Thanks for the response Dave. Yes the Acom (and other amps w. qsk
keying
loops) will work well without TX EN/INH wired. But Acom recommends
using it
whenever possible. It provides not only a safety valve to cutoff the
transmitter instantly when there's a serious fault in the amp, but also
potentially provides improved qsk if the transceiver's timing fully
supports
the keying loop.
I was just informed of a reflector posting of Dec 23 that I must have
missed
(apologies) from Jerry N8BM at
http://mailman.qth.net/pipermail/elecraft/2007-December/079341.html
It's obvious upon reading Jerry's posting that an amplifier keying loop
function is NOT yet implemented on the K3, despite the firmware change
to TX
INH - there's currently no way to get the K3 out of inhibit mode and
begin
xmsn if it ignores PTT/key input while in inhibit mode.
So all we can do is wait and hopefully Elecraft will eventually announce
that they have indeed implemented support for amplifier keying loop in a
new
firmware update.
73,
Barry N1EU
---------------------
Barry,
Thank you for your most welcome post and the mention of my December
post. I agree with you wholeheartedly and I'd like to take the
opportunity to post a possible solution that both of us seem to share.
I am thinking that a 3rd parameter for TX INH could be implemented.
Let's call it "TX INH - KEY LOOP" or whatever. When that function is
selected it will perform in a similar manner as HI=INH except that the
K3 will be allowed to transmit by its normal mechanisms. The sequence
would be; key the K3, KEY OUT on the K3 goes low, a low being sensed at
the amp's KEY IN would start the amp's internal sequence and when that
sequence is completed the amp's KEY OUT line goes low, the amp's KEY OUT
line (connected to the K3's TX INH port) which is now low causes the K3
to start sending RF immediately and without it's normal 10-15 ms. delay.
In the situation (and Barry seems to agree) where the amp's KEY OUT line
goes high while the K3's KEY OUT is still low I am thinking that the amp
is sensing some problem either internally within itself or some external
problem in which case the K3 should immediately drop RF and cause it's
KEY OUT line to go high. Finally, it would appear that some sort of
pull-up will be required which could be added by Elecraft or a user
following a procedure outlined by Elecraft.
I do hope that Elecraft will further consider the implementation of an
amp keying loop. While I realize that a key loop amp will key with or
without a keying loop I would prefer following an amp manufacturers
recommendation when they suggest its use.
Jerry N8BM
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