Wendell - W5FL wrote:
> Thanks for the response to my request on wire size for grounding and rebar
> welding and grounding. If anyone still has any input on this previous
> message, looks like I am going to be delayed a few days with freezing weather
> again next week so pouring concrete looks like mid next week or later.
> (Frost line is still about 1 inch for those with real wx)
> Now I am concerned with the three coaxes (RG173/u or Times LMR400), three 8
> wire control cables for rotator and switches, etc. Polyphaser says to ground
> the shields of the coaxes at the base of the tower, but says not to use non
> hard line coax because moisture gets in when you remove the pvc jacket to
> ground the coax shield. They have very little to say about the control lines
> and they should be important, also.
> Question 1: Do I need to do anything to these coax and control lines if they
> are going to go to some form of lightning arrestors about 100 feet away where
> they go into the house? I guess if it is really important to ground the
> shield, I can use a box with feedthroughs and put PL-259 connectors on each
> side with drip loops. I have never had much luck in keeping the moisture out
> of this type of arrangement, though.
YES, ALL COAX LINES SHOULD BE GROUNDED TO THE TOWER AT THE ANTENNA AND
AT THE BASE OF THE TOWER BEFORE THE CABLE GOES INTO THE CONDUIT OR
BEFORE IT GOES INTO A JUNCTION BOX.
YES, USE FEEDTHROUGHS (OR BETTER, A POLYPHASER LIGHTNING ARRESTOR) AND
USE PL-259s ON THE CABLE. THEN WATER PROOF WITH ONE OF SEVERAL METHODS
(WHICH I CAN DESCRIBE IF YOU NEED IT)
> Question 2: Has anyone any suggestions on the least expensive (but good) way
> to protect these coax and control lines where they come into the house? Is
> any protection required at the rotator or switchboxes? I was going to put a
> home weather station about 30 feet up the tower, but will each of these
> additional control lines (14) also require protection at the unit or base of
> tower and going into the house?
THERE ARE SEVERAL QUESTIONS IMBEDDED IN THIS QUESTION #2. FIRST OF ALL,
THERE IS NO GOOD "LEAST EXPENSIVE" SOLUTION. EACH INSTALLATION IS
DIFFERENT. YOU MUST ESTABLISH A SINGLE POINT GROUND, PREFERABLY JUST
OUTSIDE YOU SHACK OUTSIDE WALL. POLYPHASER GOES INTO DETAIL ON THIS IN
THEIR "GROUNDS FOR LIGHTNING PROTECTION" BOOK.
EACH WIRE GOING INTO/OUT OF YOUR SHACK MUST BE PROTECTED, IN SOME WAY,
FROM LIGHTNING. THAT MEANS A DC-BLOCKED UNIT IN SERIES WITH COAX
CABLES, SHIELDS SHORTED TO GROUND AT THE ANTENNAS AND AT THE BASE OF THE
TOWER AND AT THE SINGLE POINT GROUND, AND OTHER LINES (CONTROL LINES)
PARALLEL CONNECTED TO MOVs TO GROUND AT THE BASE OF THE TOWER.
POLYPHASER SELLS THE LATTER TOO.
I HAVE EVERY CONTROL LINE CONNECTED TO A POLYPHASER ANTENNA CONTROL
LIGHTNING PROTECTOR (MOV UNIT) INSIDE THE BOX AT THE BASE OF EACH
TOWER. THE POLYPHASER UNIT HAS EIGHT (8) WIRE CAPABILITY PER UNIT. YOU
MUST VERIFY THAT YOUR OPERATIONAL VOLTAGES (ROTOR CONTROL, RELAY CONTROL
VOLTAGES) DO NOT EXCEED THE THRESHOLD VOLTAGE OF THE MOVs. THE MOV
VOLTAGE CAN BE SPECIFIED TO POLYPHASER FOR UNIQUE APPLICATIONS.
ADDITIONALLY, I HAVE MOVs TO TOWER GROUND AT THE TOP OF THE TOWER FOR
THOSE CONTROL LINES THAT ARE THE UPPER MOST LINES ON THE TOWER. THAT
IS, THE HIGHEST ANTENNAS/ROTORS/RELAYS ON THE TOWER HAVE ANOTHER SET OF
MOVs TO GROUND AT THEIR MOUNTING POINT ON THE TOWER.
READ AND RE-READ THE POLYPHASER BOOK. IT'S COMPLICATED, NOT SIMPLE.
AND ASK MORE QUESTIONS. THERE IS NO SUCH THING AS A DUMB QUESTION ON
> Any and all assistance appreciated. It has been 18 years since I put up my
> last tower in San Diego and the lightning protection field has changed
> considerably from one ground rod at the base of the tower!
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