Constant tone on 27.265 LSB

It's either in the radio, which is my guess, or as Dusty said, nearby electronics.
Just out of curiosity here, have you tried hooking a different antenna to it? Have you checked the SWR of the antenna to the radio?
I'd start by putting a meter on it to check the SWR. If that is off, you could be getting a feedback into your receiver. Although that shouldn't happen unless you are actually transmitting. But start your checking with the antenna.
If all else fails, can you lock out the problem frequency on your rig? If you can't, or if doing that is something you can't live with, I guess taking it to a tech is the next step.

 

After listening to this again, I think it could be coming from an outside source.
Does the radio do this everywhere, or just where you happened to be parked?
Is this something that just started?
Is this a new radio?
Or a new installation of a radio you've had for some time?
Is this a radio that has worked well for you in a different vehicle?

 

I used to get loops that picked up engine ECM radiation. From what I see, the antenna is part of an RF loop and it may be due to a ground problem. Note: the tone is absent when antenna is removed. I would look at the pwr supply connection, check for ground loop, a choke may be needed.

https://en.m.wikipedia.org/wiki/Choke_(electronics)

 

If that is the case, what happens when someone strips a microwave and uses it to push 10,000 watts against a big truck at 70 mph hauling hazmat?

 

According to this website:http://www.cbradiosplus.com/mobile/...www.cbradiosplus.com:80/product_p/2970n4.htm=
The radio does have

Of course that could be either a misprint or a mistake.

 

Anyone get a constant annoying noise on channel 11. It sounds like a generator and is present 24/7 whether the truck is on or not. I know channel 11 is the little bowl, so I wonder if some big operator is trying to jam it, but it is also there whn skip isnt rolling

 

What you are talking about....A rail gun!

 

Actually, I get annoying noise on almost every CB channel. It's mostly from the CB Rambo's.....