Issue

RF gain is to cut out all the background noise and interference. The bars you see is a measure of the strength of the signal in Db. No bars means no signal is being received, so if this happens when he turns up his rf gain its working just fine, unless I am misreading your post. Does he turn the gain knob counter or clockwise?

 

Is he turning the right knob? If so, he might have a bad antenna connection (but receiving you that far, I doubt it). Squelch knob can also do it, depending on where he has it set.

 

No two set-up's will be exactly the same regardless of equipment...

 

The squelch knob would play a part in this scenario. Going indoors could cause the antenna to be picking up electrical interference also.

 

Also the fact this happens with multiple cb's would suggest its either the antenna or coax problem. Or, that there is nothing wrong at all and this is simple paranoia.

 

Did the same person set up all three radios? If he can here 25 miles doubt there is a problem. All the radios I'm familiar with have a meter adjustment inside.