[Elecraft] Re: k3 SWR readings seem generous

[Stewart Baker]

On Sat, 3 Jan 2009 07:34:13 -0600, Phil & Debbie Salas wrote:
> "I always use 5W, ... when I tune up my external ATU."
>
> Actually, I use 15 watts for tuning both the internal K3 tuner, 
as well as
> my external MFJ-998 tuner.  I do this for two reasons:
>
> 1)  I get much better SWR agreement between 15 watts and full 
power than I
> do with 5 watts and full power, especially on the external 
tuner.
>
> 2)  I figure that using a switching-type tuner stresses the 
10-watt output
> circuitry of the K3 at 5-watts tune power (all that 
hot-switching).  But at
> 15 watts, the K3 100 watt PA should have plenty of margin.
>
> It might be interesting to know what power levels Elecraft 
recommends
> regarding radio stress during tuning.
>
> Phil - AD5X
>
With my setup.
a) I use 5W which gives an accurate VSWR reading on the LP-100A.

b) A power level of  5W keeps the potential QRM level to a 
minimum. Of course radiating no tune up power would be best. 

c) I am sure that the K3 10W PA would stand 5W for a 30 second 
tune.. 

d) I pre-tune my homebrew fully balanced ATU prior to pressing the 
TUNE button. No live RF switching is involved.

Hot switching RF in an external ATU is not to be recommended for 
any radio at any level.

Stewart G3RXQ
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