K3 LONG delay in TX after TXINH removed

[Mark n2qt]

I have TXinh sent to my K3 to ensure it doesn't transmit during initial
keying or during antenna relay
switching.  In my setup TXINH is removed about 8 ms after the K3 is keyed.
However, it looks like
it takes the k3 about 450 ms or so after TXINH is removed for the k3 to make
power output.  This
of course really messes up my cw output as it kills the first character.  It
also occurs with manual
Tune from the front panel or with other modes, so not just on CW.

I don't see menu items that would cause this.  Anyone else seeing this?

I 'think' this used to work, but I haven't tried old firmware to verify if
my memory is correct.  Since the
160 contest is tonight, I'll just pull the TXinh and live on the edge.

Mark n2qt


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[Mark n2qt]

My TxInh circuit diode or'd various inputs together.  What I did not do is
put a
resistor to ground after the diodes.  The K3 TxInh input does not have a
pull
down, and has a high enough impedance that there is an appreciable time
delay before the TxInh coasts down to where it allows the K3 to transmit.

Adding the resistor makes everything ok again...

Mark n2qt

-----Original Message-----
From: Mark n2qt
Sent: Friday, January 25, 2013 5:23 PM
To: [hidden email]
Subject: [Elecraft] K3 LONG delay in TX after TXINH removed

I have TXinh sent to my K3 to ensure it doesn't transmit during initial
keying or during antenna relay
switching.  In my setup TXINH is removed about 8 ms after the K3 is keyed.
However, it looks like
it takes the k3 about 450 ms or so after TXINH is removed for the k3 to make
power output.  This
of course really messes up my cw output as it kills the first character.  It
also occurs with manual
Tune from the front panel or with other modes, so not just on CW.

I don't see menu items that would cause this.  Anyone else seeing this?

I 'think' this used to work, but I haven't tried old firmware to verify if
my memory is correct.  Since the
160 contest is tonight, I'll just pull the TXinh and live on the edge.

Mark n2qt


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[Don Wilhelm-4]

Mark,

It is good to hear that the resistor solved the problem.

If you had to add a pull-down resistor, that is not a K3 problem, that
is a requirement of whatever in your sequencer that is driving the K3 TX
INH line.  In other words, whatever is driving your TX INH line is not
going to zero volts quickly enough.
Since you have several units diode ORed for TX INH, it could be any one
of them causing the situation.

It is nice to hear that you have found a solution.

73,
Don W3FPR

On 1/26/2013 5:37 PM, Mark n2qt wrote:
> My TxInh circuit diode or'd various inputs together. What I did not do
> is put a
> resistor to ground after the diodes.  The K3 TxInh input does not have
> a pull
> down, and has a high enough impedance that there is an appreciable time
> delay before the TxInh coasts down to where it allows the K3 to transmit.
>
> Adding the resistor makes everything ok again...
>

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