Month: November 2021
A quick look at the GatesAir UHF TV transmitter
This one is shaped like a big rectangular friend. It’s a GatesAir ULXTE-30, which can give you 19.2 kilowatts out of its 30 amplifier modules.
This one’s practically brand new and is pretty much an illustration of how densely you can build a LDMOS based solid state linear amplifier! Gates says it can give you up to 45% efficiency which is pretty dang good for linear amplification – a necessary evil with transmission modes that use amplitude keying such as 8VSB, QAM, and COFDM. All the major heat sources on this unit are cooled by a standard 50% mix automotive grade antifreeze solution circulated through tubes in the modules.
From top to bottom:
I forgot to annotate this but the harmonic filter is that ridged black tube up top above the cabinet. It doesn’t get dissipate much energy at all and requires no active cooling.
The exciters are responsible for generating the RF carrier, modulating it with data input from the broadcast encoders (back at the studio in our case), and applying precorrection for frequency and group delay response of the amplifier and filter system. GatesAir calls the latter their RTAC System, for Real-time Active Correction. Only one is actually on air at a time, but you can switch exciter in case of one failing, or to allow you to do things like update the software on one while the other is on air.
The controller provides local and remote (web interface) control and metering of the transmitter’s functioning as well as controlling the power and cooling systems. It has canbus communications to the rest of the system.
You can see that the modules below are in three distinct groups. This is because the whole thing is of a modular design; lower wattage units may have only one or two of those ten-pack units and can even have the cooling pump station built right into the bottom of the cabinet! This one’s just packed with power, though. The power supplies are slide out modules with air cooling – they’re pretty high efficiency so they don’t need a lot of airflow. The weird little pick on the door is used to lift the latch that holds them in if you have to remove one.
In each group of modules, the upper two are a preamp and driver stage, and the rest are final power amplifiers. The output of each goes to a backplane with a combiner that feeds into the large black combiner seen in the back of the cabinet. The two glycol cooled reject loads absorb any reflected power caused by imbalances in the system.
Look carefully and you’ll see I placed a pink asterisk at the top. This is indicating a small yellow wifi router. If you don’t use this I’d recommend unplugging the power lead to it. It’s not vital for anything, it’s basically just used if you have a wireless tablet used to get into the web interface instead of a device on wired Ethernet.
The pumps are external on this system. They’re the unit on the right here. To the left is a combiner and filter unit that’s combining this and the output of another transmitter to a common transmission line and antenna. There are four variable frequency drives on it, two control the pumps and two control the fans outside on the radiator.
The heat yeeter:
To date the only thing I’ve had to do with this transmitter was replace one power supply module that tanked under warranty and top up the cooling system. It’s a good tall beige friend.
Yes, I’m glad they resigned this…
So you know how GatesAir has that cool little integrated pump station for their liquid cooled transmitters nowadays? Yeah uh it was not always that nice. Presenting…. the older one circa 2009. It’s interesting.
This poor thing was running on EMPTY, time to juice it up! Let’s see, uh…. wait. You can’t just let it draw the solution in out of a bucket, you must use an external pump to force it in there! The expansion tank is very much on the wrong side of the pump to make pressurizing the system the same way you do with the newer systems possible.
Oh and it’s all on the outdoor side and the pumps get all nasty due to weather exposure. Both of these units have one bad pump each. Yaaaackkkk.
I unfortunately didn’t get pictures of the mess that occurred when the charging pump blechhhhh’d all over the floor or when that main vent pictured above inexplicably yacked on the wall behind it but suffice to say mess was made here.
As I was at the tower the other day I found myself thinking the elevator motor looks like a mushroom growing out of the gearbox.
I spent a few hours working in the little comm shelter at the top, then descended through a bank of fog that rolled in and back out as the elevator slowly sighed and buzzed its way down.
As I neared the ground, I spotted some big mushrooms in the lawn… I went down to take a look.
And then on the balcony— another, but this one was, uh, a little different
Curious. Apparently it may have been left over from the original channel 13 VHF KOVR transmitter… I found a local ham’s page showing some far happier tubes from the same rig! Pretty cool. Kinda odd it just sat out back there but, okay.
More sunset:Read more “Pleasantly fungiform”
There’s kids. On the ice. What’s a dinosaur to do when there’s kids on the ice. Quick, somebody call their mom
Pretty sure we got a viewer call from Eeby Deeby overnight.
My cat is sweet bebby
the forbidden mountain dew
This is a post about transmitter juice.
Seen here – the sight glass and automatic air vent at the high point of the system.
Until today I never gave too much thought to this cooling system, and it seems I should have done so more often as it was sitting there at zero pressure. Yikes. In fact… its pressure had gone so low that the janky little pressure gauges were doing this.
I have no idea how it managed to slip around to the wrong side of the pin, but it’s a really garbage tier gauge so I guess that’s no surprise.
