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3 Minute Shut-down rule

R

rrlane

In today's world of diminishing engineers how can we actually do what this rule requires?
The rule is
"§ 73.62 Directional antenna system operation and tolerances.
(a) Each AM station operating a directional antenna must maintain the relative amplitudes of the antenna currents, as indicated by the antenna monitor, within 5% of the values specified on the instrument of authorization. Directional antenna relative phases must be maintained within 3 degrees of the values specified on the instrument of authorization.

(b) In the event of a failure of system components, improper pattern switching or any other event that results in operation substantially at variance from the radiation pattern specified in the instrument of authorization for the pertinent time of day, operation must be terminated within three minutes unless power can be reduced sufficiently to eliminate any excessive radiation. See § 73.1350(e)."

What is "substantially at variance"?

The rest of it is not any easier.
"(1) The licensee shall measure and log every monitoring point at least once for each mode of directional operation. Subsequent variations in operating parameters will require the remeasuring and logging of every monitoring point to assure that the authorized monitoring point limits are not being exceeded. The licensee will be permitted 24 hours to accomplish these actions; provided that, the date and time of the failure to maintain proper operating parameters have been recorded in the station log."

And so on.
I'm not saying the intent of the rule is wrong but the steps required when something goes wrong may be overwhelming. Ice on towers, snow, lots of rain all can trigger this rule.

How does one do "unattended" operation and comply here?
 
I've wondered about that, too.

Back in the mid 70's, I worked at a station next to the Chesapeake Bay. We had a period of deep-freeze weather, and our 4-tower DA readings were all out of whack.
I called the Chief Engineer, who said all I needed to do was just make a log entry, saying that the weather was causing problems, and that would cover us.
I've always wondered if he was right.
 
If a phase angle or ratio is out, presumably you will reduce power to compensate rather than go off the air. Automatic adjustment would be recommended for this rule.
 
rriane, you did not post the entire text of 73.62 which clearly defines "substantially at variance". 73.62 (b) (1) reads:

1) Any variation of operating parameters by more than ±15 percent sample current ratio or ±10 degrees in phase, any monitor point that exceeds 125 percent of the licensed limit, or any operation at variance that results in complaints of interference shall be considered operation substantially at variance from the license and will require immediate corrective action.

You also left out the complete text of 73.62 (c) which is:

(c) In the event of minor variations of directional antenna operating parameters from the tolerances specified in paragraph (a) of this section, the following procedures will apply:

(1) The licensee shall measure and log every monitoring point at least once for each mode of directional operation. Subsequent variations in operating parameters will require the remeasuring and logging of every monitoring point to assure that the authorized monitoring point limits are not being exceeded. The licensee will be permitted 24 hours to accomplish these actions; provided that, the date and time of the failure to maintain proper operating parameters have been recorded in the station log.
(2) Provided each monitoring point is within its specified limit, operation may continue for a period up to 30 days before a request for Special Temporary Authority (STA) must be filed, pursuant to paragraph (c)(4) of this section, to operate with parameters at variance from the provisions of paragraph (a) of this section.
(3) If any monitoring point exceeds its specified limit, the licensee must either terminate operation within three hours or reduce power in accordance with the applicable provisions of § 73.1350(d), in order to eliminate any possibility of interference or excessive radiation in any direction.
(4) If operation pursuant to paragraph (c)(3) of this section is necessary, or before the 30-day period specified in paragraph (c)(2) of this § expires, the licensee must request a Special Temporary Authority (STA) in accordance with section 73.1635 to continue operation with parameters at variance and/or with reduced power along with a statement certifying that all monitoring points will be continuously maintained within their specified limits.
(d) In any other situation in which it might reasonably be anticipated that the operating parameters might vary out of tolerance (such as planned array repairs or adjustment and proofing procedures), the licensee shall, before such activity is undertaken, obtain a Special Temporary Authority (STA) in accordance with § 73.1635 in order to operate with parameters at variance and/or with reduced power as required to maintain all monitoring points within their specified limits.

Basically it boils down to reducing power to put the monitor points within limits. If the variation is more than 5% but less than 15% ratio and/or more than 3 degrees but less than 10 degrees in phase and/or you find a monitor point over by less than 125%, you can continue to operate for 30 days without an STA provided you measure the monitor points within 24 hours and reduce power to put the monitor points within limits (logging it all, of course). If you have a situation with varance outside the 15% ratio, 10 deg phase or 125% monitor point, you need to reduce power to eliminate "excess radiation". That means knowing or measuring what it will take to not exceed the normal radiation of the DA mode in any direction then reducing power to that amount within three minutes or terminating operation (go off the air). All directional stations have a way to operate non-directional. Many times this can be done remotely so I will want to know what power the non-D operation can have and not exceed the radiation limits of the DA.

Modern remote controls can have two sets of limits for the DA mode and take proper action if one (minor) or both (substantial variance) limits are exceeded.

Bob
 
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