Key Line protection for MFJ-1026 Noise Cancelling Unit

[pentrose]

I am trying to use an MFJ-1026 "Noise Canceling Signal Enhancer" with my KX3 serial #08668.
The MFJ unit has a T/R phone jack for protecting its circuits from RF currents when transmitting.

Q: The voltage seems to be too high according to the Cady book.  I need to use the Key Line to signal the MFJ unit to bypass sensitive circuits during transmission.

Pg 150 of the Elecraft KX-Line Fred Cady book says the ring has +30 volts on the circuit when open.  The MFJ-1026 Manual says to never put over 15v positive to the T/R phone jack?

From the MFJ-1026 Manual
“T/R Control: We Strongly recommend using this phono connector to switch the MFJ-1026 to the transmit (or bypass) mode.  The MFJ-1026 switches out-of-circuit whenever this line is pulled low (below one volt).  
Never apply negative voltages, or over 15 volts positive, to this jack.”

I have the E980232 Cable adaptor with Key Line information on the Ring.  I think I could use the phone jack to send the low signal through the Ring.  But when it opens up the voltage is too high?

Also, am I on the right track here?  Other ways to do this?  I am not qualified to create my own circuits.
can I just run a phone jack from the adaptor plugged into the ACC2 port?  Provided I can deal with the +30 volts?  I have the KXPA 100 Amplifier and no other amplifiers.  This is all I want or need. So the antenna 1 line would run from the KX3 into the MFJ-1026 and then to the 100 watt amplifier.  Is this right?

Peder Kittelson W7RPK

[Don Wilhelm]

Peder,

Please re-read that part in the Cady manual again.
What it *should* say is that the KX3 Keyline output will *tolerate* up
to +30 volts open circuit.
To convince yourself if necessary,  connect nothing to the KEYLINE
output jack except your DMM.  It should read zero voltage.  Then set the
DMM to read resistance - the resistance should be high, even infinite.
When the KX3 goes into transmit, the resistance should be quite low,
even zero.

The Keyline output is an open drain FET and produces no voltage by
itself - the voltage is produced by the device connected to it.

Measure the open circuit voltage of the KEYLINE *input* on the MFJ unit.
  In other words, do not connect anything to the T/R phone jack and
measure the voltage with your DMM.  If it is less than 30 volts, it can
be used with the KX3.

73,
Don W3FPR

On 3/27/2017 4:52 PM, pentrose wrote:

> I am trying to use an MFJ-1026 "Noise Canceling Signal Enhancer" with my KX3
> serial #08668.
> The MFJ unit has a T/R phone jack for protecting its circuits from RF
> currents when transmitting.
>
> Q: The voltage seems to be too high according to the Cady book.  I need to
> use the Key Line to signal the MFJ unit to bypass sensitive circuits during
> transmission.
>
> Pg 150 of the Elecraft KX-Line Fred Cady book says the ring has +30 volts on
> the circuit when open.  The MFJ-1026 Manual says to never put over 15v
> positive to the T/R phone jack?
>
> From the MFJ-1026 Manual
> “T/R Control: We Strongly recommend using this phono connector to switch the
> MFJ-1026 to the transmit (or bypass) mode.  The MFJ-1026 switches
> out-of-circuit whenever this line is pulled low (below one volt).
> Never apply negative voltages, or over 15 volts positive, to this jack.”
>
> I have the E980232 Cable adaptor with Key Line information on the Ring.  I
> think I could use the phone jack to send the low signal through the Ring.
> But when it opens up the voltage is too high?
>

______________________________________________________________
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
Message delivered to [hidden email]

[pentrose]

Don, that would be such great news.  
I am re-reading the chart on page 150 and it does not use the word Tolerate.

Peder W7RPK

[Don Wilhelm]

I guess I should have said something more like "that is the maximum
permissible voltage that can be safely applied from an external device".
It is the recommended operating voltage for the driving FET in the KX3.

73,
Don W3FPR

On 3/27/2017 5:26 PM, pentrose wrote:
> Don, that would be such great news.
> I am re-reading the chart on page 150 and it does not use the word Tolerate.
>
> Peder W7RPK
______________________________________________________________
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
Message delivered to [hidden email]

[pentrose]

OK!  Super.  I will proceed on that.

Thanks for your patience.  I know that language must be exact in this world.  Yet, I don't want to put you into needless work.

Final Question: Is there any downside for me to use the E980232 adapter in my situation?  It looks to me like the ACC2 port is mainly used for Linear Amplifiers and other things like it in signaling.  And I like the KXPA 100 amplifier as it is already running.  I love that it automatice turns on with the KX3 and makes other adjustments as well.  The KX3 is working great.

Am I right that for me, nothing is changed in functionality?


Peder W7RPK

[Don Wilhelm]

Peder,

That output is KEYLINE OUT and can be used for *any* device - amplifiers
are most common.
If you have more than 2 devices connected to that KEYLINE output, there
may be a voltage conflict between your external devices - the open
circuit voltages for the different devices may be different and cause
current to flow from one device to another.
Note that this is not a KX3 problem, it is a problem between the
multiple devices external to the KX3.

Nothing should change in the KX3 functionality due to the KEYLINE OUT.

73,
Don W3FPR

On 3/27/2017 5:50 PM, pentrose wrote:

> OK!  Super.  I will proceed on that.
>
> Thanks for your patience.  I know that language must be exact in this world.
> Yet, I don't want to put you into needless work.
>
> Final Question: Is there any downside for me to use the E980232 adapter in
> my situation?  It looks to me like the ACC2 port is mainly used for Linear
> Amplifiers and other things like it in signaling.  And I like the KXPA 100
> amplifier as it is already running.  I love that it automatice turns on with
> the KX3 and makes other adjustments as well.  The KX3 is working great.
>

______________________________________________________________
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
Message delivered to [hidden email]