Yes, it's the right way to do it. The placement of C3 and C2 does the trick, the circuit is considering the critical branches.This is a Veroboard optimized oscillator.
This is a Veroboard optimized oscillator. It is insensitive to parasitic inductances as the RF path around Q1 consists of only four elements. C1 and C2 can each be mounted next to the transistor. The parasitic inductance of C3 10nF doesn´t matter as the coil is in series with it. The oscillator has very high margin: It starts with 2,5V and for the Q-factor of the coil a minimum of 10 is sufficient.
---------- Post added at 10:21 ---------- Previous post was at 10:20 ----------
https://obrazki.elektroda.pl/76_1289033392.jpg
Looking sharp at the new circuit bottomside, there's no feedback connected to the emitter node. It can't oscillate.
The RF feedback to emitter seems correct (look at the picture below).
Zeller, certainly, your connections should be shorter but even though it is still possible to have high frequency oscillations on a veroboard. Once I made a simple FM transmitter and it worked fine at 100Mhz.
Strait capacitances and inductances will decrease the final oscillation frequency. I assume that your board is just a prototype.
Now you have 500 ohms at the emitter and 10Kohms at collector. By using 500 ohms at the emitter, your emitter current in DC should be around 8mA (I assume you are still using a resistor divider at the base using the same values for both resistors).
If Zeller really does want to make an idiotproof 27MHz oscillator on veroboard (it might not be Zellerproof) then build the circuit by bluetooth in post #41.
With 8mA emitter current, the dynamic resistance of the BE junction is estimated to r(be) = 25/8 = 3 Ohms.
This BE junction resistor is practically in parallel with the 331pF capacitor (C3) - rf equivalent transistor circuit in small signal - At 27MHz, the 331pF represents about 18 ohms and the 3ohm BE junction resistor is acting like a shortcut to ground. I guess this is the main reason why it is not oscillating.
You should ALWAYS have r(be) bigger than the impendance of C3, for example something like 100 should be nice. But a good compromise it to have 1mA at emitter in DC, so I would suggest to replace the 500 Ohm at the emitter by one of 4K (once again).
This SHOULD WORK FINE!! because now you have a 10K at the collector.
KEEP TRYING, we are all with you
Your post doesn't help. The board you are showing is for the awful circuit posted in post #29.
But you weren't looking at the same board. The comments about missing feedback weren't aimed at the original vero PCB. Like I said your comment was of no use.The board I was showing in my last post was referring to a previous post where it was said that there was no feedback connection to emitter. I only wanted to confirm that the feedback connections were OK.
Please, build the post #29 circuit yourself and put a 10k ohm resistor in the collector and see what happens to the DC voltage at the collector. Forget about making an oscillator, this circuit becomes a saturated DC switch.As you can expect, I do not agree with your statement. My point of view is just different from yours. You are suggesting a new-like design for a Colpitts oscillator while I am trying to understand why the last Zeller's circuit is still not working without suggesting a new design.
Do you agree with me now? Your (I say not useful) 10k + 500R circuit suggestions made an already poor design into a DC switch instead of an oscillatorAs you can expect, I do not agree with your statement.
You did some maths to calculate the emitter current so what do you think will happen to the DC voltage at the collector if you try and pull about 8mA through 10k ohm at the collector?
(You can't ever get 8mA emitter current if you put 10k in the collector anyway)
...and now I would like to see whether my circuit (post #41) is zellerprooved. Its minimum partcount, simulated with ansoft and microcap and contains 30 years oscillator building experience...
Zeller, please try.
Bluetooth,Congratulations! I see on your picture a 555 timer circuit. Do you want to modulate a square wave tone? For this you don´t need a timer. You can change the values in the oscilator circuit and it generates some khz AM and the 27MHz simultaneously.
I need to know what receiver do you want to use! Is it a CB receiver or a shortwave AM radio? Is it a SSB radio? Is it a wideband superregenerativ receicer? This is important as the frequency stability must match the receivers bandwith.
Can clarify, which final circuit you're referring to, and how did you probe it, also what's the probe impedance?
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