[VHFcontesting] DEM/KK7B xvtr spurs

[MICHAEL SAPP]

Hi: My favorite spur-killing trick is to put a 1/8w high ohm resistor (100K+) with one lead cut off and  the other lead cut short to form an L-shaped contact. Take a 3 inch piece of heat shrink and shrink it over the resistor body.  Move this "tool" around on the filter traces and strip lines while watching the DUT output on the spectrum analyzer. Anywhere the resistor attenuates a spur, mark that point on the trace and solder one L-lead of a similar resistor (with its other lead cut off) on the filter or strip line trace standing upright. Moving the soldered resistor at various angles from vertical may also change the capacitance effect and further attenuate the spur. This works especially well on LO multiplier stages and one can make a vast improvement over the stock DEM/KK7B LO output quality, especially the earlier design versions. The DUT output should also improve in  a manner somewhat proportional to the amount of spur energy which the resistor dampens. This trick will not cure bad grounds or other mis-behaving active or passive components, but you may be surprised how often it can clean up these popular transverters.  Mike WA3TTS