KX3/KX2 voltage display

[Erik Tkal]

When using the special VFO B display to show the supply voltage, both my KX3 and KX2 disagree with the rest of my equipment.  The radios consistently are 0.2V - 0.4V lower than my inline meters and my Fluke when measured at my RigRunner distribution block and at the end of a cable (e.g. if I disconnect my PX3).  I don’t see any way to calibrate this, is this expected?

  Thanks and 73,
  Erik Tkal  -  W1QED

______________________________________________________________
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]

[Lyle Johnson]

Hello Erik!

Yes, it is expected.  There is low-drop diode in series with incoming
power to protect the radio circuitry from reversed polarity at the power
connector.  The typical voltage drop is about 0.3V at nominal current.  
The internal "12V" supply voltage being reported is after the diode's
voltage drop.

Both radios share this characteristic.

73,

Lyle KK7P


On 1/2/17 10:46 AM, E T wrote:
> When using the special VFO B display to show the supply voltage, both my KX3 and KX2 disagree with the rest of my equipment.  The radios consistently are 0.2V - 0.4V lower than my inline meters and my Fluke when measured at my RigRunner distribution block and at the end of a cable (e.g. if I disconnect my PX3).  I don’t see any way to calibrate this, is this expected?
>
>    Thanks and 73,
>    Erik Tkal  -  W1QED

______________________________________________________________
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]

[Don Wilhelm]

Erik,

The KX3 and KX2 (and K3, K3S and K2) display the voltage AFTER the
reverse polarity protection diode.  That is the actual operating voltage
of the transceiver.
The Shottky diode typically drops about 0.3 volts, so the internal
measurement will be about 0.3 volts lower than a voltage measurement
external to the transceiver.

73,
Don W3FPR

On 1/2/2017 12:46 PM, E T wrote:
> When using the special VFO B display to show the supply voltage, both my KX3 and KX2 disagree with the rest of my equipment.  The radios consistently are 0.2V - 0.4V lower than my inline meters and my Fluke when measured at my RigRunner distribution block and at the end of a cable (e.g. if I disconnect my PX3).  I don’t see any way to calibrate this, is this expected?
______________________________________________________________
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]

[Erik Tkal]

Ok, thanks, that makes sense.  One of my SLA maintenance chargers was only keeping my external battery around 12.7V, so once in a while I’d get the LO SUPPLY indicator when charging the internal batteries.  I just switched over to a different one (Black & Decker) that keeps the SLA closer to 13.8.  Of course when I use my PowerWerx supply I can set that to anything… :-)

  Thanks and 73,
  Erik Tkal  -  W1QED

On Jan 2, 2017, at 12:59 PM, Lyle Johnson <[hidden email]> wrote:

Hello Erik!

Yes, it is expected.  There is low-drop diode in series with incoming power to protect the radio circuitry from reversed polarity at the power connector.  The typical voltage drop is about 0.3V at nominal current.  The internal "12V" supply voltage being reported is after the diode's voltage drop.

Both radios share this characteristic.

73,

Lyle KK7P


On 1/2/17 10:46 AM, E T wrote:
> When using the special VFO B display to show the supply voltage, both my KX3 and KX2 disagree with the rest of my equipment.  The radios consistently are 0.2V - 0.4V lower than my inline meters and my Fluke when measured at my RigRunner distribution block and at the end of a cable (e.g. if I disconnect my PX3).  I don’t see any way to calibrate this, is this expected?
>
>   Thanks and 73,
>   Erik Tkal  -  W1QED

______________________________________________________________
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]

______________________________________________________________
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]

[Elecraft mailing list]

> On Jan 2, 2017, at 2:04 PM, E T <[hidden email]> wrote:
>
> I just switched over to a different one (Black & Decker) that keeps the SLA closer to 13.8.  Of course when I use my PowerWerx supply I can set that to anything… :-)

But do not turn on the PowerWerx while the KX3 is running or you'll receive a nasty surprise.  There's a strong voltage spike from the PowerWerx that overwhelms the KX3 and the KX3, in response, shuts down.   If you plan to use the SLA as backup while mains power fails, be sure to turn off the PowerWerx before mains power returns.

73,
Marc W8SDG



______________________________________________________________
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]