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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.
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.
Without parasitics it will oscillate at 27,2MHz. If you decouple power via an 1pF cap at the collector you will get 27,0 MHz. With 10pf from collector to output you get 25,5MHz. If you connect a 10pf cap from the emitter to output jack you get 27,0MHz. If you dont use 50 Ohm load the frequencies...
...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.
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...
@Zeller,
I alsused Microcap and simulated and it oscillates in Microcap. But: If I add a series resistor of 0,03 Ohm or more in series with the 429nH inductor it will not work. In real life you have about 4 Ohm in series with your smd-inductor. This resistor gives you the real Q-factor of the...
Your oscillator coil has probably a Q-factor of only 20 if it is SMD type in 0603 or 0805 package. So simulate with such a low Q-inductor with 470nH (Z= j76 Ohm @ 27MHz) and add a series resistor with 4 Ohm in your simulation. You get better Q-facor with more inductance and bigger size. I would...
Did you measure P-DC when measuring P1dB? Is P-DC constant or raises your drain current by probably two times or three times when you raise your input RF power? I don´t know know what derivative superposition is. Can you please explain?
Thanks.
Re: IP3 measurement
@jameslee: The IMD3 is 2*f1 -f2. Probably you apply the harmonic of f1 direct in the lna?. Did you use an lpf to cut off the harmonic off your signal source generator?
P1dB is measured at output and not at input? P1dB - at output measured - should be proportional to P-DC. If this is not the case your mosfet goes into voltage saturation or current saturation and not both simultaneously. This is due to output mismatch.
For 100MHz don´t use microstrip resonator. It will be much to big. Built a colpitts LC Oscillator with about 150nH...220nH Resonator inductor and appropriate capacitors. If low close in phase noise is important use RF Feedback and big emitter resistors of about 2,2kOhm for small collector current.
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