K1: power output gauge

[WB0OEW]

Hello all,

I've had K1 S/N 2594 on the air for a few months now and having a blast. Great transceiver. Thanks elecraft!

But I'm curious about the power output scale. I have Out set to 5 W. I'm on 40m. My antenna SWR is about 1.7:1 at 7.00
and 7.15 MHz and dips smoothly down each way to about 1.2:1 in the middle at about 7.08. However, the number of power
bars is 5 at each end of the band and 4 in the middle, just opposite of what I would expect given the SWR profile.
With the DL1 dummy load, it's 5 bars all across the band.

Yes, I read the power output accuracy disclaimer in the manual and I'm not complaining, just curious about this
behavior. No, I do not have the KAT1 antenna tuner.

Thanks much,

Elwood, WB0OEW, Socorro, NM


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[John Huggins]

One experiment to try is to transmit into a dummy load of 75 -100 or so
ohms.  The idea is to produce a consistent SWR other than 1:1 to see how
things behave in non-ideal, but consistent circumstances.  I am not sure
what you will see, but the results might help with understanding.

Elwood C. Downey wrote:

> Hello all,
>
> I've had K1 S/N 2594 on the air for a few months now and having a blast. Great transceiver. Thanks elecraft!
>
> But I'm curious about the power output scale. I have Out set to 5 W. I'm on 40m. My antenna SWR is about 1.7:1 at 7.00
> and 7.15 MHz and dips smoothly down each way to about 1.2:1 in the middle at about 7.08. However, the number of power
> bars is 5 at each end of the band and 4 in the middle, just opposite of what I would expect given the SWR profile.
> With the DL1 dummy load, it's 5 bars all across the band.
>
> Yes, I read the power output accuracy disclaimer in the manual and I'm not complaining, just curious about this
> behavior. No, I do not have the KAT1 antenna tuner.
>
> Thanks much,
>
> Elwood, WB0OEW, Socorro, NM
>
>
> _______________________________________________
> Elecraft mailing list
> Post to: [hidden email]
> You must be a subscriber to post to the list.
> Subscriber Info (Addr. Change, sub, unsub etc.):
>  http://mailman.qth.net/mailman/listinfo/elecraft   
>
> Help: http://mailman.qth.net/subscribers.htm
> Elecraft web page: http://www.elecraft.com
>
>  

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[Don Wilhelm-4]

Elwood,

The K1 (without the KAT1) uses a diode detector to determine the amount
of RF Voltage at the output (just like using an RF Probe).  The power is
calculated in the microprocessor with the assumption that the load is 50
ohms resistive.

Of course, your antenna is not likely to be 50 ohms resistive, so the
calculation done by the K1 will be in error by the amount your antenna
differs from that ideal 50 ohms.  If your antenna presents an impedance
greater than 50 ohms, the RF voltage will be higher with less power
applied, and your K1 will not develop as much power because it 'thinks'
the power is high enough already.  The converse is true if the input
impedance to your feedline is low (the K1 will actually develop more
power than it indicates).

When the load is 50 ohms pure resistive, the K1 power calculation is
really quite accurate.

73,
Don W3FPR

Elwood C. Downey wrote:

> Hello all,
>
> I've had K1 S/N 2594 on the air for a few months now and having a blast. Great transceiver. Thanks elecraft!
>
> But I'm curious about the power output scale. I have Out set to 5 W. I'm on 40m. My antenna SWR is about 1.7:1 at 7.00
> and 7.15 MHz and dips smoothly down each way to about 1.2:1 in the middle at about 7.08. However, the number of power
> bars is 5 at each end of the band and 4 in the middle, just opposite of what I would expect given the SWR profile.
> With the DL1 dummy load, it's 5 bars all across the band.
>
> Yes, I read the power output accuracy disclaimer in the manual and I'm not complaining, just curious about this
> behavior. No, I do not have the KAT1 antenna tuner.
>  
>

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