[SBE] conversation topic: how often do you check tower ground

[Mike Langner]

Years ago at two of the AM stations I used to take care of we had tenants
either in an apartment attached to the transmitter building or in an
apartment immediately adjacent to the transmitter building. In one site
employees got free or close to free rent for watching out for our copper, in
the other we simply rented the modest single family dwelling for a low rate
with the understanding that the tenant had "lookout" duties. In both cases
we had no problems during the times there was a frequent presence on the
property.  Of course, the price of copper was lower in those days.

How crazy is life?  In the case of the single family detached dwelling, upon
a vacancy, the station owner's son announced that he was going to live in
the little house.  His father announced that, "No, he wasn't!" and sent a
crane with a wrecking ball to cave in the roof.  The rest of the house was
removed a month or so later. Copper then began to be removed, too!

That owner was a colorful part of New Mexico broadcasting history.  Some day
someone will write a book.  It'll contain other episodes, like the time he
drove to California, flew back, couldn't find his car in the parking lot,
and reported it stolen.

Or the time he and his wife flew back from New York via O'Hare with their
kids.  Except that from O'Hare they had to take separate flights due to
airline congestion and sold-out planes.  When he and his wife met at the
baggage claim here, she asked where the kids were.  He'd forgotten about
them, and left them in the Chicago airport.

And that's just the beginning!  (But it's more than enough for now!)

So back to copper -- in my opinion, a human presence is the only reasonable
thing that'll work.  You know the saying, if you build a 20 foot fence,
they'll get a 21 foot ladder. . .

Good luck to all!

Mike Langner
Albuquerque, NM
_________________________


-----Original Message-----
From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org]On Behalf Of
dynotherm at earthlink.net
Sent: Saturday, February 16, 2008 1:14 AM
To: sbe member discussion mail list
Subject: Re: [SBE] conversation topic: how often do you check tower
ground


In that case, perhaps you should consider inspection
at 30 minute intervals like the old days of Tx logging.
No, on second thought, even that may not be enough. ;-)

--------------------------
Phil Alexander, CSRE , AMD
Broadcast Engineering Services and Technology
(a Div. of Advanced Parts Corporation)
Ph. (317) 335-2065   FAX (317) 335-9037


-----Original Message-----

>From: Mike Langner <mlangner at swcp.com>

>Sent: Feb 15, 2008 10:11 PM

>To: sbe member discussion mail list <sbe at sbe.org>

>Subject: Re: [SBE] conversation topic: how often do you check tower ground

>

>Please understand that in my case frequently checking the ground system is

>not so much based on chemistry as much as it's based on copper theft!!

>

>Mike Langner

>Albuquerque, NM

>___________________

>

>

>-----Original Message-----

>From: sbe-bounces at sbe.org [mailto:sbe-bounces at sbe.org]On Behalf Of Barry

>Thomas, CPBE CBNT

>Sent: Friday, February 15, 2008 8:00 PM

>To: dynotherm at earthlink.net; Member Discussion List

>Subject: Re: [SBE] conversation topic: how often do you check tower

>ground

>

>

>Items like this is why the SBE list is such a great resource. Thanks for a

>comprehensive treatment, Phil.

>

>

>Sent from my Verizon Wireless BlackBerry

>

>-----Original Message-----

>From: dynotherm at earthlink.net

>

>Date: Fri, 15 Feb 2008 21:33:01 -0500 (GMT-05:00)

>To:barryt at sbe.org, sbe member discussion mail list <sbe at sbe.org>

>Subject: Re: [SBE] conversation topic: how often do you check tower ground

>

>

>While the systems are separate, they have the effect of the soil

>on copper in common, thus, to an extent, the deterioration of

>all buried copper will be somewhat similar.

>

>If the lightning dissipation/mitigation system is combined with

>the RF ground as may frequently be the case at the tower base(s),

>the condition of the gaps and the lower gap connection to the

>common ring tie is generally indicative of damage, however,

>careful examination of the ATU components is also critical in

>this event. Not only can a strike blow capacitors, it can

>reform coils, sometimes in a spectacular way.

>

>The corrosion life of buried copper varies widely as it is

>essentially a function of soil chemistry. I have seen radial

>systems 60 years old where the finish of the wire had only

>evolved from bright copper to heavy brown (CuO) patina. OTOH

>I have a very few systems turning brittle blue in less than

>ten years.

