Power out levels different between two antennas.

[Dusty1USA]

I have two antennas, a 2016 Sirio ground plane and a Sirio 3 element yagi.
When I am using the gp my power meter out of a 500 watt linear shows a pep on ssb of 300 with an initial swing up to 400 watts then dropping back to around 300 as I continue talking. Then on the 3 element yagi it shows 480 watts pep and only drops back to about 450 watts.
Wondering why it's different for each antenna. Both have a below 1:1 swr.
Putting the meter on RF setting and modulating on ssb the needle barely moves.
?????

 

[DXman]

You probably have different lengths of coax and maybe different brands that might cause the difference.

My /-/-/-/-/ beam has always showed a few watts less than my GP, but I have different brands of feedline and different length also.

There can also be other things that can be involved to show the difference........

 

[sp5it]

Measuring power on antenna always give wrong readings.
That's why we have dummy loads.

 

[Dusty1USA]

Thanks for the replies. Guess I need to get a dummy load.
That would mean I have two dummies.........it and me.