[Elecraft] K3 Keying Up For A Split Second When Power ButtonIs Pushed

[Tom W8JI]

<<<
It took me a copy of tries to make my point to get Wayne to 
make the change,
but at V3.10 of the firmware, he made the following addition 
feature
available:

CW VOX OFF BY DEFAULT ON POWER-UP: Some stations using PC 
control may
inadvertently key the K3 in CW mode on power-up if VOX CW is 
in effect. If
this is an issue at your station, locate the CONFIG:CW WGHT 
menu entry and
tap '4', changing VOX NOR to AUTO  OFF. This will make CW 
VOX default to OFF
when the K3 is turned on.

That way, if a person accidentally forgets to turn VOX OFF 
when he shuts the
radio down, it will automatically turn itself OFF next time 
you turn the K3
on.  On my radio, if I want to transmit after I turn the 
radio ON, I have to
re-select VOX ON again.>>>

This does not solve or change the problem.

The problem is, when the radio boots up, the amplifier relay 
control line is pulled low during the very early part of the 
power up. This happens in any mode with any VOX setting.

The situation this creates is if an external power amp with 
step-start is connected, some amplifiers go into quiescent 
current (TX relay closure) when the radio is powering up. 
This false triggering of the PA relay can cause an amplifier 
inrush circuit to be damaged.

For example the Drake L4B would would try to draw about 500 
additional watts through the step-start if the TX line was 
held low on amplifier power up if the radio is booting at 
the same time. Seeing all my TX indicators illuminate and 
hearing relays click when I power up the K3 is more of an 
annoyance to me, because my amplifers are designed to be in 
any keying state on power up without damage. On some 
amplifiers though, it can actually hurt components if they 
are held in TX mode while powering up.

I think the burden of design fault is in the amplifier, 
there should be no relay line state that causes or allows 
damage on power up, but the radio boot behavior is a little 
annoying. It might be some I/O areas like the relay control 
just fault into a TX mode before the system is booted, and 
there may be no way around that.

73 Tom