MW AM Transmitter with BandStop notch Filter

Hi I have built this MW transmitter

http://www.naturemagics.com/ham-radi...itter.shtmfrom base to emitter

but I notice that it has a problem when ever I touch any of the audio parts as well as RF it tends to change frequency or go into some sort of oscillation, I have been powering this from a portable CD player even touching that causes problems. I have come up with the Idea of using a brand-stop filter where the Audio goes in from base to emitter, I was wondering if this is a good Idea or bad. would using a brand pass at the end of aerial be a good idea as well.

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do have a look where I put the filter, I used some online calculator to get the values.

I don't think that this is primarly a problem of RF leakage to the audio input. In so far, I don't expect much effect of the filter. The problem is rather caused by detuning the oscillator through capacitive loading of either the signal ground or antenna node. A more promising way to get rid of it would be to change the circuit to a two stage oscillator and output amplifier design, or to stabilize the single stage oscillator's frequency by a crystal.

As FvM and interpose another audio amplifier stage so the mic is not connected directly to the oscillating transistor. Your layout is totally RF screened?, is it not?
Frank

Where is your Vcc bypass cap? (A value like .1 uF or .047 uF at these freqs.)

A cap that should be placed between +V and -V that provides elimination of the RF voltage that will otherwise be present?

Without bypass cap an additional 'feedback' circuit also exists in the circuit.

In many circuit, it sometimes is *assumed* that bypass caps are present, or the power supply provides adequate bypass at the working frequency, however, in the real world, 'bypassing' of some sort is required, and it does not hurt to have too much bypassing.

Jim