[Elecraft] [K1] K1 Low power, Suggestion to increase output power

[Don Wilhelm]

Rick,

Certainly - to measure any LPF, here is how to do it, along with the K1 
band board pin information:
In general, you just isolate the LPF, terminate one side and scan the 
other side with the antenna analyzer.  Conceptually it is easy.
What gets complicated is how to isolate the LPF - it differs from one 
radio to another.  For the K1, you must remove the band board AFTER 
setting the band to the one to be scanned - fortunately there are 
latching relays.
After the band board is removed, connect a 51 ohm resistor between pins 
2 and 3 of P3 - then devise a means of connecting the antenna analyzer 
to pin 9 (or 10) of J2 and ground.

Making those connections will depend on what one has in the shack - 
certainly the resistor could be soldered to the solder side of  P3 and a 
short piece of coax (inches long) can be soldered onto the solder side 
of J2, but there are other means if one has some header material lying 
around to make up a temporary fixture that can simply be plugged to the 
board.

Having made the connections, then the analyzer is scanned over the band 
of interest observing the SWR - it should be low, and should climb as 
the frequency is increased above the band, and should be quite high at 
the 2nd harmonic of the lower band edge.

For the KAT1, it includes a wattmeter, but that must be calibrated to 
read the correct power - the K1 uses the wattmeter output to control the 
actual output power, so it is natural that the K1 LCD bargraph agrees 
with the OUT setting.  You can calibrate the wattmeter simply by making 
it match whatever external wattmeter you have, or use something more 
accurate, like the detector on the Elecraft DL1.  Be aware that there is 
a lot of discrepancy in wattmeter readings, and I don't trust many of 
them until they have proven their accuracy.  I do have several tools 
that can be used for that task, but my most basic 'instrument' is a 
known good 50 ohm dummy load that is flat over the frequency range to be 
used.  I read the RF voltage across the dummy load with my oscilloscope 
and a 10X probe, then compute the power - it is quick and easy because 
the 'scope reads peak to peak RF voltage and the formula for power 
reduces to V^2/8*R or V^2/400 for a 50 ohm load - easy and quick to 
punch the numbers in on a calculator.
I have posted that formula derivation on the reflector before, so now if 
anyone wants to check it, you can derive your own or check the archives 
- Hint: use the exact expression sqrt2/2 when reducing the formula for 
RMS conversion, if you try it with 0.707 you will go nuts (the sqrt2 
terms drop out when the formula is reduced).


73,
Don W3FPR

Rick/WA6ES wrote:
> Byron
>   I am using the meter on the K1. I also have an MFJ Tuner/meter combo for
> QRP that is not that accurate. I will be purchasing a new meter soon. Not
> sure about the KAT1 issue, that is my next purchase along with the Battery
> pack. Maybe Don/W3FPR could help answer this.
>
> Don
>   Yes please tell me how to read the cut off Freq. I have the MFJ type.
>
> Thanks
> Rick/WA6ES
>
>
> Byron Servies-2 wrote:
>   
>> On Jan 4, 2010, at 9:02 PM, Rick/WA6ES wrote:
>>
>> How are you measuring the power output?
>>
>> With my new K1 using a DL1 and KAT1 I get exactly the number of bars on
>> the TX LCD bar graph as I set in the output menu for power output using a
>> 13.8 vold power supply, from 2 to 7.  This is true for all 4 bands, with
>> the only difference being if I don't tune it takes a few CQ's for the KAT1
>> to catch up, as expected.
>>
>> Just curious what I might be missing,
>>
>> Byron KI6NUL
>>     
>