Is it safe to put RF cable in-between 150W 30db Attenuator and DUT output?

Hi forumers, I have an upconverter module rated 60W with gain of ~40dBm. I am currently connecting the 30dB 150W attenuator directly to the output port (N-type). I am planning to put the attenuator inside a testbox, so I will be using a test cable to connect the DUT. Is it safe to do so? Thanks for your thoughts on this. regards

The power handling of coax is limited by two mechanisms:
* Dielectric breakdown, and
* Losses (which are usually dominated by the dielectric).

At 60W you'll be a long way away from the several-kV breakdown voltages of common dielectrics, so you're OK on that front.
You didn't mention the frequency of operation, but even bog-standard RG58 (see, for example: datasheet.octopart.com/7806A-010500-Belden-datasheet-16156.pdf) will be fine in your application up to 5GHz+. If you use a thicker, better grade of coax then you've certainly got nothing to worry about :)

Don't forget to account for the interconnecting cable loss if you're measuring the output power of the DUT!

Thanks thylacine1975 for the useful info! yes i have already accounted the losses on both input and output interconnects. Freq is C-band and other units @ 80W. regards :)