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Posts Tagged ‘Flexstar’

Carrier Drift & Diversity Delay

March 7, 2014 2 comments

Earlier this week, Tuesday to be exact, I noticed something not quite right with my diversity delay.  HD radio has added a little more complexity to our systems which requires delaying analog audio to match digital audio so when a radio switches between analog and HD audio there is no skipping or jumping.  This makes the transitions smoother in high multipath areas and only sounds like a quality change if the delay is set properly.  Knowing I had an issue I began  to look into it  when I received a call from our third-party frequency observer.  Our carrier frequency was off by -780 Hz.  Though within the legal limits, this was a large difference than the month prior.  What changed?

The technology for running IBOC, In Band On Channel, digital radio brought along some new challenges and some more things to monitor and look at.  In this case we have two things occurring:  Diversity delay drifting and a carrier off frequency.  With the new technology a source clock is required to maintain sync among all facets of transmission, and this is a 10 MHz reference.  All normal installations have a GPS signal fed to the Exporter which has a built-in receiver.  This produces the reference 10 MHz clock.  All normal installation uses this clock through the Exporter to sync their exciters, so the exciter is now synced to the same 10 MHz reference.  Most of the time this works.  In our case, on one station, it does not.  All four stations have Exporters located at the studios, and three of the four have no issues with the exciters syncing.  The third seemed to have some issues with this, so a 10 MHz GPS reference was installed at the transmitter site to clock the exciter directly.  This was my starting point.

It was safe to conclude that there was an issue, somewhere, with regard to the reference clocking since both diversity delay and carrier frequency were affected.  It was time to check things out at the site.  The ESE-110 GPS reference front panel display showed 2 green LEDs.  GPS lock and power.  Good sign.  The Flexstar exciter showed no errors.  Green LEDs and diagnostic screens showed good things.  I placed a spectrum analyzer on the 10 MHz output of the ESE.  I measured 10 MHz.  Actually it was slightly lower, like 10 Hz, but then again it is an older spectrum analyzer and probably needs calibration.  I used a TFT 844 to measure the frequency shift in conjunction with the spectrum analyzer.  Yup, it was there.  Since I wanted a third party measurement to confirm, I called him up.  I switched to the internal clock of the Flexstar.  Frequency changed and swung to +110 Hz.  Better.  The diversity delay settled down, too.  What was up with the 10 MHz input?

If the ESE output was within spec, and a call to ESE verified this along with the only indicators, the green LEDs, then what is up with the exciter?  Again, the exciter seemed to be good with the external reference according to the indicators on it along with the diagnostic screens.  I did not find the schematic at the site, another long story, so all I had was the operations manual and block diagrams.  I remeasured the 10 MHz signal.  I stretched out the bandwidth to look at the “hump.”   All the manual says is a max of 10 dBm, 0 dBm nominal, and it is used for carrier sync purposes.  They better modify that to say it is for ALL frequency references!  Mental note on  that.  I’ve been running this configuration for a year without issue, so what changed?  I stood there staring at the simplified block diagram of the Modulation Chain.  That PLL feeds the FPGA and D/A module.  Two different mixers.  Both having issues.  I read the short paragraph on the PLL.  The 10 MHz reference input is first amplified and put through an AGC loop for level stability.  I lacked stability.

My what if moment came at this point.  I have had zero, none, nada, problems for a year with my current configuration and a fairly sudden change occurred.  If they are amplifying the reference input, what if the amplifier has gone bad in some way.  I dug through the spectrum analyzer bag knowing I had a couple of in-line BNC pads.  I took out the -20 dBm pad, slapped it on the output of the ESE box, and reconnected it to the Flexstar exciter.  I gave it about 10 minutes, though I didn’t have to, and took a diversity delay measurement.  Yup, had to change it, so it was time to dial it in and see if it stays.  I got the delay down to a very respectable -0.0008 s.  At that value I should surely see a change if my solution did not work.  I gave it about 2 minutes and rechecked.  -0.0004 s.  I gave it 10 minutes more; -0.0005 s.  Before it was changing rapidly, now it seems to be locked in.  I gave a call to Harris.  While talking with support, I checked again, -0.0003 s.  OMG, this may be working.  I emailed my third party to take a measurement while I was busy talking with Harris.  No immediate response, but I was not too concerned.  The Harris tech was actually surprised at this solution, and after our talk concluded that a new PLL on site would be prudent as all indications now pointed to that as the culprit.

