Sidebar Sidebar
  • You can now help support WorldwideDX when you shop on Amazon at no additional cost to you! Simply follow this Shop on Amazon link first and a portion of any purchase is sent to WorldwideDX to help with site costs.

Cobra 148 mk v fm audio tx so quiet

Mrwoosh

Mrwoosh

New Member
Apr 25, 2018
1
0
1
45
Hi all ,

I’ve got a mk v cobra jentec , had it on earlier tx audio was fine on all modes , all of a sudden I was told my audio had almost dropped out on fm ,checked and it had halved in loudness , am and ssb is fine it’s just fm , surly it can’t be the mic as it’s ok on all other modes apart from fm ,

I have got audio on fm but it’s a third to what I had

Any help appreciated

Cheers
 

I don't think I have any technical data on hand for that radio. If I did I would direct your attention to the location of the trimmer pot that sets your FM-transmit audio level.

The trimmer pot that sets your FM modulation level is usually placed near the radio's PLL section.

A customary way the factory will dampen the vibration of parts in the radio's PLL section is by dribbling beeswax over the components in that section. Looks whacky, but it serves a purpose. The voltage-controlled oscillator at the heart of the radio's channel selector is vibration sensitive and can turn into an accidental microphone unless the parts in that circuit are immobilized. Without the wax, the radio's speaker could vibrate those parts and cause an accoustic-feedback howl. If the wax gets onto the FM modulation-set trimmerpot, it can degrade the contact between the trimpot's wiper contact and the resistor element in the trimpot. It usually kills the FM transmit audio completely.

Best educated guess, anyway.

73
 
IT's that older display counter - wow - great stuff.

But that rear RF coil gave away the "date" of that board, just not sure of the type - a 10, 11 or 13 - but no matter how it's sliced. The deviation pot - should be VR5 but that is under that display freq counter...

Man! I'm really old when I start seeing stuff like that and recognize it...

Hey, I had fun -

Regards!
:+> Andy <+:
 

dxChat
Help Users
  • No one is chatting at the moment.


      Top Bottom
      Back