HB9TMC

You could check the other voltages:

http://kiwisdr.com/ks/troubleshooting.pdf

This is almost certainly RFI from an unstable oscillator, probably harmonic from a switching power supply.

@f6bir
The default gateway could be missing or wrong defined.
Can you show the output of "ifconfig" and "route"?

@W9SPY
You could try using another power supply at the router (maybe the one from the old router). Just make sure it has the same voltage and polarity and an appropriate amperage rating.

Using a _non_ shielded ethernet cable may also help. (The BBG ethernet shield is connected to antenna ground. And some routers ethernet shields are connected to their PSUs minus pin)

I made good experience with the filament LEDs which recently popped up. They run on such high voltage that they often don't require a switching mode power supply, but only a capacitor dropper and a rectifier.