I packed up and blessed the site.  I returned to the station and took another reading.  The first in about an hour.  If it was drifting now, it would show it.  -0.0005 s.  I was beside myself at this point. What did I stumble upon?  It has never been this stable.  Before leaving for the day and my tax appointment, I took another reading:  -0.0009 s.  So far so good.  After my appointment, we were out eating dinner (yes, we owe the government a couple of bucks) I received an email from my contact.  He listed the times of measurements and the error, the last entry was “6:47 PM.   0 Hz error ** Wow!  What did you do?” My solution was holding!  I came into work this morning, and I checked my delay again:  -0.0004 s.

I now have a PLL module on order with Harris as we have no idea how long this one will last.  From what I can figure the amplifier section of the PLL has an issue.  The 10 MHz reference was getting distorted and creating  a new frequency that offset the carrier frequency.  In addition, the distorted signal was “outside” the specification for the unit to lock the diversity delay which was free-running allowing it to drift over a half second.  Talking with a colleague we both concluded they may want to install a test point or provide a software controlled pad on the external 10 MHz input.  For now, the problem is solved.  I am tempted to see how long this lasts or if there will be further deterioration causing drift once again.  Happy troubleshoot!

 

Cheers!

Travels, Work, and More Work

June 29, 2012 Comments off

Wow, it seems to be forever since I posted.  Forgive that.  I bet you expect juicy details on super secret stuff.  Well, not exactly.  Recently I did travel, and since being back I have been busy.  Shoot, I was busy before the travel.  Does work get in the way of vacation or does vacation get in the way of work?  Will we ever know?

Vacation was great.  Part of that was to visit the Elenos factory in Italy.  I enjoyed meeting the crew out there and talking shop.  What I saw was quite impressive and the dedication and passion behind the product is amazing.  With that we may see Elenos become a player in the transmitter market, so stay tuned.  From what I understand I may be receiving one to test.  Did I mention they did win a Cool Stuff award at NAB this year?

Of course I get back from vacation, IT Dude goes on vacation.  This always equals some trouble.  In this case it is Marketron vs. Windows 7 and a Ricoh printer.  After a whole week, we still cannot print from the new machines.  They print locally, but not through Marketron.  I think I am overlooking something that IT Dude will notice right off.  That is the true difference of dealing with something day-to-day versus only on occasion.

Do I dare mention the Harris Flexstar?  I should write a whole post on just this.  Yes, I continue to have Exciter muting issues, though not as bad as before.  To make a long story short, we know for a fact that the Flexstar cannot handle too much data.  It bogs down and eventually chokes.  The only way to recover from the mute is to reboot.  I wired up my remote control to the Flexstar restart input.  This is pin 13 on the Remote User Interface of the Flexstar itself.  A contact to ground and the Flexstar will perform and cold boot.

I have been fine tuning my Burk ARC Plus installation and utilizing the AutoPilot program a bit more.  Now if we can only get Burk to support SNMP within the ARC Plus removing the need for AutoPilot they may be on to something.  In the meantime I have created a fine custom view that shows the basics of all my transmitter sites.  Attached to the touch screen monitor, all it takes is a touch of the screen to execute a function like STL switching or rebooting the Flexstar exciter.  In addition I am utilizing SNMP with my Eaton-Powerware UPS’s by adding a network management card to the UPS.  Currently four are up and running and I monitor on AutoPilot input and output voltage, UPS load, time remaining, and battery charge level.  As I learn more about SNMP I may have status notifications if a self test fails or whatever else I can find!

Maybe my next post will get into some dirty details.  If there is a subject you wish to see covered, drop me a line.

Cheers!

Categories: Equipment, Management Tags: , , ,

Hell Week or Just Plain Busy

January 21, 2012 Comments off

As promised a recap of a busy week.  If you follow my tweets, your sure already know we had a busy week.  Harris, RCS, AT&T, and the regular stuff just piled on.

