Cobra 139XLR output low on SSB

[Adamf]

Hi all, I have a Cobra 139XLR and AM has good output (5W+) but SSB only peaks at around 7 watts. I adjusted CT7 but that was max, what else can I try please?

Thanks for any help.

Adam

 

[DoctorAudio]

On some of the 858 SSB chassis, the ALC circuit has too much gain and CT7 doesn't have enough range to null the feedback for full SSB power.
Try lifting one end of C155 (1pf disc) and see if you have full power. If so, that is what is happening. To remedy this, put C155 back then change C154 to a 22pf to 47pf. This will give CT7 more range. The higher the value the higher the power output range.

 

[Adamf]

Hey DoctorAudio, can I just say WOW! I lifted C155 as you mentioned and now a little over 22W on SSB. It's good poeple like you that help out the less knowledgeable and I for one appreciate it greatly! I will follow the rest of your instructions to finish the job and thanks again! Adam

 

[DoctorAudio]

I usually change C154 to a value that I'm able to get 14-16 watts PEP. That gives the radio a reasonable output while still limiting. The SSB on that chassis has very good sound and the fast attack characteristics of the ALC circuit makes the limiting action virtually inaudible on the receiving end.

 

[Adamf]

Thanks, I used a 47pf and get about 20 watts out but I don't use the radio that much, just wanted it to work properly. You have been AWESOME. Adam