[Elecraft] K3 power output problems

[Ian White GM3SEK]

Don Wilhelm wrote:
>
>There is one possibility of a loose connection in the ground path for 
>the antenna connectors.
>
>At the upper right-rear corner of the K3 there is a 2D connector, a 
>long screw and a standoff is fastened to the threads of that long 
>screw. The tightness of that standoff is important to the ground path 
>to the antenna connectors.  See page 22 of the K3 Assembly manual.
>
>To tighten the standoff, you will have to first loosen the screw that 
>goes into the inside end of that standoff, then tighten the standoff 
>with pliers (or better yet, a 3/16 inch wrench).  Once you have 
>tightened the standoff against the 2D connector, you can tighten the 
>screw again.


That slender pillar is the main return path for an ampere or more of RF 
current flowing between the KAT3 board and the rear panel sockets. As 
someone whose design instincts were developed at VHF, where all RF 
ground paths must be short, broad and direct, I didn't feel comfortable 
about that corner of the K3.

Yes, we know that "it works" and "it's good enough for HF". But in these 
days of compulsory EMC testing and microscopically detailed product 
reviews, even HF designers are coming to realise that bending the rules 
for good RF grounding will eat into the margins of performance, spurious 
signal rejection and stability.

RF grounding of the KAT3 board is also far too dependent on the 
tightness of the screws at each end of the pillar and the cleanness of 
all the contact surfaces.

That ground return path can be much improved by connecting the mounting 
screw of J1 directly to the corner of the KAT3 board, using two solder 
tags that are overlapped and soldered directly together. My K3 doesn't 
necessarily work any better, but it does satisfy the instincts of an old 
VHF hound  :-)


-- 

73 from Ian GM3SEK
http://www.ifwtech.co.uk/g3sek