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Possible firmware regression related to ACC2 IO / PTT=LO

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K7MJG

Possible firmware regression related to ACC2 IO / PTT=LO

Hello,

In my setup, I use the KX3 as a receiver (only) and a TS-590s as a 100 watt transmitter. (Until the KXPA100 comes out.) To prevent damage to the KX3 receiver while transmitting 100W from the TS-590, I have connected the 590 to the ACC2 port of the KX3 and set the ACC2 IO to PTT=LO. This has worked well for me so far. When the 590 is keyed up, the KX3 goes into transmit (with the TX light illuminated) and the receiver is shut off.

However, recently, (probably with the latest 1.30 firmware release), I see something strange and certainly dangerous to my KX3. When I key up the 590 (a quick dit with 5 watts – the minimum), the KX3 TX light goes on, but I can see what I am transmitting (CW) on my CW Skimmer screen! I can tune the 590 to other frequencies and CW skimmer follows the 590’s TX frequency. This tells me that the KX3 is actually receiving what I’m transmitting with the 590 even though the TX light is on and the RX should be disabled. Note that the KX3’s S-meter is not deflected (no apparent signal).

Can someone (possibly one of the firmware engineers at Elecraft) tell me if a recent behavioral change was made to the ACC2 PTT controls? If the change was intentional, is there an alternate mechanism to satisfy my use case?

73,

Mark Glenn

K7MJG

wayne burdick

Re: Possible firmware regression related to ACC2 IO / PTT=LO

Administrator

No intentional change was made to this, Mark.

Please try activating the PTT=LO function of ACC2 manually, by
shorting the signal to ground. If that works correctly, but it doesn't
work from your 590's keyline, then I'd suspect the connection.

73,
Wayne
N6KR

On Dec 14, 2012, at 9:05 PM, K7MJG wrote:

> Hello,
>
>
>
> In my setup, I use the KX3 as a receiver (only) and a TS-590s as a
> 100 watt
> transmitter. (Until the KXPA100 comes out.) To prevent damage to
> the KX3
> receiver while transmitting 100W from the TS-590, I have connected
> the 590
> to the ACC2 port of the KX3 and set the ACC2 IO to PTT=LO. This has
> worked
> well for me so far. When the 590 is keyed up, the KX3 goes into
> transmit
> (with the TX light illuminated) and the receiver is shut off.
>
>
>
> However, recently, (probably with the latest 1.30 firmware release),
> I see
> something strange and certainly dangerous to my KX3. When I key up
> the 590
> (a quick dit with 5 watts - the minimum), the KX3 TX light goes on,
> but I
> can see what I am transmitting (CW) on my CW Skimmer screen! I can
> tune the
> 590 to other frequencies and CW skimmer follows the 590's TX
> frequency.
> This tells me that the KX3 is actually receiving what I'm
> transmitting with
> the 590 even though the TX light is on and the RX should be
> disabled. Note
> that the KX3's S-meter is not deflected (no apparent signal).
>
>
>
> Can someone (possibly one of the firmware engineers at Elecraft)
> tell me if
> a recent behavioral change was made to the ACC2 PTT controls? If
> the change
> was intentional, is there an alternate mechanism to satisfy my use
> case?
>
>
>
> 73,
>
> Mark Glenn
>
> K7MJG
>
>
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/Possible-firmware-regression-related-to-ACC2-IO-PTT-LO-tp7567198.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
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K7MJG

Re: Possible firmware regression related to ACC2 IO / PTT=LO

Wayne,

Thank you for taking the time to reply on a weekend.

I'm not an EE, so I could have flubbed this test, but here is what I did: With ACC2 IO PTT=LO, KX3 power output set to 0.0W, and CW Skimmer monitoring the RX I/Q from the KX3, I plugged a brand new plug into the end of the short ACC2 cable supplied with the 'KX3-PCKT Cable Set' (no connection to the 590), then shorted the tip to the sleeve. The KX3 TX light came on as expected. I keyed up a short dit on the 590 at five watts (into a dummy load, for the record) and was able to see the dit show up on the CW Skimmer screen at the 590 TX frequency.

Curiously, when I went to the KX3 right after reading your post, I could not immediately recreate the behavior. With no intentional change to the setup, it started happening again, which is when I did the experiment above.

