1 RF Lightning Arrestors & Grounding Mike Baker, W8CM

2 The Answer: “it depends”

3 Now, what was the question?

4 “THE QUESTION” What’s the right lightning arrestor to use ? Where should I place it ? Do I need to ground it ? OK, OK, so maybe that was 3 questions Or…..maybe it was a question in three parts

5 These questions are “Guru level” Answers: ASK GURU RF

6 Can we “arrest” lightning?

7 Or, do we really just protect from it?

8 The Bottom Line: Many different “expert” opinions No guarantees Nothing is foolproof Direct Strikes do damage Real Problem: induced energy from close strikes BUT We can improve the odds Commercial communications sites take hits and keep on working Your site can too

9 WHAT’S THE RIGHT ONE TO USE ?

10 SPARK GAP Cushcraft Blitz-Bug, Hy-Gain, etc. Cheap, poor protection, for older tube gear Divides energy Specifications “loose” Passes DC

11 ¼ wave SHORTED STUB Practical mostly for higher frequencies Bandwidth dependent Divides energy Easy to build DC shorted

12 GAS TUBE Wideband, shunting Precise specifications DC pass

13 GAS TUBE TYPICAL SPECIFICATIONS Impedance “off” > 10,000 Meg Ohms Impedance “on” a few milliOhms Switch time less than 100 nanoseconds When “on”, voltage is less than 30 volts Surge current 5000 Amps (IEEE 8/20 uS pulse) Life > Amp pulse

14 SHUNT TYPE R C RFCRFC Blocks DC Frequency Dependent “Bleeds” static Power Ranges

15 MODIFIED SHUNT TYPE R C RFCRFC Pass DC around or insert it Numerous models Frequency Dependent $ $ $ BLOCK RF, PASS DC

16 PolyPhaser: the “Coca-Cola” of lightning arrestors Many models for various power levels, frequency ranges, etc. Generally expensive Highly favor blocking designs

17 Gas Tube Arrestors Alpha Delta Huber – Suhner Etc., etc. Favored by LMDS (etc) industry for dc pass to equipment on roof/tower top Wideband (dc- 3 GHz, for example) Reasonable price ($30-$60)

18 I.C.E. Model I348 Rotator Line Suppressor/RF Filter Use this Suppressor on 4, 5, 6, & 8 wire rotator and remote relay lines Unshielded control line conductors used to operate antenna rotators, remote switches, weather sensors, and so on are easily charged to thousands of volts above ground by overhead lightning discharges which can destroy equipment. In RF transmissions, these same control lines often couple RF and re-radiate signals causing RF interference to other devices. This Line Surge Suppressor/Filter from ICE solve both problems in one convenient unit. Easy to install, this filter shunts RF currents and AC/DC voltages above 50 directly to ground. Uses metal oxide varistor devices and ceramic RF bypassing circuitry.

19 Grounding ? Ask the other Guru (ground rod)

20 Well, OK: just a few comments on grounding Bond the coax to the tower at the top, plus the bottom and even in-between (if a long cable) Protect all rotor and switch control lines also Use heavy wire (2 gauge) for DC Use low inductance strap for RF Cad Weld connections vs. clamp Use entry ground window (heavy bus bar) Bond all equipment in equipment room

21 radio lightning arrestor ground block Wrapping It All Together: Sample Installation.. * *...

22 The End 73

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