Why this simple Tx catches the noise from any device like TV, PC, transformers...?

[Willen]

It is Harry Lythall's bug 5 and I did little modification and this Tx has been produced.

It catches noises of AC transformers (used on any devices) far from almost 10 meter. It's working very nice but if I turned on the TV or PC or Cell phone charger etc then Tx starts to transmit noise. I am using Battery but the noise says "you are using AC to DC adapter" hahaha

OF COURSE I used 1nF and 10uF De-coupler capacitor at supply to filter low and high noises however...

Other simpler Tx is not catching such noise but why only on this Tx? (as C2 I used 220pf and L2 might be higher than 500nH little)

Are there any foolish connection by me?

 

[Rotarymaker]

It is Harry Lythall's bug 5 and I did little modification and this Tx has been produced.

It catches noises of AC transformers (used on any devices) far from almost 10 meter. It's working very nice but if I turned on the TV or PC or Cell phone charger etc then Tx starts to transmit noise. I am using Battery but the noise says "you are using AC to DC adapter" hahaha

OF COURSE I used 1nF and 10uF De-coupler capacitor at supply to filter low and high noises however...

Other simpler Tx is not catching such noise but why only on this Tx? (as C2 I used 220pf and L2 might be higher than 500nH little)

Are there any foolish connection by me?

Hi Willen,

Have you fitted Cx = 22uf decoupling capacitor as shown as instability mod on Harrys site?

http://www.sm0vpo.com/tx/bug5.htm

Otherwise if this doesn't fix problem, double check your pcb / layout / connections.

regards,
Rotarymaker

 

[Willen]

I used 10uF and 1nF decoupling capacitor instead of 22uF at supply.

 

[Rotarymaker]

I used 10uF and 1nF decoupling capacitor instead of 22uF at supply.

Hi Willen,
Please try a 22uF.....it will need to be mounted close on your circuit board as shown on Harrys website, as I listed for you above.
He quotes this necessary mod from his website .....

There used to be a 1n0 5mm cap for supply decoupling, but after a cange of component supplier (manufacturer?) there developed some form of RF instability when the gain of the PA transistor was a little above normal. Replacing the 1n0 to an electrolytic capacitor of 22uf cured this problem totally

If this doesn't work, can you tell us what way your circuit layout is?.....is it the same as shown website.....same pcb? .... or did you redesign it on vero board / breadboard?
.... it maybe that layout is your problem, rather than circuit decoupling ..... just a thought .... I'm not criticising your work.
regards,
Rotarymaker

 

[Willen]

OK I will use 22uF with 1 nF both (thinking that 1nF is a best filter for 100MHz and 22uF is for LF noise). PCB design is totally like Harry's (I used his design).

I used an inductor instead of 330R at buffer. I used 330pf RF coupling capacitor instead of 1nF.

I will feel great even if you criticised my design or work.