My Harris Flexstar RF mute issues sprung up on me this week.  It has been on hiatus for a couple of months and then an outage on Monday and two within 15 minutes on Tuesday.  So, in answer to a phone call today, no there is nothing really to do but make sure the latest and greatest in software/firmware release is installed.  If you do not have that, you will not get much in return from tech support.  I updated the Flexstar to Exgine 4.40 and DSP to 8.33.  Since this had to be done, I had to upgrade the Exporter to 4.3.1 and the Importer to 4.3.2.  This now sets the clock on if I continue to have issues, and knock on wood I have not had an issue since the update.  On that note I still need a good answer to why HD data should be able to knock me off the air?  So if you have issues with your Flexstar, update it.  Then document exactly what the issue is.  Once you have all that ammunition, give tech support a shot and see what answers you get.  Do not be surprised if you feel a bit helpless.  The HTHD+ as an RF amplifier is great, they just need to fix the most critical piece, the exciter.

While transmitter issues were occurring we were hit with an RCS NexGen crash.  All 3 station decided to play the game.  Console control stopped, database communications became sketchy, and the whole system was just sluggish.  No apparent reason.  We noted it had to do with network traffic, so some box is flooding the network or we have a physical device that has an issue.  On that assumption we changed out the brand new Cisco switch purchased from RCS with an old 1GB Dell switch used on the old DAD network.  Everything began to run much more smoothly.  IT and RCS check the switch and all seems good.  We still have yet to switch back.

If this was not enough, concurrent failure of a T1 to a transmitter site happened.  I was on the phone with AT&T when the Flexstar decided to drop off.  It must have been a funny picture having me on the phone with AT&T while I was poking the remote control switching us to our Aux transmitter.  Multitasking at its best.  AT&T replaced a repeater and a snap-jack in the CO.  No dispatch to the site.  This particular CO seems to be having many issue of late.  We seem to cycle through which T1 goes down.  Annoying, but they were on it and problem is solved for now.

In addition to running around dealing with this, I still am working details on the Burk remote control system.  I have the sites up and in theory they should all see each other.  Reality is a different story.  I can see one site from the shop, but not another.  While at the “offending” transmitter site, I was unable to see the other sites from the ARC Plus.  Here is the odd part.  With AutoPilot I can see all the sites.  I get readings and all the good stuff.  With AutoLoad I can see all the sites.  Even at the transmitter site I had to visit I was able to see all the sites.  Why the ARC Plus does not see the others, and the site list is in it, is beyond me.  I have an inquiry to Burk on that one.  I am also going to contact Moseley to delve into a potential issue with the LanLink.  I need something a bit more robust.  A 6 mile shot should not be that difficult.

I can say at least I was busy and not bored.  Mix this with home life and it was quite a week.  I’m glad to be able to sit down and spew this out.  If you have experience with any of the items discussed or have any items you wish to see a discussion, please drop a line, leave a comment, or give a call.  Now let’s see what next week brings!

Cheers!

Same,but Not

March 11, 2011 4 comments

Ever get the feeling things stay the same, but then discover they are not?  We had anotther UPS fault this week. This time on the processing rack. I did the early morning swap without incident. Off air time was that of the reboot. Phew.  Then tonight a surprise;  station drops off the air!

There are many frustrations when dealing with old infrastructure.  We have an Aux site for three stations, but only the remote control for one operates it!  So, said station goes off, it calls me and I go to the Aux transmitter:  no audio!  I instructed my assistant to turn on the Aux site, if not him I would have to dial up the Aux site and turn it on. Then I would dial back to the main site to make sure all is off there.  Annoying and a waste of time.

So much for my rant.  We need a better remote system!  Anyways our Harris HDHT+ dropped. I could not find a problem. Ran it in a load. Ran it back on air. Nothing. No log entries. These are the very symptoms as last year. I suspect the Flexstar exciter did some barf. Again no logs to confirm or deny it. I checked UPS logs and found no indication of a power event. I looked at other devices for tell-tale signs, and found none. For piece of mind I rebooted the exciter. Let’s see where this goes. Of course all this occurs days before I take a few days off.

