[Elecraft] K2/HF Packer Amp incompatability?

[Geoffrey Mackenzie-Kennedy]

Don,

Shortly after I sent my comment earlier today I received an email telling me 
that the HF Packer amp was intended to be used for CW (Class C?) not SSB, 
and that a modification was necessary for its use as a linear amplifier for 
SSB - presumably at least a change in the amplifier's standing current by 
changing its bias.

However Pat said that the K2/ HF Packer signal was distorted whereas the 
IC-703/ HF Packer signal was not distorted. This suggests that the HF Packer 
amplifer he tested is biased for linear operation, and is not running in 
Class C.

Nevertheless as you suggest the results of a gain vs drive level test would 
remove any uncertainty.

73,
Geoff
GM4ESD


Don Wilhelm wrote on Tuesday, September 14, 2010 3:48 PM


>  That sounds like the amp is not running linear.  First make sure the
> bias is set correctly.
> Then do a test in CW mode -
> Put a small amount of drive to the amp (measure it), and measure the
> output.  Compute the gain.
> Increase the drive by a small amount, and again compute the gain.
> Continue in small steps until you have reached the maximum output of the
> amp.
> The gain should be the same if the amplifier is really linear.
>
> If the input impedance of the amplifier is changing with drive level,
> that can be cured with an attenuator at the input - the driver will then
> see a more constant impedance.
>
> 73,
> Don W3FPR