What must Directional Station Remote Monitor?

AM Radio discussion. Directional arrays are FUN!
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Fran3
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What must Directional Station Remote Monitor?

Post by Fran3 » Tue Apr 05, 2016 3:56 pm

For a 3 tower directional... 2 towers day and 3 towers night... what must you be able to remote monitor?

1 - Tx Final Amp Voltage
2 - Tx Final Amp Current
3 - Common Point Antenna Current
4 - Silence Sensor

and what else?

Must you be able to monitor...
a - phase relationships and
b - antenna base currents?

or can checking these manually each day be enough?

and someone said we must monitor ratio's... I'm not sure if this ratio's of phase or of antenna base currents... or not at all as someone else said.

Thanks for any help.

ChuckG
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Re: What must Directional Station Remote Monitor?

Post by ChuckG » Tue Apr 05, 2016 6:41 pm

Not required to monitor anything specific. You are required to remain in compliance with terms of your license, and correct variances or shut down within specific time periods. Exactly how you accomplish that is up to you.

I have my remote controls set up to monitor common point current, ratios and phases. If any stray out of limits I get a phone call. If I can't correct it in time I can reduce power or shut down as necessary.
Often as not there is nobody in the studios when power change times roll around in the summer, so we consider the operations to be "unattended".
I do have a paper log and we do log DA and ND readings to it periodically, mostly just to have a record things were in compliance if anyone asks. They aren't logged frequently enough to meet the rules dealing with parameters at variance, thus the automatic checks.
That's met favor with every FCC inspector who's wandered by thus far.

"ratios" are the current ratios of each tower Vs the reference tower. Normally the reference tower is set to 1.0 and the others compared to that.
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Chuck Gennaro
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Deep Thought
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Re: What must Directional Station Remote Monitor?

Post by Deep Thought » Tue Apr 05, 2016 7:39 pm

Common point is required on the remote control since that is what is used to determine whether the station is operating withing tolerances.

Tower loop current ratio and phase is also required but doesn't necessarily have to be immediately available. However, you are required to remedy a serious out of tolerance situation within 3 minutes.
§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).

(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.
The reader is tasked with how you will accomplish that without having the antenna monitor hooked up to the remote control and checking parameters at each pattern change.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

ChuckG
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Re: What must Directional Station Remote Monitor?

Post by ChuckG » Tue Apr 05, 2016 9:11 pm

Deep Thought wrote: (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).
That's the section that makes traditional logging appear insufficient.

Suppose station personnel check and log parameters at pattern change and at three-hour intervals thereafter.
15 minutes after pattern change a capacitor fails (true story!), putting the station severely out of tolerance. "Failure of system components".
You won't be reacting within the required three minutes. You'll miss it by 2 hours and 42 minutes at best. If readings are only checked at pattern changes, a day may pass.
I've always wondered how stations who log at 2-3-4 hour intervals answer the question "how will you react within 3 minutes" if asked. The answer is "we cannot", no?
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Re: What must Directional Station Remote Monitor?

Post by Deep Thought » Tue Apr 05, 2016 10:19 pm

Yeah, this is one of the inconsistencies in the rules. However, there it is. The good part is if something happens that drives the parameters that far out it usually also disturbs the common point load enough that the transmitter complains.

Modern remote control systems can poll the antenna monitor often enough to detect this and set an alarm but I see less than half of them even connected to the remote. If I were an inspector wanting to make trouble for a station with parameters out of tolerance, this is one of the places I'd start.
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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