K3 transverter output question

[W8ZN]

Not sure if this is a question or observation. Saturday I was setting up a DEM transverter to be used with a K3 and found the low level output of the K3 is dependant upon the input attenuator setting on the DEM transverter. I set the max output on the K3 in the menu to 1.8 dbm, which the rig displayed. When the DEM was adjusted for max attenuation, the K3 showed 1.8 dbm but when I turned the attenuation pot on the DEM transverter to decrease the attenuation and get more output, the output of the K3 dropped to .7 dbm as noted on the K3 readout. A assume this is because the 10m input of the DEM is not 50 ohms but it just surprised me after dealing with many other rigs. I guess even the low level output is ALC controlled which would probably explain it.

 

Terry - W8ZN

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[Steve Kavanagh]

Terry:

I have seen much the same thing with a DEM transverter and my K2, and I agree with your assessment.  The IF circuitry in the DEM transverters does not seem to be designed to give anything close to a 50 ohm input impedance, especially when set for for very low input powers.  It is quite reactive, at least for my transverter.  I ended up adding a component or two inside the DEM transverter to improve the matching, so the K2 could drive it properly.

73,
Steve VE3SMA


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