Let me know how you'd like me to proceed. I can try to load older versions of the firmware, but I'll wait for your recommendation.

73,
Mark Glenn
K7MJG

wayne burdick

Re: Possible firmware regression related to ACC2 IO / PTT=LO

Administrator

Mark,

When the KX3 is placed in transmit mode, it doesn't disable its RX I/Q
outputs. These come directly from the receive mixer. Since the KX3's
local oscillator is still active in transmit mode, too, a really
strong signal (one that gets around the T/R switch) could still give
you a strong enough response at the I/Q outputs to be decoded. It
might vary with relative positions of the equipment, cables, etc.

You should be able to prevent the decode by putting the KX3 into SPLIT
mode, with VFO B moved well out of the target band. This way the LO
would be shifted in transmit mode so that any decode would be out of
the range of Skimmer.

For example if you're on 20 meters, set VFO B to well below the band
edge, say 13.8 MHz.

Let me know if this works.

73,
Wayne
N6KR

On Dec 16, 2012, at 5:13 PM, K7MJG wrote:

> Wayne,
>
> Thank you for taking the time to reply on a weekend.
>
> I'm not an EE, so I could have flubbed this test, but here is what I
> did:
> With ACC2 IO PTT=LO, KX3 power output set to 0.0W, and CW Skimmer
> monitoring
> the RX I/Q from the KX3, I plugged a brand new plug into the end of
> the
> short ACC2 cable supplied with the 'KX3-PCKT Cable Set' (no
> connection to
> the 590), then shorted the tip to the sleeve. The KX3 TX light came
> on as
> expected. I keyed up a short dit on the 590 at five watts (into a
> dummy
> load, for the record) and was able to see the dit show up on the CW
> Skimmer
> screen at the 590 TX frequency.
>
> Curiously, when I went to the KX3 right after reading your post, I
> could not
> immediately recreate the behavior. With no intentional change to
> the setup,
> it started happening again, which is when I did the experiment above.
>
> Let me know how you'd like me to proceed. I can try to load older
> versions
> of the firmware, but I'll wait for your recommendation.
>
> 73,
> Mark Glenn
> K7MJG
>
>
>
> --
> View this message in context: http://elecraft.365791.n2.nabble.com/Possible-firmware-regression-related-to-ACC2-IO-PTT-LO-tp7567198p7567268.html
> Sent from the Elecraft mailing list archive at Nabble.com.
> ______________________________________________________________
> Elecraft mailing list
> Home: http://mailman.qth.net/mailman/listinfo/elecraft
> Help: http://mailman.qth.net/mmfaq.htm
> Post: mailto:[hidden email]
>
> This list hosted by: http://www.qsl.net
> Please help support this email list: http://www.qsl.net/donate.html

K7MJG

RE: Possible firmware regression related to ACC2 IO / PTT=LO

Wayne,

Thanks for the great operating tip and for the explanation of the data path. Split works very well and keeps the CW Skimmer output pristine.

For my own peace of mind – Can I assume, then, that it is safe to transmit 100 watts into a transmit antenna approximately 20 feet from the KX3’s separate receiving antenna, and that as long as the KX3’s PTT is activated and the KX3’s TX light is illuminated, I’m not doing damage to my KX3?

Incidentally, I’m very much looking forward to the KXPA100 and will be one of the first in line to order it once it is announced.

Best regards,

Mark Glenn

K7MJG

From: wayne burdick [via Elecraft] [mailto:[hidden email]]
Sent: Sunday, December 16, 2012 6:30 PM
To: K7MJG
Subject: Re: Possible firmware regression related to ACC2 IO / PTT=LO

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wayne burdick

Re: Possible firmware regression related to ACC2 IO / PTT=LO

Administrator

K7MJG wrote:

> Thanks for the great operating tip and for the explanation of the
> data path.
> Split works very well and keeps the CW Skimmer output pristine.

Great!

> For my own peace of mind - Can I assume, then, that it is safe to
> transmit 100
> watts into a transmit antenna approximately 20 feet from the KX3's
> separate
> receiving antenna, and that as long as the KX3's PTT is activated
> and the KX3's
> TX light is illuminated, I'm not doing damage to my KX3?

Putting the rig into TX mode is a very effective strategy for
protecting the front end. I'd feel better if the antennas were farther
apart, but you seem to have an existence proof.

Wayne
N6KR

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