[Elecraft] TX IMD

[Alan Bloom]

One factor that affects IMD is power supply voltage variation under
load.  The standard PS cable that comes with the K3 drops several tenths
of a volt at max power.  Add that to power supply regulation and
internal voltage drop in the K.

On my unit, the voltage reading on the K3 display goes from 13.5V to
12.4V when I press the key on CW.  (100W, 14 MHz)  I could easily see
that being the limiting factor in transmit IMD performance on SSB.

Al N1AL


On Mon, 2009-01-26 at 10:19, Julian, G4ILO wrote:
> 
> Gregory Fischer wrote:
> > 
> > Not doubting your TX IMD report in PSK.  But I typically see ~-32dB IMD
> > when 
> > checking PSK at 50W. 
> > 
> You are probably right to doubt it. Such a difference made me try a test
> again, on a different band. I got a different set of results. Probably it is
> better to use a dummy load when testing the TX. The IMD Meter is designed to
> be used off-air (hence when TXing into an antenna) but it would appear that
> other factors can affect the readings. This needs further investigation.
> 
> -----
> Julian, G4ILO. K2 #392  K3 #222.
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