I looked on routerboard.com and on mikrotik.com without success.

Give a look on the upper right of this page (entire page), you will see a picture of the R52 mPCI card.
Click on it, you will be redirected to the shop section. You will see a "Description" button on the bottom of R52 (and R52H) section. Click on it and you will get the tech spec on PDF format.

Bye

I just clicked "Description" as suggested under the R52H and get
"Error 404: Not Found"

The target url is http://www.mikrotik.com/pdf/R52H.pdf

Bad link, perhaps?

The link for .../R52.pdf works fine.

Try the following:
R52
R52H

Thanks for your reply .

This document warns that the amplifier could be damaged if no antenna is connected. What is a safe TX power to use while testing on the bench? Its not always easy to attach antennas when you are just configuring the boards.

I assume if the card is disabled there is no risk to the amp circuits?

Hy, the problem is the impedance which the amplifier seen.
If you want to test it on lab, attach it a little omni antenna (2dBi), or buy a dummy load at 50ohm.

When the card is disable, it transmit nothing, so no problem for the enclosed amp.