[Elecraft] KX1 Q6 question...

[Don Wilhelm]

Dave,

I don't know the exact serial number, but the change has been quite 
recent.  I can state with certainty that the 2SC5739 shipped with KX1 SN 
2059.
The motivation for the change was to use an RoHS compliant part.
Extra benefit is derived by having the plastic tab (note that the 
shoulder washer should not be used, but it is still being packed with 
the kit).
The 2SC5739 does seem to have higher gain at higher frequencies than the 
2SC2166, so your 20 meter output may improve if you change it, but I can 
offer no guarantees on that, the two devices are quite similar.

Should you make the change and find your power output is above 4 watts, 
reduce the setting of R1 to the 4 watt level.  The components in the KX1 
PA output stage can be stressed at power levels much in excess of 4 watts.

73,
Don W3FPR

Dave G. wrote:
> Can anyone help on the following...
> At what serial number did the PA (Q6) change from a 2SC2166 to a 
> 2SC5739??
> Was there any other reason than getting away from the metal tab??
> Better performance?? Or....????
>
> TIA
>
> --
> Dave G.   KK7SS
> '65 MK III Sprite in Richland, WA
>
> The Original Point and Click  --- Smith and Wesson....
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