Continue to Site

Welcome to our site!

Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

  • Welcome to our site! Electro Tech is an online community (with over 170,000 members) who enjoy talking about and building electronic circuits, projects and gadgets. To participate you need to register. Registration is free. Click here to register now.

Inductor question

Status
Not open for further replies.

zachtheterrible

Active Member
Will having a wire practically touching an inductor in a parralel LC circuit in an FM transmitter cause frequency drift? The wire that I am talking about is the positive of my power supply.
 
If the wire is parallel to the axis of the inductor it could pick up some of the field of the inductor, causing FM noise on your supply line which in turn may upset the circuit. This effect would be less if the wire crosses at right angles, though I still would place decoupling capacitors on this line close by.
Klaus
 
forgive my thickheadedness but I don't know what you mean by deecoupling capacitors. Around what value should they be?

also, if I have the capacitor in the LC circuit directly by the inductor (as in the coils are touching the plastic of the cap) could this cause frequency drift?
 
:)
The frequency drift is caused by variations in L or C parameters of your circuit, including parasitics. These variations can be induced by temperature variations especially for C, you must use a C with low temperature coeficient such a polyester cap. The ceramic cap for example have a high temperature coeficient and a lot of temperature drift. Other cause for drift can be L drift which can be produced by variations in magnetic field geometry especially in case of air inductors which no have magnetic core, in this case any conductor or magnetic object put close to inductor can modify the magnetic geometry and the value of L. But if positions of these objects are fixed the real frequency of oscilation can be diferent by your expected but no drift.
 
Well then what is causing the frequency drift!?!?!?!?!?!?!?!?!? It's definately not temperature, and it's definately not anything disrupting the magnetic field cause everything that is a conductor is constant. What's happening is that it will be crystal clear, drift a little bit, and then I won't be able to get any signal at all. AAAAAAAHHHHHHH :evil: :twisted: :x This is driving me insanse!!!!
 
zachtheterrible said:
Well then what is causing the frequency drift!?!?!?!?!?!?!?!?!? It's definately not temperature, and it's definately not anything disrupting the magnetic field cause everything that is a conductor is constant. What's happening is that it will be crystal clear, drift a little bit, and then I won't be able to get any signal at all. AAAAAAAHHHHHHH :evil: :twisted: :x This is driving me insanse!!!!

A free running VHF oscillator is very likely to have drift problems, that's one reason they are difficult to build. Layout at VHF frequencies is pretty crucial, I suggest you try rebuilding it in a different way - but remember, keep every thing as short and neat as possible!.

If you want to eliminate drifting you need to build a far less crude design, preferably using a crystal oscillator and multiplier stages.
 
Status
Not open for further replies.

Latest threads

New Articles From Microcontroller Tips

Back
Top