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1/4 Wave Shorting Stub

The Ultimate in Coaxial Lightning Protection!
 A simple way to protect your transmitter investment is available. 

Antennas are DC grounded yet transmitters continue to get damaged through the coax from lightning strikes. The stub stops the lightning before it can get to your transmitter.        

1/4 wave shorting stub
1/4 wave shorting stub head
1 5/8 Flanged Stub shown as an example.

Stubs can be made in 7/8, 1 5/8, 3 1/8 and now in 4 1/16

For higher power contact Xenirad to discuss your requirements.

Special stubs can be built for harmonic filtering.
Open stubs can be used to remove signals that interfere with 5G or GPS.
STL Shorting Stub
STL stub. 900-1000Mhz

The 1/4 Wave Shorting Stub also referred to as a 1/4 wave shorted stub, connects between your transmitter and your antenna system to short the center conductor to ground providing an unmatched degree of lightning protection for your transmitter. The stub is virtually invisible to your transmitter offering negligible insertion loss, <.02db, and an input VSWR <1.01 with return loss values typically >50db. The stub is tunable which allows for fine antenna matching in the field. The frequency agile stub can be tuned across the band it is made for. EX: FM stub is tunable from 87 to 110 Mhz. Custom frequency requirements are welcomed as well as various connector options, Flanged/Un-flanged, 7/16 DIN, N etc. Stubs can be made in 50 or 75 ohm to fit your requirements.

The Xenirad 1/4 wave shorting stub was designed top to bottom to be a stub. Don't settle for stubs that are fixed frequency and pieced together, these stubs are only cut in 1 MHZ increments and may increase your VSWR.  The Xenirad 1/4 wave shorting stub comes precisely tuned to your frequency and can be retuned to a new frequency if easily if needed. 


Our guarantee: Should your stub ever be damaged by lightning simply return it to Xenirad for free repair or replacement. (Shipping to Xenirad excluded.)

Curly Q stubs (not pictured) are an inexpensive way to protect an exciter from a tube type amplifier. These stubs are not recommended for, or guaranteed for, lightning protection. Contact Xenirad for details.

  • Capable of handling very high discharge currents. 


  • Excellent transmission characteristics.      

  • Maintenance free, no parts to replace after a discharge event.                              

  • Acts as a broadband filter and reduces AM signals by >50db at sites where an AM and FM are co-located. The improvement is FM audio quality is amazing.   


  • Stubs can be made for all power levels and frequency requirements including STL and RPU applications and in a variety of connector options.                                         

  • Excellent protection for both transmitters and receivers.                                              

  • Made in the USA

  • Cheap insurance against lightning damage when considering off air time and repair cost

  • The slot does not radiate RF as it phase cancelled.

stub sweep
Machining a 1/4 wave shorting stub tuning slug.
Machining a 1/4 wave shorting stub tuning slug.

Here is a sweep of frequency agile stub built in 1 5/8 rigid coax tuned for 95.9Mhz. Input VSWR 1.0036 and return loss -54db at center frequency. Insertion loss is lower than the "bullet" used to calibrate the instrument for the measurement. These measurements are typical. 

Available at :

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