The advantage to cross-needle meters is that they provide three pieces of data in one reading.
In the case of a cross-needle power/SWR meter, you can read:
1. Forward power -- this is the RF power being delivered by your transmitter to the antenna system. Set the scale switch to the lowest setting that will result in the highest non-pegged reading on the meter. If your meter has a 20W/200W scale switch and your transmitter is putting out 10 watts, use the 20W scale--it it's putting out 30 watts, use the 200W scale. If you are transmitting in SSB mode, use the PEP setting. For all other modes (FM, AM, CW, etc.), use the AVG setting.
2. Reflected power -- this is the RF power being reflected back to your transmitter due to a lack of resonance in your antenna system at that frequency.
3. SWR -- The Standing Wave Ratio is a mathmatical function of the forward and reflected power. The meter designer has done the math for you by putting an SWR scale on the meter. These are the curved lines that are drawn on the meter face, usually in a different color, between the forward and reflected power scales. Find the point where your forward and reflected power meter needles cross. Look past that crossing point to the SWR scale on the meter face. If you are lucky, the crossing point will be directly above an SWR scale line. Follow that line to the SWR numbers to get your SWR reading. More often, that crossing point will not be directly above an SWR line so you have to figure out which SWR lines your crossing point is between and then interpolate between those two values.
