I think there's a PLL to do the band selection like the TS120 and 130. It could be loosing lock from low voltage. My dad's TS 440 spreads out when its supply voltage gets low. That back scatter underwater sound isn't from a bad tube. Its from a bad oscillator. 73, Jerry, K0CQ -- Entire content copyright Dr. Gerald N. Johnson, electrical engineer. Reproduction by permission only.