Another day, another case of being thoroughly perplexed by RF Central gear—
When the mast goes up but the signal doesn’t go out, it’s time to investigate.
The forward/reflect/12vdc return meter always seemed to show 00.0 if the PA was off… -1 if the PA was on, in any field.
TWO different bad amplifier units…. one was waiting on the shelf as a spare, one just came off the truck.
So what’s inside? I forgot to take a photo but if you remove the hex screws on the back it reveals a Stealth Microwave SM2025-44L, 25 watt linear amplifier for 2000-2500 megacycle DVB applications. Sadly. Stealth Microwave is long gone.
Interestingly the amp bricks are specified as having an internal output isolator. Nifty.
The other major part inside the amp brick is a bias tee that splits 12vdc power sent up the coax out to run the fan and the amplifier.
And now, it gets… horrifying.
I found a datasheet on the SM2025-44L and it’s specified as taking a mighty 8.5 amperes. I mean, at least it isn’t gonna arc furnace anything, but the voltage drop CANNOT be nontrivial anymore.
This has to get to it on the coax. The coax from the indoor unit in the truck to the outdoor amplifier unit is not a short sweet little run. See the big black coil up the mast in the first pic? There’s probably at least 45 feet of coax in there, plus another dozen at least to land it from the feedthrough in the roof to the IDU in the rack.
WHY DID THIS EVER WORK AT ALL? Or does it? I don’t….. I can’t even——- No——— I need to go home and collapse in bed and place the kitteh on top of me and stop trying to think for this week. DONE. I’m so done. What the hell.
Holy heck. I think I’m looking at a piece of terrible broadcasting history here— the Tektronix RFA400A.
It ran Windows NT Embedded.
It has a dual Pentium Pro Slot 1 400 Mhz backplane PC inside, which does not boot, and chances of finding a replacement are probably zero. I’d guess probably about 31 of these boards were ever made and the other 30 have already been thrown in a Homer Paint Bucket full of acid by some gold scrapper in their backyard.
I’m estimating chances of being able to repair this thing at approximately HELL NO percent. Thankfully we have far better, newer test equipment in place already. YEET!
Back in the 90s I ran the camera for my school’s morning news production. It wasn’t exactly a well equipped production; we just used the video out from a crappy RCA VHS camcorder on a tripod and a plastic Radio Shack mic plugged into the thing’s audio input.
One day I aimed the camera at the monitor (which was just the usual television set on a rolling cart with a VCR on the shelf below it, standard 90s classroom fare…) and it created this fabulous “infinity mirror” kind of pattern. If I aimed it just right, it’d keep going, otherwise it’d repeatedly erase itself to white or black and just flash.
Apparently I’m far from the only one who appreciates this kind of silliness.
The original “Scanimate” systems used video feedback through analog circuitry to work their amazing magic.
Here’s a 1984 exploration of video feedback dynamics by Jim Crutchfield:
I only kinda recently discovered what hilarious things you can do on a video mixer/switcher, and it seems almost like the cheezier the device is, the better? The ones that are made for home video editing seem to be particularly great as they have built in frame sync. In fact, it sometimes amazes me that the big HD professional switchers for live production and editing DON’T handle unsynchronized sources elegantly. I could see it for oldschool analog ones.
The Snell & Wilcox Kahuna switcher at WSVN had me spoiled – as long as the video input format on any given port matched what you set it to expect in the engineering config page, it took it just fine, regardless of sync. You only needed it to be synchronized accurately if you wanted to avoid some otherwise unavoidable latency (up to a frame or two – hardly terrible, but SOMETIMES noticeable as a slight lip-sync issue).
The Sony switchers where I work now will exhibit vertical roll problems if you don’t have things in sync, which is, um, special. A fair number of Evertz converters and black burst timing distribution to everything keep it all happy for the most part.
Now, this is all basically fine if you are using professional grade equipment with a correctly operating master timing generator. Each video source (VTRs, cameras, etc) will use a phase locked loop to synchronize their video timing to the sync pulses and burst phase of the master generator. In the old days, it was necessary to use delay lines, either built into distribution amps, standalone, or implemented using long pieces of cable to match the delays throughout the facility to make sure everything reached the switcher in the same timing. Nowadays with HD video, SOME buffering is added to give you a few lines of leeway. I’m not sure exactly how much in any given case, but the Grass Valley Group CQX switches are advertised as buffering and time-shifting by up to three video lines in the event that the sources hit it a LITTLE out of sync, so they can provide perfectly timed output. They can also do some basic clean cut and crossfade transitions onboard.
Nowadays since there’s no analog color subcarrier to deal with phase synchronizing, and it’s basically just more important to have a robust sync pulse than a whole video waveform, trilevel sync is becoming more commonplace. That’s just basically a pulse that tells everything “please start your first video line here”.
