to original question (bigger range). If you are not sure how to determine oscillator frequency or to tweak it for more output, you might want to stick to proven designs to avoid frustration. Although circuit I posted does work, I had to pick values that would work in sim to prove that higher amplitude of the oscillations is possible with minimal change, so do not use 100uH and 100pF for FM transmitter. In this case base frequency of the oscillator is only few MHz because of used LC values. To get bigger range out of the transmitter you already have, try replacing transistor in the oscillator for different one or simply make bigger transmitter. Instead of tiny FM oscillator with only few mW of power you can build one with few Watts of power like this one here: http://www.mariucci.freeserve.co.uk/fm2w.gif I've built it only few times and it sure kicks a$s but it tends to drift more than those little transmitters (at least that was my experience). About checking what's the frequency in the simulator, you have to run it to get the charts. Right click on the oscillogram and in the bottom of the popup menu you will notice FFT (fast fourier transformation). Zoom at the peak of the FFT diagram to read the frequency. You will notice other spikes like harmonics...