[SBE] AM Seminar

[Kent Winrich]

Radio-Guides AM Transmission seminar (it is a great one BTW went this last
September!) is usually held in conjunction with NAB Radio which this year is
in Austin, TX in September http://www.nabradioshow.com/.

Kent Winrich, K9EZ
BroadcastPro.Biz
Raleigh, NC
BAE Systems
Ft Bragg, NC


On Feb 18, 2008 5:01 PM, Barry Thomas <barryt at barryt.org> wrote:


> I'm not aware of one.  You might want to check the RadioGuide web site to

> be sure.

>

> The NAB is holding an AM Directional Antenna seminar at their headquarters

> in Washington, DC March 6-7.

>

>

> http://www.nab.org/AM/Template.cfm?Section=NAB_AM_Directional_Antenna_Seminar1&Template=/TaggedPage/TaggedPageDisplay.cfm&TPLID=72&ContentID=11556

>

> Barry Thomas, CPBE CBNT

> Atlanta, GA

> barryt at sbe.org

>

>

>

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

> From: Ron Baker <ronbaker.ron at gmail.com>

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

> Sent: Sunday, February 17, 2008 12:06:45 AM

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

>

> When is the Radio Guide AM Transmission Seminar scheduled for the west

> coast?

>

>

> On 2/15/08, Barry Thomas, CPBE CBNT <barryt at sbe.org> wrote:

> 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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