Equipment Performance Measurements

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kcbooboo
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Equipment Performance Measurements

Post by kcbooboo » Sun Sep 15, 2019 1:08 pm

It's that time of year again.

One of the stations I do spectrums for, is running on their backup TX because the main has one PA module out for repair. Does it matter if I take spectrums while they're on the backup TX as long as I document the conditions that existed at the time, or should I wait for the main to be back at full strength?

Also, the main has IBOC and they run that all the time, but there's no IBOC on the backup TX. I wouldn't be able to do IBOC spectrums if they're on the backup TX. They normally run on the main all year but occasionally run on the backup (maybe one day a month on weekends) just to make sure it will work when needed. I can wait a few weeks and hope the main is back to normal but does it really matter per the regulations?

Another station I've done EPMs for apparently found someone else or has decided not to do EPMs because they can't afford them. I suppose they wouldn't be able to afford the fines if they ever got inspected either.

Bob M.

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Deep Thought
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Re: Equipment Performance Measurements

Post by Deep Thought » Sun Sep 15, 2019 1:21 pm

The NRSC mask compliance measurements are to be taken no more than 14 months apart. Will the main transmitter be back online before the 14 months ends? Also,
§73.1590(b) Measurements for spurious and harmonic emissions must be made to show compliance with the transmission system requirements of §73.44 for AM stations; §73.317 for FM stations and §73.687 for TV stations. Measurements must be made under all conditions of modulation expected to be encountered by the station whether transmitting monophonic or stereophonic programs and providing subsidiary communications services.
That would indicate the IBOC operation should be measured.

I don't think the station would be exposed to a NAL should the main transmitter measurements run past 14 months as long as you document why they weren't taken within that time (and it makes sense).
Mark Mueller • Mueller Broadcast Design • La Grange, IL • http://www.muellerbroadcastdesign.com

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kkiddkkidd
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Re: Equipment Performance Measurements

Post by kkiddkkidd » Sun Sep 15, 2019 2:35 pm

I concur on Deep's thoughts and will add that a former FCC EIC told me that they are as interested in a stations diligence to comply as the compliance itself. I have zero experience with NRSC testing on an IBOSEC site.

If you want to cover all bases, do a test on the backup with a note that the station was running on the backup and then do another on the IBOSEC TX when it is back up.

I have a couple of regular NRSC clients that we test the main and stby tx almost every year.

Later,
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

kcbooboo
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Re: Equipment Performance Measurements

Post by kcbooboo » Mon Sep 16, 2019 7:33 am

Thanks. I really don't know when the main will be back in full operation. I think they're using it at night when they run lower power, then switching to the backup during the day for better coverage. They already sent two RF modules to BE for repair and that took 3-4 weeks. When they came back, one of the two modules didn't work so it had to go back to BE. The TX was putting out a lot of noise/hash all over the AM band, with emissions at -60dBc at best, even 200 kHz away. It was causing noise on AM reception several miles away on a station 80 kHz from them.

I really don't want to be outside in the cold weather, which is why I do my spectrums in Sept/Oct. I have to take four 10 minute samples at different spans and bandwidths because that's what the station's CE wants. When you include setup, tear down, and harmonic searches, it takes about an hour with the doors open or being outside, plus travel time.

I guess I'll wait a month and then take spectrums on whichever TX they're on. They're also fiddling with the pattern so they can get off the STA they've been on for a while, and that might be completed by then as well, which will mean a second set of measurements in directional mode.

Bob M.

kcbooboo
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Re: Equipment Performance Measurements

Post by kcbooboo » Wed Oct 16, 2019 2:49 am

Well I started with the IBOC measurements right at the transmitter. Those failed. High baseline noise level and more than just a few peaks exceeded the IBOC mask and even the 73.44 mask. We noticed the mod monitor seemed to be reading low negative modulation so we spent a few minutes checking the backup transmitter, which also seemed low. Even though the carrier level was 105%, a carrier level alarm was lit. So that has to be checked.

I then went out to my field monitor site 1km from the station. The 200 kHz span sweep baseline noise level was only down 50-60dB; usually it's more than 70, even out in the field. Harmonics were fine.

So I wrote the report and sent it in. I'll have to do the whole thing over again next month after the CE can spend some time figuring out what's wrong.

Question: when you guys do an EPM and the station fails, do you then do a retest as part of the original fee, or do you charge for each measurement session you do until it passes and YOU'RE satisfied?

Bob M.

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kkiddkkidd
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Re: Equipment Performance Measurements

Post by kkiddkkidd » Wed Oct 16, 2019 8:36 am

kcbooboo wrote:
Wed Oct 16, 2019 2:49 am
Well I started with the IBOC measurements right at the transmitter. Those failed. High baseline noise level and more than just a few peaks exceeded the IBOC mask and even the 73.44 mask. We noticed the mod monitor seemed to be reading low negative modulation so we spent a few minutes checking the backup transmitter, which also seemed low. Even though the carrier level was 105%, a carrier level alarm was lit. So that has to be checked.

I then went out to my field monitor site 1km from the station. The 200 kHz span sweep baseline noise level was only down 50-60dB; usually it's more than 70, even out in the field. Harmonics were fine.

So I wrote the report and sent it in. I'll have to do the whole thing over again next month after the CE can spend some time figuring out what's wrong.

Question: when you guys do an EPM and the station fails, do you then do a retest as part of the original fee, or do you charge for each measurement session you do until it passes and YOU'RE satisfied?

Bob M.
Since almost all of my yearly tests are stretched across the entire SE US at 5 to 500 miles away, I charge if someone wants a retest. I don't know that I have ever had this challenged but IF a station fails, I advise them to have the problem fixed, tell them what I think the problem might be and then ask the repairing engineer write a signed repair statement as an addendum to my test report IF they are certain that the problem is cleared. I have only been asked to come back to do a retest a couple of times since starting the official NRSC test routine back in the 90's.

I often get asked to help repair a failed tx under test. I absolutely will not do so during a scheduled test trip unless I have a bunch of extra time and it is a TX with which I have history. I have returned to a few TXs later to do repair work and then retest.

I believe that my job as a 3rd party test engineer is to do the test and present the results. Good or bad. I have absolutely zero control of the actions or inaction's of the licensee otherwise.

On the other hand, I have a couple of tests that I have done for years and the tx dutifully fails every year but yet it never gets fixed...
--
Kevin C. Kidd CSRE/AMD
WD4RAT
AM Ground Systems Company
http://www.amgroundsystems.com
KK Broadcast Engineering
http://www.kkbc.com

kcbooboo
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Location: East of the Mississippi

Re: Equipment Performance Measurements

Post by kcbooboo » Wed Oct 16, 2019 10:22 am

Thanks. In my case it's a very local station (less than 2 miles away) so travel isn't an issue. The CE will get around to fixing it because there are multiple issues and the transmitter just had two PA modules repaired by BE. It's just going to take time before he can get it added to his project list. One engineer, three stations, no IT person, so he's "the guy".

Bob M.

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