Transmit current and SWR?

[Spy]

Hello,
Recently i bought few RFM98s. When i connect it through a multimeter i observed that current draw changes depending on what's nearby and antenna length. For example, with my antenna, current is 0.43A, when i put my hand close to the antenna it can go down to 0.4A, and when the antenna is near other metal objects it can go jump up to 0.7A. Can it be used to tune the antenna? The lower is better? BTW, datasheet says that transmit current is .65 to .7A, but i think it's for 6V, my rfm is currently running at 5.1V.

Also are all transmitters really that ineffecient? According to the datasheet: 0.65A*6V=3.9W just to transmit 1W=2.9W into heat? I'll need to put a heatsink on it.

[Felix]

No, a current meter, your hand, and other objects around are not antenna measurement instruments
You need a real instrument like VNA or antenna analyzer to tune your antenna.

Also are all transmitters really that ineffecient? According to the datasheet: 0.65A*6V=3.9W just to transmit 1W=2.9W into heat? I'll need to put a heatsink on it.

A badly matched transmitter/antenna is, yes. In the real physical world there are always inefficiencies. By following good practices you can reduce those to a minimum.
If you have a bad match, most your output power can turn into heat, and even burn your transmitter, no kidding. It's like plugging a shotgun barrel before you fire.