HELP: I am building an Pixie 2

[sm5mek]

And i have a strange motorboat sound from the receiver,  LF is LM386, anyone having tips to filtering this? 

[PG4I]

Hi Jenny,

make sure your power supply decoupling is okay. Where the supply is connected to the LM386 add a 100uF electrolytic capacitor in parallel with 100nF ceramic. Connect them as close to the LM386 as possible. Also, make sure your grounding leads are as short as possible.

[WH7TT]

Trying using a battery as well to see if the sound is still there. That will tell you if it is the Power Supply or something else.
Edward
WH7TT

[sm5mek]

Trying using a battery as well to see if the sound is still there. That will tell you if it is the Power Supply or something else.
Edward
WH7TT

Well i shifted the battery and the putt putt was dissapearing. NICE. Before that i also found a tiny tiny shortcut :-) but the motorboat was still rhere, could be that the shortcut was taking so much current so the IC didnt get enough current. Now weak hissing like a lazy cat. More tests in future.

[n7eku]

Hi Jenny,

My first post here :-)

Almost every design I see using the lm386 forgets that pin 7 should be bypassed to ground.  Any small value electrolytic should be fine (5-20uF) and helps a lot.

Have fun with your pixie!

73,


Mark/n7eku

[sm5mek]

I now got the motorboat away and heard my own signals very loud (hi) it was several problems, bad and cold solder as one, putting some component to correct point also good to do.    so now have a check about the shift between tx and rx, a buisness about values to the capacitor and trimmer at the x-tal.

[AK0B]

low battery voltage will also make the audio sound like its bubbling
stan ak0b