QRP Club

QRP Station => Builder's Corner => Topic started by: sm5mek on March 26, 2015, 09:57:01 UTC

Title: HELP: I am building an Pixie 2
Post by: sm5mek on March 26, 2015, 09:57:01 UTC
And i have a strange motorboat sound from the receiver,  LF is LM386, anyone having tips to filtering this?  :-\
Title: Re: HELP. I am building an Pixie 2
Post by: PG4I on April 01, 2015, 06:50:11 UTC
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.
Title: Re: HELP. I am building an Pixie 2
Post by: WH7TT on April 01, 2015, 17:17:06 UTC
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
Title: Re: HELP. I am building an Pixie 2
Post by: sm5mek on April 08, 2015, 07:35:31 UTC
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.
Title: Re: HELP. I am building an Pixie 2
Post by: n7eku on April 26, 2015, 23:52:25 UTC
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
Title: Re: HELP. I am building an Pixie 2
Post by: sm5mek on April 28, 2015, 07:36:42 UTC
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. :-\ ^-^
Title: Re: HELP: I am building an Pixie 2
Post by: AK0B on October 04, 2015, 03:04:01 UTC
low battery voltage will also make the audio sound like its bubbling
stan ak0b