Hello operators.This ones got me.Motorola spectra uhf high power radio that does 26 amps on transmit when antenna not connected to radio.But when its connected drops to 15 amp output on transmit.
I'll assume you're not completely daft, and ran your test into a dummy load. The lower current draw when hooked to an antenna could be indicative of a mismatch on the antenna feedline. Or... that could be normal, and the higher current draw could be a result of a mismatch when keyed into a mismatch. Bottom line, a good antenna, and a good dummy load should cause the radio to pull about the same current.
It has an 18 inch RG-58 coax tail that comes out of the radio and connects to antenna coax.Would this thinner diameter tail be restricting output?
No, not in the manner you're thinking. 18" of RG58 is not a lot of loss, and the thinner coax really just means it's power capability is less than a larger coax - but still PLENTY for what a Spectra can put out.
And is there a way to directly connect antenna coax to radio without using tail? Like an adapter of some type.
Yep. Get an adapter of some type. *shrug*
Anyone know why this would be happening? Thanks for your advice.
No. We have no way of knowing. All you're gonna get is guesses, with varying levels of education and experience to back them up. You're gonna have to trouble shoot it yourself. The difference in current draw is telling you that there is a difference in loading on the transmitter. Take it from there.