Oscillator circuit

[zachtheterrible]

Hello all, I've got a couple simple questions about this oscillator here.

Can I put the antenna where the green arrow is pointing? Cuz it's getting a lot more voltage than the blue.

Why have the two coils? Y not just 1?

Any improvements that I could make to this circuit?

Finally, the green voltage is going down to -21 volts, is there any way of making it go down to 0 volts, and therefore get a better amplitude?

Thanx SOO much for your help

 

[Russlk]

L1 and L2 is actually one coil with a tap. The tap makes it an impedance transformer so the Q of the coil is improved, making it more stable. If you did not model it as a transformer, you will not get the expected results. The impedance of a 1/4 wave antenna is about 75 ohms, so it that is what you have, find a tap on the coil that matches 75 ohms. That will be closer to the bottom than the top.

 

[Roff]

Mr. Terrible, I played with that sim for an hour or so, and I couldn't get it to stop squegging ( look that up in your Funk & Wagnall's). If you can't get the oscillator to put out a clean, stable signal, there's no point in trying to modulate it and transmit it. Maybe Panic Mode knows how to clean it up.

 

[panic mode]

This might be just quirk of the software. Try putting same value for both
L1 and L2.

 

[zachtheterrible]

So this isn't a clean signal, even if it's in a pattern?

What is an impedance transformer, and how would I model it on a sim?

Russlk said that I should put my antenna closer to the bottom than the top . . . Isn't the stronger signal @ the top??

I do want 2 try n build this despite what you said about frustration in the other thread panic. I know how to calculate LC n all that n i just finished reading a book on radio (although it didnt teach me enough), so by fiddlin with this Im gaining a lot of knowledge. thanx 4 all the help, without all u helpin me id still b in square 1.

 

[panic mode]

thats the spirit

 

[Russlk]

I simulated just the oscillator, using mutual coupling between L1 and L2. I had to edit the spice file because I don't see any symbol in the Switcher Cad for it. With C3 = 100pF, Q1 was saturating real hard so I reduced C3 to 10pF with better results.

 

[Russlk]

For those interested, I will try to attach the edited Spice file. Hmm, my editing is gone, so I don't know if it ran with mutual coupling or not!

 

[Roff]

To add mutual coupling, add a Spice directive (the ".op" icon) like this:

k1 L1 L2 {k}

Where {k} is your mutual coupling, e.g.,

k1 L1 L2 0.99

Russ, I'm trying to duplicate your results. What node is n004, and what value of k did you use (if any)?

Ron

 

[zachtheterrible]

I would imagine that n004 on russlk's circuit is @ the collector of Q1 . . . my best guess, but y is it @ 2 volts???

I did the mutual coupling between L1 n L2 (thanx btw), and now my circuit is peaking @ 11 volts. In a previous thread, panic mode had the same oscillator peaking @ 44 or so, but the amplitude was very unstable. Is this oscillator an efficient one?

Also, the highest i can get it to go is about 43 MHZ . . . Anyone able 2 get it 2 go higher?

 

[zachtheterrible]

Ya know, I just got thinkin', since this circuit is only going to be putting out 11 volts, i'm going to forget this circuit n move on to bigger n better things. Do any of you know of any transmitters or oscillators along the lines of the one that I posted (2 transistors, minimal components)? I want something small. I was browsing FM transmitters and came across one with a claimed range of 1/2 a mile . . . unfortunately it was one that had to be bought, and therefore no schematic ( :x ). Neway something w/ even a 1/4 mile would be GREEEEEAAT! Thanx!!

 

[Russlk]

Ron: I used k=.90 but don't think it was used, the circuit works the same with no coupling. My simulation ran at 4Mhz. I would use a more standard Colpits or Hartley circuit and a more powerful transistor to get more range. You have to match the output to the antenna to get any range. I bought a 144mhz transmitter and receiver that had 1000 feet range on miliwatts.

 

[Roff]

I would use a more standard Colpits or Hartley circuit and a more powerful transistor to get more range. You have to match the output to the antenna to get any range.

I totally agree.
Or how about the famous hybrid oscillator that is part Armstrong and part Colpitts. I believe it's called the Armpitt oscillator.

 

[zachtheterrible]

Ron, r u sure that its the armpitt oscillator, i searched google n this site n didnt find nething

 

[Roff]

Another term for it is the Axilla oscillator.

Perhaps I should explain that this a poor attempt a humor, in the same vein as the rumor that Fairchild Semiconductor and Honeywell were going to merge. The new company would be called Farewell Honeychild.

Sorry.

 

[zachtheterrible]

AAAAAHHHH HAAA HAAA :lol: . That was perdy funny. heh heh. I thought u were serious, and that it was just a weird name.