Apart from the squeel, there's also a high noise floor which is noticable when transmitting with no audio in the form of white noise.
One possible source seems to be the microprocessor as the noise changes in time with the temperature display changing form faranheit to celsius and back. It's also more pronounced when the backlight is lit so as an alternative, this possibly points to noise from the switch mode supply.
There are no known mods at present but a few strategically applied electrolytic caps may help enormously.
We hope to bring you more once a solution has been found.