Refilling the system is a matter of just opening the vent caps on the air vent valves, admitting fresh coolant to the system via that tap on the pump suction side, and creating backpressure in the system by closing the suction side valve partially. This causes backpressure to build up in the system and compress the air bladder inside that tank while making the pump draw more coolant in from the source. Once it’s run for a while you can close the vent caps on the valves so they don’t, uh—
yeah I wonder if this is why and where the pressure all got out — all the vent caps were open, and, ew
The instruction manual on this GatesAir system states that you don’t really need to worry about overfilling it because that spring loaded relief valve will lift and burp out the excess if it gets over the maximum of 75 PSI.
Both of the two transmitter cabinets in this installation have their own cooling system, and there’s a third for the glycol solution cooled RF loads. That one’s holding its pressure just fine.
Now for… uh… cursed things
Speaking of toilets— it was time to give amplifier #3 on the Space Station Toilet a new Barnstead filter. As I experienced previously, touching anything on the Barnstead led to leaking as the shrunken hardened gaskets started crumbling. I think I’d kinda vaguely alluded in a previous post to this filter holder unit having hilariously cursed input and output connectors, but I hadn’t gotten good pictures of the thing. I had, however, looked all over Thermo Fisher’s catalogs and webpage trying to find the proper gaskets for this thing and could never find the same series of connectors. Their current models of the Barnstead filter holders do not use this same stuff. This raises the question of which of the two is true:
1) Thermo Fisher switched suppliers for their filter holder assemblies at some point in time, the new manufacturer uses a different system, and they do not have parts in stock for the old system.
2) Thermo Fisher has realized this old system is complete garbage and does not even want to admit to having ever made it.
I’m leaning towards 2. Without further ado, here’s… this thing. The fitting can swivel a bit, but doing so tends to lift the two pins out. You can see their heads here.
Removing the pins releases the connection completely.
Looking down the bore at the weird gasket:
And finally, the connector itself, with BIG RAUNCHY MOLD MARKS THAT JUST MAKE LIFE DIFFICULT:
YUCKY STUFF AHEAD
So my coworkers had told me in the past about some kind of “carbon” that tended to circulate in the system on this transmitter, likely contributing to how it lays waste to the cooling water flow sensors. I was a little baffled, where would this come from? This system is just supposed to be full of PURE deionized water to maintain proper electrical resistivity and not clog things up. Well then, uh—
Imagine my amazement and horror when I dropped the Barnstead filter housing down and just saw it fill up with this inky yackage.
I poured it into a clear plastic water bottle for inspection. It looks like diluted India ink, and thankfully, smells like nothing. Coarse particles settled to the bottom, but even after sitting a couple hours, not everything settles out. I’m wondering if this is the result of the Barnstead filter just releasing small activated charcoal particles when the water flow stopped and reversed a moment, or if that’s really just… floating around in there. If so, where is all that coming from? Ew ew ew ewwwwwwwwwwwww
Greetings from the clouds…
The new superheroes have dropped and they’re pretty weird
Catgirl thoughts or something
So in my last post I got really mad over Grass Valley Group products really not handling blatantly obvious bad timecode well. Rest assured this also affects their iTX master control/automation product and I’m really glad that didn’t toss its toys right out of the pram on my shift.
Well, I tracked down the problem, and it’s a very bad one with the main and hot spare master timing generators being completely hosed up and the automatic changeover being a spaz.
Let’s just say the only way out of this one is an emergency capital expenditure request that’s being made as I speak. The servo balanced LTC output is somehow half burned up on the working one of the two and this can’t be fixed without taking the unit out which means NOOOOOO TIMECODE *whistle boing*
That remains unfixed but I’m really happy for an unrelated and wonderful reason.
Anyone remember when I had THAT director of engineering back in Miami who made a huge deal about it being totally unacceptable for me to reflect as anything outside of my boring old birth assigned gender role?
Yeah that’s apparently not a thing at all here. I’m so glad. I think at worst maybe one of my coworkers was very slightly confused because he was used to referring to me by male pronouns and I guess kinda questioned that for a moment but that really doesn’t bother me at all. I have thought maybe I should introduce myself using they/them to avoid confusion but… whatever works.
Oh and yes this was me being rather lazy, really I just wanted to wear my favorite dress at work somehow and then realized I had a set of cat ears that matched it! It worked out so well and everyone was trying to figure out what anime I was from. Well….. I’ve often thought a somewhat ridiculous anime about broadcast engineering should exist— think maybe what you’d get if you crossed Azumanga Daioh with a TV and radio station. Meow.
I wish to point out something ridiculous here. In the photo I took in the dark, a lot of that light reflecting off my dress is a whole stack of windows open on my desktop PC as I give our ChyronHego graphics systems their weekly, uh, wash, rinse, and tri-color foaming wax or whatever. These things are high maintenance and just as I was about to leave for the afternoon to go take a cat nap, the Camio Luci component of…. whatever….. Blew The F Up.
Guess what turned out to secretly actually just be Software As A [dis]Service with a weird local hardware-ish interface to the on site newsroom automation all along?
*Scooby Doo villain unmask scene!*
Yeah apparently ChyronHego support told us yes they’re down and we can’t generate any supers or lower thirds because…. Blurrrrrppp. Excuse me, I think I need to go sharpen my claws on the cat tree.