Posted by
John A. Ross [Ecraft] on
Jul 16, 2006; 9:17pm
URL: http://elecraft.85.s1.nabble.com/Weller-WTCPT-illuminated-rocker-switch-tp392187p392192.html
> -----Original Message-----
> From: Ron D'Eau Claire [mailto:
[hidden email]]
> Sent: Sunday, July 16, 2006 9:00 PM
> To: 'John A. Ross [Ecraft]';
[hidden email]
> Subject: RE: [Elecraft] What should the power output of the K2 be?
> Welcome to the K2-club John! I built mine in 2000. It's a FB rig.
Ron
Thanks, you are right, it is a very nice rig indeed and fantastic fun to
build and work on.
> The specified output of the K2 is at least 10 watts CW. The
> actual output varies with the band. It is a function of the
> overall transmitter path gain.
> It tends to peak about 40 meters, where most K2's will make
> 15 watts output, or very close to it. Up on 10 meters is
> where the overall gain is lowest and many K2's just barely
> make the specified 10 watts output.
> Since you're still getting familiar with your K2, here's a
> couple of things to remember:
>
> 1) The POWER control sets the "requested" power output. The
> K2 monitors the actual power output and adjusts the
> transmitter gain as needed for what you've requested. The
> control allows you to "request" any power up to 15 watts, but
> you can't get that much on all bands.
OK, that makes sense now. I was not sure if the sample/control loop was
doing something wrong. You never know when firmware has a part in it ;-)
> 2) Because the POWER control circuitry is monitoring the
> power output to determine how much gain the transmitter
> circuits should have, the accuracy of the output power
> setting depends upon how accurately the K2 measures its
> output. A basic QRP K2 uses a simple RF voltmeter to monitor
> the output. It is highly-dependent upon an accurate,
> non-reactive 50-ohm load for good accuracy. Any significant
> SWR at the transmitter output will affect it, and the actual
> power output. The (KAT2, etc.) ATU's use a bridge circuit
> that is a little more accurate, but can still be thrown off
> by reactive terminations.
I had not installed the ATU yet, Po was dumped into a DL-600 then checked
again on a 2955B so I am pretty sure the loads were OK.
> 3) If you change the POWER control setting you have to
> transmit before the new power level takes effect, since the
> K2 must sense the output RF to tell how to adjust the
> circuits. That means that you may notice that the output is
> nearly zero when you hit the first dit or dah after turning the K2 on.
> It'll immediately jump up to whatever you have the control
> set for. The same is in reverse when you turn the power down.
> The first time you touch the key the power will still be up
> at the old higher level until there's RF for the circuit to sense.
OK, clear now.
> 3) The K2 is rated at 10 watts PEP on SSB, regardless of how
> much it will produce. That's because the distortion
> increases above 10 watts PEP in SSB mode. CW doesn't need a
> linear amp, so it's not an issue when you're pounding brass,
> but don't exceed 10 watts PEP on SSB on any band.
>
> 4) The Bargraph power display is in peak power, so it'll show
> flickers at the PEP peaks instead of the average power like
> most inexpensive external meters. That cause confusion
> sometimes when the opr notices that his external meter is
> wiggling around at 3 or 4 watts while his K2 shows 10 watt
> peaks on SSB. That's normal. The external meter is showing
> the average output, not the peak.
Cheers Ron
All best
John
>
> Ron AC7AC
>
>
>
> -----Original Message-----
>
> Hi all
>
> I have been having great fun with the K2 but I am wondering
> what the output should be?
>
> 10W or 15W?
>
> The Po control seems to indicate 15W should be possible.
>
> The PA alignment seems OK, or at least as per the manual,
> Po/current seems to match at the levels stated.
>
> But occasionally the built in detector seems to read a little
> higher than the Po is set to and the full scale setting of 15
> only seems to yield 11w or so.
>
> As this is the only one I have built so far I am curious.
>
> Any guidance appreciated.
>
> John
>
>
>
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