KX3 Operating Tip: Maximizing battery life in RX and TX modes

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KX3 Operating Tip: Maximizing battery life in RX and TX modes

wayne burdick
Battery life can be improved by minimizing the KX3's receive and  
transmit current drain.


The KX3 already has far lower receive-mode current drain than most all-
band/all-mode transceivers, but you can further reduce it in several  

   - use headphones (10-100 mA saved depending on volume level)
   - turn off the LCD backlight (25 mA)
   - turn off the RX I/Q port when not needed (10 mA; see MENU:RX I/Q)
   - turn off the preamp (5 mA saved for the 20 dB preamp,
     10-15 mA for the 10-dB preamp)
   - turn off the RX isolation amp (10-15 mA; see MENU:RX ISO)

Using all of the above techniques, receive-mode current drain can be  
as low as 150 mA, varying a bit per-band.


In transmit mode, current drain varies with power level, supply  
voltage, band, and load impedance. An antenna tuner (such as the  
internal KXAT3 option) can help ensure the transmitter sees a good  

There are some thresholds where the transmit current drain is  
automatically reduced by switching in a higher-impedance PA output  
transformer winding. In this case a decimal point is added to the  
right of the power display when you adjust it (e.g., "3.0 W."). Here  
are the conditions under which TX current is reduced:

1.  5.0 W or less in CW, FSK-D, and FM modes when key-down supply  
voltage is 11 V or higher

TX current in this case is typically 1 amp -- about 50% lower than  
what you'll see if you move power just a bit above 5.0 W. This is  
especially useful for QRP Field Day outings (etc.) where the rig is  
powered from an external 12 to 14 V battery.

2.  3.0 W or less in all modes, regardless of supply voltage

This is the generally recommended power level when operating from an  
internal NiMH battery pack. If you're more interested in power output  
than operating time, you can run up to 5 watts from the internal  

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