This has nothing to do with an earth connection. What you are addressing, and what matters, are SHIELDING and BONDING.
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73, Jim K9YC
On 3/3/2021 12:14 PM, Kent AA6P wrote:
Ground connections inside the transceiver case can also cause problems.
I don't know if this is a possibility with the K3S, but it did occur with the ICOM IC-706MKIIG. Some transceivers after a change in the final output transistors would break into oscillation around 11 MHz. The problem was only seen when using the 15 meter and 17 meter bands and the impedance seen at the antenna connector was a major factor. The problem was often resolved by tightening the screws attaching the various circuit boards to the case and by cleaning a number of spring ground clips. I believe the eventual solution involved additional design changes in the radio.