K3 current status of TX INH?

[Jerry_N8BM]

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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[GW0ETF]

Jerry.Van wrote

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.

Quote from the Acom 1000 manual...

" e) The KEY-OUT socket on the rear panel provides an extra control signal from the amplifier to the transceiver. It could be used to improve the transmit/receive switching safety.

If your transceiver has a suitable input that disables transmission, we recommend that you connect it with a cable terminated in a Phono (RCA) connector to the KEY-OUT socket of the amplifier. Transceiver producers give different names to this input and they are for instance TX-INHIBIT, MUTE, LINEAR, etc. Check your transceiver's manual or consult your dealer.

If your transceiver does not have such input, don't worry - the amplifier will function normally as well, and then the KEY-OUT may remain unused. "

Does this constitute a recommendation?

Take your pick.

73,

Stewart, GW0ETF

(K3 #145 with Acom 1000 in qsk with single keying line)

[Barry N1EU]

Hmmm, which part of "we recommend that you connect it" does not constitute a recommendation?

I understand that many of you K3 owners are happily using the K3 and Acom/Alpha/TenTec amplifier without a keying loop and I'll be joining your ranks momentarily.  But this does not obviate the benefit of adapting the K3 and supporting the keying loop interface.  The benefits of doing so have already been stated.

73,
Barry N1EU

GW0ETF wrote

. . . If your transceiver has a suitable input that disables transmission, we recommend that you connect it with a cable terminated in a Phono (RCA) connector to the KEY-OUT socket of the amplifier. . .

Does this constitute a recommendation?