Originally Posted by pitcoken

If your body changes the level of white noise then it is changing the resonant frequency of the antenna. Verify one more time that it is not shorted. Where did you get your coax? Are you sure it is 50 ohm and not 75 ohm TV coax? Are the connectors properly installed? Has the cable been crushed or crimped in a tight turn? Any of these defects can produce expected results from a multi-meter but cause significant matching problems. Water in the coax is another culprit that is difficult to isolate! The device in the picture is a combination power meter and antenna tuner. It is not obvious from the picture, but read the instructions and make sure the antenna tuner is switched OUT of the circuit while you tune the antenna. With the power meter you can read forward or reverse power. Reverse power results from a poor match - energy that you wish to be radiated is reflected back toward the radio! You tune the antenna to minmize reverse power. If you really want to know the SWR value, after you have tuned the antenna to minimize reflected power, measure both forward and reflected power and use the calculator here http://www.ac6v.com/swrmeter.html. To tune the antenna, you need to adjust its electrical length. Depending upon the antenna this is done with a screw on the base or by physically extendng or retracting the whip. Since this is an AM transmitter, simply keying the microphone will not provide useful power output. Hopefully your radio has a TUNE switch which will transmit a tone at a level that will produce 80 to 100% modulation. If not, then you will have to whistle-up the output power by (guess what) whistling into the microphone. Hope you can whistle long time! Record the reflected power on Channel 19. Then tune to Channel 18 and record that value. If the reflected power on Ch 18 is LOWER than Ch 19 then your antenna is TOO LONG. If the reflected power is HIGHER than Ch 19 then your antena is TOO SHORT. Make adjustments in 1/8 to 1/4 inch increments. If you are unable to resolve any difference in Ch 19 and Ch 18 you may go to a lower channel, but it is possible that you might pass the resonant frequency of the antenna. Ch 19 is at 27.185 Mhz (NOT 162.185 as stated elsewhere.) If you aren't certain, another method is to record the reflected power at each channel from 19 down to 10 or so. If the reflected power drops along the way then then increases again, that indicates that the antenna is resonant at the point at which it dropped. I would suggest that you make friendly with a local amateur radio operator. This is no longer a sure thing (since no-code license was introduced) but he can provide probably help. Good luck!