Does that mean you do not have an appropriate 50 ohm Dummy Load?
Teh sentence with "Bendix 263" in it is rather cryptic...
Around here a flat antenna on a random simplex frequency is indistinguishable from a dummy load ;-)
The Bendix 263 MicroMatch is a 60s era forward/reflected power meter with 10, 100, and 1000 watt scales.
After "calibration", it agrees with the power out on an Icom 756 Pro and MFJ 993B tuner. Its manual
gives corrections for VHF frequencies. Its main use here is monitoring output power in the .1 to 10 watt
range usually used for WSPR. Handy little device.