In reply to HB9BIN_3:
A battery’s effective capacity can drop to 10% in extreme winter conditions. (You may have noticed it starting your car!) Operating discharges it thus the terminal voltage drops especially under loaded conditions. No wonder if the built in regulators of the RIG cannot handle the extreme voltage swings perfectly and the tone becomes somewhat (?) chirpy.
But who cares it? A somewhat chirpy tone is a must in the final stage of an activation as it were waste of energy taking home even a single electron left in your battery! This is the bouquet of SOTA! And what is more, an activator’s (often weak but) chirpy tone distinguishes itself in the QRM of chasers!
Unfortunately I missed you. Maybe next time I can QSO you!
73: Jóska, HA5CW