Weller WTCPT illuminated rocker switch

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[John A. Ross [Ecraft]]

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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[Ron D'Eau Claire-2]

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.

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.

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.

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.

Welcome to the K2-club John! I built mine in 2000. It's a FB rig.

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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[John A. Ross [Ecraft]]

> -----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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[Sam Morgan-2]

Ron D'Eau Claire wrote:

> 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.
>
This has always been a confusion factor for me.
So with an external meter,
running CW you should have it's scale set to peak or average?

And if you use the same meter on SSB
and do the long 'hello' thing,
which setting gives you the more accurate
(in relation to setting the output to say 10w) reading for a contest?

TIA
--
GB & 73's
KA5OAI
Sam Morgan
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[Don Wilhelm-3]

Sam,

There is no one single answer to your question because it depends on the
particular meter's response and will differ from one meter to another.

The K2 bargraph peaks will usually indicate the peak power more readily than
a 'peak reading' analog power meter.  The reason is that the bargraph
responds rapidly while the analog meter has mechanical mass to move and will
respond more slowly - 'damping factor' is the technical term.  Most meters
simply add an RC network to provide conversion from average to peak, but
there are many dependencies on the accuracy of that conversion.

To really determine the PEP level, the best instrument is a 'scope.  Connect
the 'scope (with a compensated 10X probe) across the load.  Then transmit CW
at the power level you wish to set the SSB PEP value at and note how far it
deflects on the 'scope.  Now transmit with SSB and make the peaks equal to
the deflection level you observed with the CW signal.  Once you have
determined the real PEP value for a certain power level, you can connect
your external power meter and see how far your voice deflects the meter with
that power level.

With CW, the Average Power and the Peak Envelope Power are equal, but with
SSB, the average power will be considerably less than the PEP - how much
less depends on the voice, the amount of copression, etc.  In any case, a 5
watt CW signal will contain considerably more power than a 5 watt SSB
signal.

73,
Don W3FPR


> -----Original Message-----
.

> >
> This has always been a confusion factor for me.
> So with an external meter,
> running CW you should have it's scale set to peak or average?
>
> And if you use the same meter on SSB
> and do the long 'hello' thing,
> which setting gives you the more accurate
> (in relation to setting the output to say 10w) reading for a contest?
>
> TIA
> --
> GB & 73's
> KA5OAI
> Sam Morgan
>

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