[Elecraft] K2 - Power dropping off on higher bands (?)

[John R. Lonigro]

Dave:

The first thing to check is the voltage going to your radio. If you are 
using a 12 volt battery, those numbers might be OK. With 13.8 volts, Ron 
is right that you should get at least 10 Watts on 10M. If you are using 
a 13.8 volt supply, check the voltage at the rig using the built-in 
voltmeter on receive and transmit. If the voltage drops considerably on 
transmit, the gauge of the wire providing 13.8 volts to your radio might 
be too small. After going through D10, the voltage reading on the 
display won't be 13.8 volts, but that's not a problem. In playing around 
this evening, I found a difference of about 1.2 volts between transmit 
and receive and couldn't get close to 10 Watts on 10M. A shorter cable 
brought the voltage difference down to about 0.3 volts and the power out 
to 10Watts on 10M. I need a bigger gauge power cable.

I just read your follow-up email and think your numbers are probably OK 
with the lower supply voltage. Try 13.8 volts if you have it available. 
If you still don't get satisfactory results, then check out the wire as 
per above.

Good luck.

John AA0VE


Ron D'Eau Claire wrote:

>No, that's not "normal". While the power does drop off on the higher bands,
>it should be at least 10 watts on the lowest band (usually 10 meters). 
>
>What does the K2 say it is making in RF output into your dummy load? 
>
>The K2 Power Metering is really quite good when working into a good
>non-reactive 50 ohm load, but most importantly, the K2 adjusts its output
>power to what the internal metering circuit says it is getting. That is,
>when you set POWER to 10 watts, the power control circuit holds to power
>down to what the Internal Meter says is 10 watts. 
>
>The power indicated on the display when you adjust the POWER control is the
>REQUESTED power. The K2 may or may not be able to provide it all. 
>
>Ron AC7AC
>
>
>-----Original Message-----
>Thought it might be a good idea to find out the max drive power on each
>band, and here's what I found tonight (power control turned full clockwise):
>
>3700MHz   -   15 watts
>7100MHz   -   15 watts
>10100MHz -   14 watts
>14100MHz -   13 watts
>18113MHz -   13 watts
>21200MHz -   11 watts
>24950MHz -   9.5 watts
>28350MHz -   8 watts
>
>  
>