Swinging SWR

[garbagebag]

My swr is at a 1.5 , but swings into 3- 3.5 area, with modulation. Is this a sign of a bad ground? what could cause this.

['Doc]

No, it isn't a sign of anything, except maybe forgetting to change that meter to the watt meter mode. SWR isn't power dependent, it stays the same no matter what power is used. What changes is the calibration of the SWR meter with power changes. That means that the SWR meter isn't reading anything accurately when you 'modulate'. To find what the SWR is, use just the carrier, no modulation at all. That's when you calibrate the meter -and- when you do that checking. After you see what the SWR is, just change the meter to read power.
- 'Doc

[Red Warrior]

SWR is a ratio of transmitted signal to reflected signal. When first keyed, most meters self calibrate on the output. Manual meters require that you key up and set the meter to a calibration point based on the steady state transmit signal. The key words here are "steady state". If the signal is moving (as in being modulated) the meter cannot keep up and the SWR indication is meaningless. Follow the instructions. Always check SWR with deadkey (no modulation).