TX Inhibit options

[cqbilld]

  I have broken the PTT line in the mike to operate the sequencer input (also have an external toggle switch to operate the sequencer as well.) The sequencer then operates the K3 PTT. This has worked very well on several different IF radios over the years. The K3 PTT line on the front panel mike connector of the K3 is unused. This has worked very well EXCEPT on 6m when I run the amp on SSB. When the mike connector is connected, RF gets back into the K3 and it has a low freq power oscillation. The watt meter looks like a flag waving! If I back off the power on the amp to 100w or less (K3/10 with external PA) I all is fine, so I just run it at reduced power for SSB. On WSJT I run with the mike connector disconnected and all is fine at any power level. (rear panel audio to/from the sound card) This RF feedback issue causes the power to fluctuate at a low freq and is not the typical RF garbage often heard on the bands.

  The problem comes and goes and I have tried clamp on ferrite beads on EVERYTHING without a good fix. The sequencer/K3 PTT line was originally twisted pair hookup wire, but is now a shielded cable with no change. Perhaps this is a "Pin 1" issue... I am guessing a ground loop of some kind. Goofy non the less.  For more info .... http://www (dot) qth (dot) net/k0awu/K3System.html

  Good luck and 73  ... Bill   K0AWU  EN37ed

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----- Original Message -----
From: "Roger Banks" <[hidden email]>
To: [hidden email]
Sent: Wednesday, June 29, 2011 4:36:29 AM
Subject: [Elecraft] TX Inhibit options

Hi All.
I am using a K3 with internal 144 transverter module.
On 2m I use a sequencer for TX/RX as I use a PA and a LNA at the masthead.
The rig TX is triggered by the sequencer by using the PTT In line.
The sequencer ensures the rig is switched after the LNA. The sequencer is
triggered either by a foot switch or by the signalink Data line.
The problem I have is that there is a HUGE risk (and I have done it) of
inadvertantly using the manual TX button on the front of the K3. If this is
done the rig goes to TX and teh sequencer is bypassed - thus blowing the
LNA.. ouch.
This issue is compounded by the fact that on all other bands I need
conventional operation of the ring as there is obviously no problem with
sequencers elsewhere and you get used to using eiher ptt or the tx button.
Question then - is there a way of disabling/inhibiting the TX button/ mic
socket ptt on the rig just on 2m so that on 2m you can only instigate TX via
the back panel PTT in line?
Help appreciated!
Roger Banks
GW4WND

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