Hi,
What is the normal operating temperature of a 450b SM antenna with high gain, operating in the frequency range 5.725-5.795MHz ?
Are you asking about what ambient temperature the product can operate in?
This is listed on the spec sheet, and is common to most products within the PMP 450 platform of parts, -40 to +60 C.
Our units 450b sm are on average with a temperature of 52 to +56 C when active, I just think it is a bit high? Or is it normal?
Most of our 450b’s range in temp from 50c to as high as 69c… but mostly average around 55c. Ambient temps range from 25 - 38c.
EDIT: although now I’m suspecting that the temperature being displayed may be inaccurate as I found a 450b with a temp of 73c 
The temperature that the radio reports is a very different thing than the ambient operating temperature.
73C may indeed be correct for the radio reporting that.
To answer the original question, all temps reported in this thread could be considered normal depending on the ambient temperature.