Next I will lay out what should be a reliable remote system.  All busy work, but becoming necessary. That along with how to deal with the emminent NextGen system being forced upon us. Our 20 year old infrastructure cannot handle this extra hardware.  No space and no power. I should detail that story in a future post!

Cheers!

Categories: Equipment, Management Tags: , ,

Harris Flexstar Update 6/17/2010

June 17, 2010 Comments off

So for all waiting with baited breath on an update regarding the Flexstar situation here.  I installed a beta update to the “loaner” Flexstar exciter back in May.  Guess what?  We’ve been on the air continuously since the update and the diversity delay has be quite stable.  Check with Harris and try to get an idea of when they plan to release this version.  I thought it would be this month, but I have not heard anything.  Then again I usually have to ask for stuff.

What have we done?  I do not recall what I wrote before and am too lazy to look back.  We changed back to a UDP stream from the TCP.  The bottleneck that was being experienced the Flexstar did not like.  We forced our Intraplex T-1 NIC (network interface card) to 10/Full on both ends.  On the managed switch we made the port feeding the Intraplex 10/Full also.  At the transmitter site we decided to take a variable out and feed from the Intraplex to the exciter directly, using a cross-over cable, and set the exciter NIC to 10/Full.  This all dropped the jitter down.  I recently became aware of someone who discovered that their DS-64NC card in the Intraplex was causing T1 issues. Once replaced they stabilized.

I have been monitoring and checking every 3 to 4 days on the diversity delay.  Still good.  Mask is great.  I feel that we have moved in the right direction.  Now of course this is a loaner exciter, so I still wonder what happened to our last exciter and what physically may have happened.  I strongly suspect that this current “loaner” will be come our “permanent”, but no word yet.

A little digging on this part sure has gone a long way.  Now we just need to close the project.  That will happen when the release of the Exgine and Flexstar application are released.

I really hope this has helped some of you out there get your boxes on track!

Categories: Equipment Tags: ,

Harris FlexStar Issue

January 11, 2010 3 comments

I mentioned awhile back that we were having mysterious outages, or off-air events, with our HTHD+ transmitter.  This began May or June last year and we’ve spent much time working with Harris to determine where the problem was.  Each time we would try or look into something  as they suggested.  The events were random and quite annoying.  Obviously the station PD was becoming quite annoyed.  Random issues are the worst.

As we followed suggestions, we connected the remote control to various status and metering locations to determine what and where our RF mute was occurring.  We ended up metering the FlexStar exciter forward power.  We connected a status monitor to the RF Mute status.  Was it the transmitter telling the exciter to mute?  Was the exciter muting on its own?  More questions and no answers.  Was the APC circuit cutting out?  Nope.  We began to catch events that ruled out the transmitter and APC.  The exciter forward power muted without any mute status.  Now what?

Next became a look at the HD data network.  Could the data cause an RF mute?  It seemed a reasonable question as the exciter does lock its PLL to the 10MHz clock that is derived via the Exporter and GPS.  We began to gather PLL logs.  We did discover some latency that could affect the PLL, but it did not explain why or how it could mute the RF.  As we are running in hybrid mode, we really do not want anything that messes with the HD to mess with our analog.  We continued to gather more logs and information, but an no point were we able to tie anything together.

Harris decided they wanted the exciter for bench testing.  After nearly two weeks of bench testing we did receive an email stating that they captured an RF mute situation and it had nothing to do with the HD data or network.  Now we wait to hear what internal issue is causing the random mutes.  This whole thing has become quite an interesting ordeal.  Sometimes you learn more than your really wanted or needed to know.  Stay tune for the final word!

Categories: Equipment Tags: , ,

Transmitters and their Quirks

December 20, 2009 Comments off

We spent the week working with Harris on the HTHD+. More precisely we have been working with them on the FlexStar exciter. Apparently we have some sort of PLL anomaly, or at least that is what we are investigating now.

We have limited connectivity to our transmitter site, so we use a single T1 circuit that carries our main audio and our HD data. This bottleneck seems to cause a clocking issue and when it gets too far out of whack (for lack of a better descriptor) the PLL goes nuts and mutes RF on the exciter. With more information from our frequency monitoring service we discovered that the transmitter was drifting in frequency, too.