>

>The difference can usually be found by looking at soil pH,

>chloride, nitrate and ammonium content. When a new system

>is put into cropland care should be taken to bring the pH

>into the mildly alkaline range. If the soil has been heavily

>fertilized, a small sample plot of 1/4 to 1/2 acre should

>be ripped, deeply plowed, pH adjusted (generally by liming)

>and analyzed again a little below the burial depth.

>

>If ammonium or chloride radicals remain present in excessive

>amounts, it should be understood that the radial system will

>be a high maintenance item requiring annual inspection. At

>this point it may be wise to consider an alternative site or

>elevated counterpoise.

>

>If the test plot treatment shows an acceptable result the

>entire area should be conditioned in the same way before

>burying copper (or other metals).

>

>However, most sites in inland areas such as unfertilized

>pasture or grazing land or adequately conditioned cropland

>may not require replacement literally for generations.

>

>One clue pointing to possible ground system deterioration is

>an appearance of base current drift with changing soil moisture

>conditions. Another is an apparent long term shift in base

>impedance. In both cases, the ground system is suspect, however

>the tower(s) may be the cause if not well bonded at section

>joints (usually by tack welding). If either of these conditions

>appears, the tower(s) should be checked and bonded if this has

>not been previously done.

>

>If the condition persists, radials can be checked using a

>"sniffer" coil as the external antenna of a FIM. This is

>simply a loop coil of several turns 4 to 6 inches in diameter

>mounted on the end of a broomstick connected with about 6 feet

>of RG-58 and a BNC connector to the FIM's external input.

>Moving the "sniffer" over the ground about 45 degrees out

>from the tower and comparing results over each radial will

>clearly show low induced current in bad radials. One caution

>is that this process can show a false good reading when a radial

>is broken near the tower. If broken radials are found, it is

>wise to check radials by other means such as end to end

>resistance at adjacent outer ends, or with a clamp-on RFA

>such as was described earlier in this thread.

>

>Unless there is traffic over the radial system on unimproved

>roads or paths, or cattle graze the site, it is unnecessary

>to check the radials of a system in good soil more often than

>every five or ten years unless abnormal operation is suspected.

>

>However, if the soil conditions are poor, annual inspections

>should be scheduled. The inspection should be electrical, as above,

>for broken radials, and mechanical for visible signs of corrosion

>by digging up the ends of a few radials selected at random and

>visually observing their condition. Visually, good wire will be

>flexible, not brittle, and brown, not blue-green. Cleaning with

>sandpaper or steel wool should reveal uniform, unpitted, bright

>copper. Pitting, bluish color or brittle conditions are all

>indicators of deterioration or failure, however the system will

>have a degree of function as long as a low resistance metallic

>path remains.

>

>Where cattle graze over a ground system, or where farming or

>other vehicles travel over the system on unimproved paths,

>annual inspection for broken radials in the affected areas

>is essential and consideration to deeper than normal burial

>should be considered.

>

>Ground systems and their performance in transmission systems

>are one of the topics we cover in the Radio Guide AM Transmission

>Seminars.

>

>--------------------------

>Phil Alexander, CSRE , AMD

>Broadcast Engineering Services and Technology

>(a Div. of Advanced Parts Corporation)

>Ph. (317) 335-2065   FAX (317) 335-9037

>

>

>

>-----Original Message-----

>>From: Barry Thomas, CPBE CBNT <barryt at sbe.org>

>>Sent: Feb 14, 2008 2:22 PM

>>To: A9xw at cs.com, Barry Thomas <barryt at sbe.org>, Member Discussion List

><SBE at sbe.org>

>>Subject: Re: [SBE] conversation topic: how often do you check tower

>>ground

>>

>>The two systems would have different characteristics and purposes

>>and therefore different inspection schedules and procedures.

>>

>>For electrical and lightning grounds, they should be inspected after

>>every known electrical event. I used to physically check during

>>weekly transmitter inspections. I've usually not done a more indepth

>>analysis unless there is an increase in storm or electrical damage.

>>

>>For antenna radials. The system performance usually degrades which

>>will initiate inspection but I typically do a full inspection every

>>2-3 years if the antenna system is stable.

>>

>>Sent from my Verizon Wireless BlackBerry

>>

>>-----Original Message-----

>>From: A9xw at cs.com

>>

>>Date: Thu, 14 Feb 2008 13:12:38

>>To:barryt at sbe.org

>>Subject: Re: [SBE] conversation topic: how often do you check

>>tower ground

>>

>>

>>We're discussing ground system life, how often to check,

>>maintenance intervals, etc. Both radial and rods.

>>

>> Henry

>

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