I had a similar issue earlier this month, I’ll relate the story though I doubt it will help because no final determination has been made yet.
About 3 months ago I took an omnia one from our studio up to the transmitter site so I could feed the main transmitters analog (we’re HD up there too) with composite and get rid of a lesser processor that had been up there, and it was feeding the main with analog audio to the exciter (harris Flexstar HD). Our STL is a harris HD-LINK, I’ve Got AES going in and can take AES or Analog out on the RX side.
Well we started getting dropouts a little over a month ago, very intermittent. Now I’m a busy guy with a ton of sites all over the vast state of Colorado, I’m on the road a lot, the occasional dropout really wasn’t the highest priority. Was it the automation? Was it the STL? Who knows….I don’t have a loggin system setup that could help me pinpoint the trouble, and it is infrequent.
Management started to complain it was getting worse, but I hardly noticed it. Went up to the site on an unrelated issue (actually to a different site for a contract employer) stopped in to check my stuff and found the room blower was dead, and it was probably 80-85 degrees in the room. Propped the louvers open, room cooled down a bit. Called grainger to try and get a new motor, kind lady on the phone tried to find something to fit, said she found one, put in hold at the local store. Now the site is really loud even with just the TX on, I’ve got a little radio up there and you can barely hear it over the noise, and it’s turned up to distortion. It also likes to flake out from all the RF. Needless to say I didn’t notice anything while I was there, and every time I looked at the TX, audio meters where moving right along.
Fan motor at grainger was clearly not the right thing when I got there….it was Friday. Guy at the counter found a good one but it would be Monday morning before it arrived.
Monday came, got motor, went up to the site, installed it, all good. Get down the hill (where my phone works) and got an email stating the dropouts are getting worse, was I doing something? Well no…I wasn’t. turned on the radio everything seemed fine. Went home to clean up. Got call ten dropouts in the last 30 minutes. Funny, didn’t hear anything on the way home.
Set up a radio and pulled up the stream on my computer, to see if they were both dropping out. Now the stream has a delay so it was a terrible cacophony but after some time listening, I heard several dropouts on the FM, none on the stream. OK, it’s not the automation. I listened to the HD and swore I heard a dropout on analog and HD in the same place. OFF to the studio I went, at about 6pm.
I’ve got a Tektronix 764 digital audio monitor, so I patched it into the system. We don’t have a master clock per se, but we have the harris HD equipment setup as they want it, Exporter locked to gps, sending a 44.1Khz word clock to the impoerter, and doing SRC on the AES inputs for main and delay audio. I patched the TEK into the chain one channel between exporter main out and STL in and the other between the HD processor and the exporter in. I let it run a log all night. Didn’t hear any dropouts while I was driving in, at the studio, or driving home.
Next morning I’m driving in, get a call about dropouts….I’m listening and I don’t hear them…..then a moment of genious, I got a new HD radio in the Van back in December. I forced it to analog and they were there…..well I guess it’s not dropping on the HD after all. In the studio I listen off air but the Day sequerra mod monitor is HD also. I force it to analog and now I hear them there too. The tek showed no dropouts (though it did complain about sync)
I was pretty sure I was heading back up to the transmitter site, but just for giggles I setup my laptop and my newly acquired SDR dongle and antenna, tuned up my frequency and watched and listened. Every dropout I lost my MPX…..up the hill I go.
When I get to the transmitter site I brought my tek and set it up between the STL out and the omnia one in.and listen to the stl on headphones. No drops. I watch the exciter and the composite input is dropping out, I watch the omnia output meter and it is dropping too (the meter is normally setting on input). Hah…Omnia is the problem.
I yanked it out, and hooked up the analog line from the old processor (it was still sending its composite to the backup tx). Listened for a good while before being satisfied that I had found, and bypassed, the problem.
That omnia is sitting 6 feet away right now, I haven’t gotten around to testing it yet. My suspicion thus far was, I don’t know how long the blower was out or how hot the room got, the omnia was mounted in the TX above the exciter, abd I figured maybe it got toasted……
But now I’m not so sure…….
Lessons learned: Don’t forget to force to analog if you’re on an HD radio!
I’m also getting a better remote control system setup at that site, current one has no way to monitor temperature, or the fan, or really do much other than tell you readings and turn on/off the transmitters, It’s legal, but barebones…..its also an old VRC3000…….not hooked to autopilot. Computers don’t last long up there anyway…..replacing with an Audemat control silver, which is currently 4 feet away from me and should be installed next week.
So JIM if you read this all I’m sure it didn’t help much it seems your situation is different….or maybe my situation is different than my suspicion….
IIRC the omnia one xlr to rj45 adapter has two inputs and one of them is for sync though I’m pretty sure it is not necessary (AES is self clocking), and In my setup at the TX site, What would I put into that sync anyway? Nothing else has a sync in….it would be pointless.
From: Jim McDermott [mailto:email@example.com]
Sent: Thursday, March 30, 2017 10:15 AM
To: CRTech <firstname.lastname@example.org>
Subject: [CRTech] AES-EBU Dropouts
I admit, I've never done much in the digital audio realm, but when I got a new processor and could link up through AES-EBU, I'd thought try it. Somewhere in the chain, however, I'm getting short dropouts, maybe 1/2 to 1 sec. They are very sporadic and unpredictable, but may happen only three times a day up to several times an hour. I had to make a cat 5 to xlr adapter to get from the Axia out to the Sage Endec in. When it works, it sounds fine. Any thoughts?