Lost transmission output half-way through WSJX xmit

[WA1DX]

Hi-when xmitting FT8 by WSJX and using VOX, rig shows "T" but when monitoring signal, it dies after about 5 sec. Powered from computer or 9V battery. Will rig cut out if SWR high after few seconds? Not sure of SWR because tuning loop antenna by ear. Or, is there another problem?

[KG7YSX]

Is your SWR confirmed high?

If your SWR is not high, I would suspect RF. I've had this happen with other rigs, and it was remedied through RF mitigation.