I want to build this transmitter: enter image description here

The inductor in the schematic says 0.1uh so I figured I could get some of these and use them instead of making my own like it describes in the picture. I would be using these. Do you think they would work? Any information appreciated.


No don't buy it unless you are prepared for disappointment. There are no details about this at all i.e. it does not appear to have a data sheet so you won't know: -

  • Its natural resonant frequency
  • Its Q factor

Without knowledge of these your oscillator may not work at all or it may not tune to where you want it to. You need to oeprate it substantially below its natural resonant frequency so that it actually behaves as an inductor. Above its resonant frequency it behaves like a capacitor.

If the Q factor isn't big enough it won't oscillate and many inductors using ferrite will become significantly "resistive" or "lossy" above a few MHz. You need your to operate at 100MHz so look for an inductor with a SRF above 1GHz and a Q factor that is at least 20 at 100MHz.

You are looking for an air-core inductor and not one wound on ferrite. The one you linked appears to me to be wound on a ferrite former although I could be wrong on this: -

enter image description here

  • \$\begingroup\$ +1 Based on the markings it looks more like 100uH 10% anyway. \$\endgroup\$ – Spehro Pefhany Apr 3 '15 at 14:55
  • \$\begingroup\$ Thanks for the info...by the way could you explain what the 4.7pf cap does right by the inductor: could I use a 5pf? \$\endgroup\$ – NULL Apr 3 '15 at 15:05
  • \$\begingroup\$ The emitter is used as an input because it has positive amplification - the capacitor feeds back a little to the input to keep oscillations sustained i.e. it's positive feedback. \$\endgroup\$ – Andy aka Apr 3 '15 at 15:39

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.