the bias doesnt change, but any PA pushed into its supply rails
generally operates at maximum efficiency .
this is because there is no potential between the supply rail and the
active device.
in undersaturated, quasi linear conditions , there is the additional
dissipation because the supply voltage exceeds the output voltage.
On 19/06/2020 10:02, Al Beard wrote:
*Hi guys,*
*
*
*I've never seen any ham rigs, HF or VHF with the bias changed
depending on modes. Not one.*
*FT620, FT-221, FT897D FT-450, IC-910H and I've looked at the circuits
of many others:*
*FT-200, TS-520, TS-820 and commercials, Codan, Crammond and Racal.*
*
*
*Alan VK2ZIW*
*
*
*On Fri, 19 Jun 2020 08:54:17 +0930, Mark Jessop wrote*
> Heat issues might be the case for 'shack in a box' rigs like
IC-7100s, FT-857s etc...
>
> However, rigs like the IC-7300, IC-7610 will quite happily sit there
putting out 100W of FSK (e.g. FT8) pretty much continuously. It helps
that they have decent cooling. Since I'm feeding in that FSK signal
via an audio input, the amp isn't biased differently...
>
> Can't really speak for Yaesu rigs, as I don't own any.
>
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