[Elecraft] K3 Field Day Note: QRO/Battery

[wayne burdick]

The K3 can be used at QRO power levels (13-120 W) when powered from a 
car battery or a large gel cell. Here are a few things to keep in mind:

- A battery that's significantly discharged will have higher internal 
resistance, which will cause the voltage to drop when high current is 
drawn. (Small-gauge battery cables should also be avoided.)

- You can monitor your battery's vital signs during RX and TX using the 
K3's built-in voltmeter and ammeter. Just tap DISP, then rotate VFO B 
to see the voltage or current.

- The specified minimum supply voltage for the K3 is 11 V. This is a 
conservative rating, intended to ensure spectral purity and stability. 
But maximum power output will drop almost linearly with supply voltage. 
You'll typically get 120 W at 13 V, 100 W at 12 V, and about 75 W at 11 
V. At 10.5 V, you should drop to QRP levels. Below 9.5 V the rig may 
turn itself off. Reduce the power setting manually when voltage drops, 
just to be safe.

- If you see an unexpected "HI TEMP" warning during QRO transmit, it 
could be due to an excessive dip in battery (or generator) voltage at 
the PA monitor circuitry. If you see this happen, try configuring the 
temperature sensor to sample only during receive mode. To do this, 
locate the PA TEMP menu entry (CONFIG menu), then tap the '1' key until 
you see "R ONLY" (rather than the default, "T AND R"). This mode of 
operation is completely safe as long as you're not "standing on the 
key" for several minutes at a time.

73,
Wayne
N6KR


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