Based on the general ideas of an all-pass network

the condition of forming an allpass network is discussed. The practical circuits of the electron tube all-pass network

and those of the pulse compression filter which is synthesized by the network mentioned above

as well as the experimental results of the expansion and compression are introduced. The experiments prove that it is possible to synthesize a pulse compression filter by using the electron tube all-pass networks. Having used an appropriate compensation technique

the centre frequency of the filter can reach several tens MC

and the corresponding bandwidth can reach 10～20 MC around.