Hi everyone.
I built a simple amplifier to be used as a transmitter.
There's a transistor oscillator circuit, coupled via a transformer to a class C rf amplifier (30 uH choke at the collector, and 68 ohm resistor from base to ground). That's all.
It is soldered neatly. No protoboard. Working at 7 MHz.
For some reason, transformer's secondary phasing affects the circuit performance (in other words, swapping the secondary leads)
With secondary in phase with primary:
- I get more power.
- The waveforms at the base of the rf amplifier are "noisier".
- The collector voltage shows a second "peak" (this is later filtered by a pi filter, and the output to the load is sinusoidal).
Attached, real measruments of both pashings.
With some transistors, the power difference is small. For others, it is quite large.
Could anyone explain why the secondary phasing (which, by common sense, should not have an impact) changes the base and collector waveforms and usually gets higher outputs?
Thank you very much!
I built a simple amplifier to be used as a transmitter.
There's a transistor oscillator circuit, coupled via a transformer to a class C rf amplifier (30 uH choke at the collector, and 68 ohm resistor from base to ground). That's all.
It is soldered neatly. No protoboard. Working at 7 MHz.
For some reason, transformer's secondary phasing affects the circuit performance (in other words, swapping the secondary leads)
With secondary in phase with primary:
- I get more power.
- The waveforms at the base of the rf amplifier are "noisier".
- The collector voltage shows a second "peak" (this is later filtered by a pi filter, and the output to the load is sinusoidal).
Attached, real measruments of both pashings.
With some transistors, the power difference is small. For others, it is quite large.
Could anyone explain why the secondary phasing (which, by common sense, should not have an impact) changes the base and collector waveforms and usually gets higher outputs?
Thank you very much!
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