Re: Is it possible get a tension on N connector in RX mode for external preampli for vhf / uhf ?
You can make your own Bias Tee. See this link: http://www.hayseed.net/~jpk5lad/K5LAD%20Memories/Vols%2031-35/Memories--Vol33.htm
I would build a Bias Tee in a metal box because of noise pickup, or radiation on a transmitter cable.
There are more links at the bottom of the above web page link.
For a receiver bias tee, a ceramic capacitor would be a good choice. For a transmitter Bias Tee, I would use 3 or 4 ceramic capacitors in parallel to handle the current, and not overheat. A ceramic doorknob for a transmitter cable would be best, if available.