fred wrote:

You've lost me there. Why would my computer be using a USB3 port for blue tooth?

If you have a USB3 hard drive connected to a USB3
port, at the same time the computer is using Bluetooth,
there can be emissions from the USB3 bits. The emissions
happen to peak at 2.5GHz, the BT is at 2.4GHz.

You can run an external BT dongle off a USB2 port.
That's where mine is plugged in, an add-on to a desktop computer.
Because the BT Nano style is so "stubby", it helps to put
it on an extension cable, to improve line-of-sight operation.

computer

USB3 USB2
| |
| cable BT Nano TX
| \
USB3 .
hard \
drive BT_Headphone

In such a case, the RF emissions coming from the
left of the diagram, can upset the low power signal
from the BT on the right.

The USB3 emissions, spectrally, look like this.
A broad peak at 2.5GHz, that can smother 2.4GHz
communications device. This is a "data-related"
emissions pattern, not a "clock spike". A clock
spike, if the technology allowed it, would be about
20dB higher than this broad data-related leakage
pattern. Normally, data-related leakage is far
enough down, it might not require remediation to
correct it (meets FCC Part 15).

Level |
| --
| -- --
| -- --
+----------------- Frequency GHz
0 2.5 5.0

Intel has a white paper about this.

https://www.intel.com/content/www/us...nce-paper.html

It's not guaranteed that every active USB3 device
emits RF like that. But, the Intel paper serves
as a warning that manufacturers should do quality
verification work and not release junk to the market.
Usually, you rent time at a third-party facility for
testing. At work, we had a $4 million lab with all
the necessary equipment, for verifying stuff out
to 20GHz or 40GHz or so. And that facility was
pretty solidly booked for testing. It was anechoic
and for near field work. We had a separate facility
for far field verification, which wasn't nearly as
fancy. It was some distance from a company soccer field :-)

If a person having a BT problem, has the hardware
configuration in the top picture, they should
unplug the USB3 hard drive, then retest their BT operation.

Paul