[Elecraft] TX IMD

[d.cutter at ntlworld.com]

Is there a "sweet spot" to which one can adjust the power output for minimum IMD, if so, how would you do it easily?  I presume you would need another rx or spectrum analyser.  And I bet it changes with antenna reflections, ie from one end of the band to the other. 

I dare say a lot of K3s are followed by linears which add even more IMD, so, it might be tricky to optimise for the station as a whole and not just at minimum drive from the K3; perhaps a power pad is needed, but who would bother ?

It is hoped that the Elecraft linear might take this into account.

David
G3UNA

---- Geoffrey Mackenzie-Kennedy <gm4esd at btinternet.com> wrote: 
> Jan Erik Holm wrote on Monday, January 26, 2009 8:52 AM
> 
> As you say, it´s getting rare these days with radios in the
> -30 to -40 dB bracket. And we are just going to be content
> with it? No not IMO.
> 
> Jan,
> 
> I agree in the context of Amateur Service radios.
> 
> The time might come perhaps sooner than later when it does not matter 
> whether or not we amateurs are content to put up with poor Tx IMD 
> performance, somebody else might set the limits for us if we do not. 
> Although the Amateur Service has been allowed for decades to police itself, 
> there is growing pressure from some users who have been assigned allocations 
> adjacent to our bands to clean up what could be called "outside band edge 
> whiskers" created by amateurs, be they key clicks or IMD products or other 
> types of garbage.
> 
> Forty years ago in Canada the Type Approval specs for low power HF 
> transmitters for use in commercial services set the limit for Tx IMD at 30db 
> below each tone in a two tone test at full rated PEP output. Input to mic 
> connector, also to any other audio input interface. I must own up to being 
> involved in writing those specs. However today such a limit does not reflect 
> what is required by responsible spectrum management nor does it reflect what 
> can be ahcieved in practice at reasonable cost. We need to look for much 
> better performance than 30db below test tone.
> 
> FWIW
> 
> 73,
> Geoff
> GM4ESD
>