Hello Osmocom CNI folks,

I am getting ready to set up my own GSM network using nanoBTS hardware (currently going through the incredible pain of satisfying all dependencies to get Osmocom CNI software running on Slackware - because no one makes binary packages for Slackware to my knowledge, I have to compile from source), and I found this note in this wiki page:

https://osmocom.org/projects/osmobsc/wiki/NanoBTS_Getting_Started

"Do not power up the device without a TX antenna"

Can someone please educate me (and possibly other wondering souls) *why* one must not power up a nanoBTS with no Tx antenna connected? I understand how it can be a bad idea to actually turn on Tx output with an open antenna connector, as the lack of 50 ohm termination would case Tx energy to reflect back to the PA or whatever internal components this unit has, but it is also my understanding that these units turn on their Tx only after they establish a good link with a BSC, with the BSC then telling the nanoBTS what ARFCN it should transmit on, and at what power level. Therefore, if I am powering up a nanoBTS for the purpose of getting its DHCP to work and doing abisip-find and ipaccess-config steps on it, then during this phase prior to osmo-bsc configuration, the unit's Tx output should be fully off - so what would be the problem with having no Tx antenna?

For context, once I get past initial DHCP etc configuration, before I deploy my nanoBTS on live air, I intend to check its Tx output first: instead of an antenna, connect an RF measuring instrument (I'll use my CMU200 in the non-GSM-specific "generic RF analyzer" mode) to the Tx output port, verify that the frequency it transmits on matches the ARFCN I configure in osmo-bsc, and verify that Tx power control is working - and only then put the real antenna on. But it would be cumbersome to bring the unit into the lab with the CMU200 while I am sorting out DHCP etc, hence I wonder if it would be OK to have nothing at all connected to the Tx port while I work on those preliminary steps.

M~