Before you remount K3 remove the audio switching path from it. Many get
feedback from that path. Also it can be inserted form the bottom.
Also the big issue is all the spaghetti traces. The LPF are good as is, just
the switching is a fail and its all layout. Too many intereleaved lines. The real
trouble maker is that all RF in to the filter and out from the filter go by was
In the drawing 3.jpeg The red is new wires yellow are bad wires.
This was built with relays on bottom and works well for 80 through 17m.
KT3 switches antenna to filter outptu or through coax direct to KT1 pin12.
Coax is under board.
In drawing 1jpg The enclosed in red are the troublesome areas.
Yellow bad, green is audio mod, black means cut!, blue is the spaghetti to be removed/altered
That parallel DC lead (tx relay power) is parallel to RF line from KT3... If it looks like a
directional coupler it works like one. Its why there is a ton of RF on the switched
DC+ line during TX. Very bad!
If you don't care for above 17M the fix is messy but easy once the
relays are out. Use one relay per band from 80/40/20 and it works.
RF goes in via KT1 and out via KT3. Also modify the relays power
path to avoid that parallel line.