"W2RAC" wrote in message
...
Some preamp get there power from the coax and the watt meter would dc
ground the coax, therefor no voltage to the preamp.

Also be aware that unless you place the preamp at the antenna you are
unlikely to obtain any system improvement unless the NF of the preamp is
better than the rig's front end NF.
By placing the preamp at the antenna it will overcome/mask the loss in the
coaxial cable and system NF will be determined by the preamp.
Dale W4OP