Tektronix 1502 TDR - why this particular physical construction?

[tggzzz]

The "business end" of the Tek 1502 sampler is rather interesting, but why did Tek choose this very elongated layout?
https://www.eevblog.com/forum/rf-microwave/tdr-for-measuring-cablesconnectors-what-is-it-worth-to-radio-hams/?action=dlattach;attach=251890;image
Why not just have the tunnel diode (TD) transmitter and sampling diodes (SD) receiver close together?

Reasons I can think of include to minimise crosstalk between the "transmitter" and "receiver", or because fitting the related components into the case required a separation between the TD and SD. neither of those explanations is satisfying; is there a more fundamental benefit from having the long stripline?

(FFI on the Tek 1502's performance, see https://www.eevblog.com/forum/rf-microwave/tdr-for-measuring-cablesconnectors-what-is-it-worth-to-radio-hams/msg1014762/#msg1014762 )

[David Hess]

One reason not to place them closely together is to prevent the kickout from the sampling strobe from prematurely triggering the tunnel diode as the trigger pulse arrives.  When using tunnel diode pulse generators in sampling applications, it is sometimes necessary to add an external delay line to the tunnel diode pulse generator because of this.