[Elecraft] K3 TX delay

[Edward R. Cole]

Don and Igor,

I didn't think it out completely when I first posted.  This is 
because this is the first time I will use a HF amp.  VHF amps nearly 
all have RF sensed TR (Plus the means for PTT control).  I do not 
like RF sensing as I can not see how one avoids hot switching.

MY system for running the HF amp will be using a good old toggle 
switch (same function as a foot switch).  That will  the K3 PTT 
(KEYIN) and the control the amp PTT (KEYOUT) before I ever touch the 
CW key.  For SSB there is no issue since PTT switching will be 
accomplished before I speak (thus producing RF).  I cannot use that 
for AM or FM but I have not used FM on 10m so not an issue (at this 
point).  The only thing I will have to check is if paralleling my 
sequencer input with the amplifier PTT will cause any control issues 
(both using pull-up +13.7v and grounding the PTT line).  Possible 
using some steering diodes will isolate them.  I don't want to have 
to remember to switch over anything.  On HF only the amp will use TR 
switching so pretty simple.  I will not have to lengthen the TX-DLY.

I haven't decided if I want to use inhibit for HF. It is implemented 
for VHF at present using the BAND0 control line to activate it.  I 
will add BAND1 (for 222) and DOGOUT1 (for 6m) to add inhibit on those 
two bands.  Probably do not need inhibit on HF (unless I am forgetful 
throwing the "toggle switch").  I have to do that for CW on VHF so 
probably become habit.

This should take the old-timers back to the days where we used a 
toggle switch marked SEND on the old receivers which applied voltage 
to the old Dowkey coax relay.  Those had aux contacts for grid-bias 
keying the old vacuum tubes transmitters.

Ed

------------------------------

Message: 6
Date: Fri, 17 Feb 2012 07:55:20 -0500
From: Don Wilhelm <w3fpr at embarqmail.com>
Subject: Re: [Elecraft] K3 TX delay

Igor,

I understand your situation, but the application of PTT does not produce
any RF - nothing will hot switch.
When you "hit the key" (or for SSB begin talking), then RF is produced.
If you arrange your switching to be accomplished by either the PTT or
the K3 KEYOUT, and leave the K3 in non-VOX state, there is no need to
increase TX DLY to any other than the 8 ms default value and therefore
no shortening of CW elements.

73,
Don W3FPR




73, Ed - KL7UW, WD2XSH/45
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