For operation in mode B (uplink 432.125 – 175 MHz CW/LSB) a low-power transmitter or transverter (approx. 1 – 5W). As antennas, circularly polarized antennas are particularly suitable, but this is not a requirement. The signal itself should be strong enough not to overload the transponder. You can tell by the signal distortion on the downlink.
On the downlink (145, 975-925 MHz CW/USB - watch out for signal inversion) it is necessary to have a gain directional antenna (approx. 10 dB). It will help a lot preamplifier, because without it the signals are only S1-5, which results in many stations adding power to 70cm.
That AO-7 is in B mode can be recognized by the beacon signal at 145.972 MHz. If it is not there, the transponder is in mode A or is disabled.