No single topology suits every installation; choose by RF bandwidth, DC continuity, maximum line voltage, residual protection target, power, PIM and service strategy. Gas-discharge-tube protectors are broadband and may pass DC, but their static and impulse sparkover, follow-current behavior, cartridge life and residual energy require coordination with the equipment port. Quarter-wave or shorting-stub designs can offer low residual voltage in a defined RF band, but bandwidth and DC behavior depend on the mechanical filter. Hybrid stages add finer clamping at the cost of more topology-specific limits. Compare nominal discharge current only when the waveform is identical: an 8/20 microsecond induced-surge rating is not interchangeable with a 10/350 microsecond partial-lightning-current rating. Also compare impulse sparkover, residual voltage, RF power, VSWR, insertion loss, PIM, environmental seal and replaceability.
A replaceable GDT is useful when broad bandwidth and DC continuity are required, provided sparkover, follow current, residual pulse and cartridge service fit the protected port. Quarter-wave or shorting-stub structures can provide a low residual path in a bounded RF band, but their filter geometry determines bandwidth and DC behavior.
Hybrid protection can add a finer downstream clamp, yet every added stage changes RF loss, match, power, PIM and coordination. Reject any topology offered without a frequency response, line-voltage boundary, named impulse waveform, earth-path requirement and post-event service procedure.