We shipped our exciter back for evaluation and have installed a loaner. We went to air on it Friday, and so far we have been on the air since. I will be checking the PLL logs we are collecting to see how this exciter deals with our bottleneck of a data network.

I cannot blame any manufacturer here. I do feel that iBiquity could have/should have done a bit more testing of their algorithms and encoding so such issues could be avoided. There are many stations with limited bandwidth to their transmitter sites. If we were not forced to jump on this HD bandwagon so soon, maybe this situation would never have happened.

Categories: Equipment Tags: , , ,

Harris Fix?

October 21, 2009 Comments off

Apparently we me be on the road to the answer of why our HTHD+ transmitter randomly drops off air. If you have followed my posts these random events are annoying to say the least. Recently we discovered the transmitter recovers on its own within 2 minutes, a long time in radio land. What is this potential solution?

Set the Exgine Buffer such that the Buf Used and Buf Max is in the 20-30% range. We moved ours from Default to 0.836 and the system seemed to stabilize. We still experience Exporter Sync Unlocks, but are not as often. Also when using thos setting the Lock Indicator does not swing as much. This will count down to zero, go negative, reverse, and “swing” between random limits. Apparently if the swing is within some tolerance the sync indicates a lock and the buffer is running optimal.

If the buffer is over utilized there seems to be a DSP barf which mutes the exciter. Seems odd that this could happen, but since changing our settings we surpassed our 2 week wall and shut offs. After checking this morning the sync was unlocked and we noticed our T-1 circuit took a hit. Makes sense that some corrupt packets came in and caused loss of sync. We await a re-sync. Too bad there is no good way to remotely monitor this.

I will keep on top of this, so look for tweets and future blog updates.

Categories: Equipment Tags: , ,

Moseley SL9003Q AES Gotcha

July 19, 2009 Comments off

What a week.  AT&T takes down our T-1 STL without notice.  An aerial to buried cut-over and their documentation is all screwed up.  Sure enough, off the air!  Then I discovered the hard way that when we switch to our aural STL the main transmitter, HTHD+, has no audio, yet the backup, HT-25, does!

What did I learn?  The AES audio from the 9003Q has a “no audio” bit set in the output card.  The Flexstar exciter reads it as no audio and thus no audio on the air.  Huh?  I receive a 3 year old tech sheet from Harris stating a modification to the Moseley output card.  I perform the modification and now everything works.  My question:  Why did this output work fine with our original Flexstar exciter but not this one?

Earlier this year we had an actual failure of the XLR input board on the Flexstar.  Exhibited the same no audio issue, but from both AES sources.  This time I assumed the same thing.  When I found out about this modification, I was floored.  My predecessor did not document this?  As I mentioned, we have used the auxiliary STL before without issue on the Flexstar.  Or had we?

All I know now is that it is fixed and we are covered as we should.  Making discoveries this way sure drives you nuts.

Categories: Equipment Tags: , , ,

Harris HTHD+: More?

June 30, 2009 Comments off

Yesterday we had our HTHD+ drop off the air again. When I arrived at the site the mimic panel showed an Exciter Fault!
1. Was it the Flexstar at fault?
Right now we are assuming, between us and tech support, that the PA module in the Flexstar is not happy with something. This is based on a fluctuating forward power of a few tens of a watt while the APC voltage remains constant. To troubleshoot this we await a new PA module for the exciter.

2. Did something else cause the exciter to fault?
What if the IPA is asking too much from the exciter? Seems to be stable and the fluctuations on its forward power follow that of the exciter, so it appears to be working fine.

3. What was the fault?
There is no indication nor have I found log files that would suggest what actually occurred. I need to research to see if the Flexstar keeps any log files. As it is an early “software controlled device” I suspect not or it is well hidden. A call may be in order.

On that note, when I powered up after tests it has remained on the air since. I will deal with the power fluctuations as long as I can maintain legality and on-air. We are a BTC/Navteq station. Believe it or not it is important for us to run HD. We will see if a new PA module actually works. If not, I will suggest a swap of the IPA.

Categories: Equipment Tags: , , ,
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