Abstract: An arrangement for forming a radio test loop in a radio unit comprising several radio transmitters and radio receivers wherein each radio transmitter comprises a test signal output, which is adjustable during an operation of testing the radio transmitter, from a high-impedance state to a low-impedance state for outputting a test signal derived from a signal transmitted by the radio transmitter to a frequency converter for conversion to the receiving frequency before looping to the respective radio receiver. To reduce cable-laying required for the test loop, the test signal outputs of all the radio transmitters are connected with spacings of approximately n.lambda./2 to a common combiner cable connected to the input of the frequency converter, where .lambda.=the wave length at the transmitting frequency and n=1, 2, 3, . . . .