DC BLOCK

The Tactical Radio, DC Block Lightening Shield, is designed for up to 5KW pep power, and 1-500 MHz frequency range. Applications for the DC Block Lightening Shield, include ground loop elimination, and other situations where undesired DC current(s) need to be prevented from flowing between different sections of an RF system and lightning protection. 

Some Bandpass filters, and Baluns are at DC ground, and using a Bias-T device, requires a DC-Block.

Because of their inherent high breakdown potential, DC-Blocks are ideal for applications where high voltage, DC or AC up to 20 KHz, must be rejected from the RF signal path. Leakage from modulating signals can occur via AC power lines, through ground loops, or poorly grounded coaxial cables; these leakages can impair signal reception. 

The DC-Block can be thought of as a high-pass filter allowing only the RF frequencies to pass through. 

Tactical Radio Gear, DC Block lightening shields, Inner DC Block; are designed with three parallel, 1KV  capacitor(s) placed in series with the center conductor; to prevent the flow of DC and curtail the flow of low-frequency currents, while providing minimum impedance to RF signals. These high voltage chip designs exhibit low ESRs at high frequencies. (0.354Ω @ 1.5MHz, 0.177Ω @ 30MHz and .00354Ω @ 150MHz).
 

With a DC Blocked lightning shield, slow voltage build-up from wind, rain, snow or airborne debris, will not get to your radio. The Shield provides overvoltage fault protection against damage caused by high energy surges due to impulse sparkover response. Under normal operation when the GDT reaches the turn-on threshold it will go into a transitory soft turn-on, as the gas just ionizes, and bleeds the static charge to ground. No noise is generated since it never gets to the arc phase. 

These devices do not influence the signal; however, in the event of an overvoltage surge, such as a lightning strike, the GDT switches to a low impedance state and diverts the energy away from the antenna. Littelfuse's highly reliable CG/CG2 Series GDTs provide a high degree of surge protection in a small size ideal for board level circuit protection. GDTs function as switches which dissipate a minimum amount of energy and therefore handle currents that far surpass other types of transient voltage protection. Their gas-filled, rugged ceramic metal construction makes them well suited to adverse environments. The CG2 Series (145V-1000V) is ideal for protecting equipment where higher voltage limits and holdover voltages are necessary.

 

The shields are available in two mounting styles:  "Flange Mount" which attaches to a grounding bar, and inline installations’. Available in a wide range of connectors and come standard with the S0-239 UHF type.

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