The really cheezy wonderful switchers that are the most fun to play with were designed to work with consumer grade equipment that gave you none of these luxuries. They just had to deal with the video coming in at whatever timing it did, so they incorporate a frame sync buffer on at least one input. While this can lead to some delay, it offers a lot more flexibility as to sources.
It also allows you to create some amazing feedback loops with video coming back not quite in phase and essentially crapping rainbows.
I’ve already babbled about the underlying technology more than I intended to, here are some pretty pictures.
The Videonics unit used here is actually a rather powerful little device; it’s a microprocessor driven unit with onscreen display and menus brought out to your preview monitor. Downside to this is, you have to use a monitor just to see what you’re doing on it. Eh, ok.
Examples of raw video feedback:
In high def!
In many cases it is possible to use a video mixer looped back to itself with no external sources to synthesize some trippy shit. 😀
It tends to lend itself to a flashier dynamic, which I don’t like as much, but you can with careful manipulation of the controls get it to generate some more stable effects.
(Definite epilepsy warning on this video!!)
This video has more of the slow moving, blown out full saturation effects I prefer:
Dreamy little seascape….
So there were also some really bizarre devices made that didn’t bother with the whole sync thing and let you basically fade/wipe to a solid color, pause recording on your VCR, switch source, then fade/wipe back in. Here’s a video review of one of them I have. This thing… is…. HEAVY. It’s also fun to add into a feedback loop.
Raw video from a Sony XV-T33F which is a bizarre title generator with drawing tablet for input. It can also do the offline fades/wipes, but it can also do some peculiar color animations and stuff that are amazing in and of themselves.
I should draw a bunch of shopping mall interiors on mine.
(Not really electronically manipulated, but this video is the inspiration for the thought above)
So, what’s odd is, while I’ve seen a number of examples of the mixers (particularly the Panasonic WJ-MX12) being circuit bent, along with the Sony video sketch titler… really most of the bends I’ve seen just give them some extra glitchy “blinds” effects. All of my video toys are unmodified as I’ve never really seen the need to get in there and mess with them to get those. The WJ-MX50 has a nice blinds effect and other cheezy stuff baked in from the factory. It’s advisable to print out the pages from the manual that lists all the wipe patterns and hang it on the wall next to the switcher; it’s got like 64 of them or something sufficiently absurd. Conspicously missing is a star wipe. (The Sony switcher shown at the top here can star wipe. If it doesn’t have a wipe you want, you can also store custom patterns in it. It also has a smoke wipe. This… uh, may or may not get used by our directors when coming out of marijuana-related news stories.)
Star wipe, and where to use it:
The wipe being accompanied by a whooshing sound amuses me far too much. The switcher at WSVN was set up with pretty much EVERY one of the weird shiny-circle-7 wipes accompanied by a whoosh. Thankfully, it was only a whoosh, and even the “NEWS ALERT” used on that station was a whoosh or a little musical bit – it was not the abrasive terrible wshEEEWWWWWWWW-CLONG!!! used by Fox News Channel.
I’m fairly sure the cheezeball Datavideo titler/switcher unit I have can do the star wipe.
Most of the Datavideo stuff I’ve seen was from the mid to late 90s. I didn’t realize they actually go waaaaaaaaaaaay back:
Datavideo’s still around and they make some really fun looking switchers and streaming production systems.
Most of my stuff is still in boxes from moving, but I’m planning to set up a nice little rack with various cheezeball video boxes and matrix switches to route video between them. Expect to see a lot of silliness come from this soon.
Seen after I emptied out its jackpot…Cyclone is a really kinda old game now, I remember first seeing them in the early 1990s. It’s still fun as heck and I can usually get the jackpot on it unless it’s been set to evil mode.There’s a hidden adjustment as to how easy it is to get that jackpot. The clock that advances the light that’s on runs at least 32 times as fast as the lights stepping around the table. The “winnability” adjustment can be set so anything from all 32 clocks all the way down to one will actually win. If it’s set particularly hard you’ll often see the game do evil things like reverse from the jackpot light you stopped it on to the one before it. It’s not subtle about the fact it’s dicking you over.When it’s not set to evil though it’s just pretty and fun to play.Speaking of games of skill… I spotted impending Rifa Madness in some video distribution amps at work.I’m using them as an excuse to get the 25 year old nightmare fuel out of there so I don’t have to fear the black burst signal being pulled out from under us. I was trying to upload an image of the waveform but the photo just won’t pass through Comcrap, so here’s an unrelated thing
Here’s a supermicro that pissed us off this week. It’s from 2015 and clearly got dumped on us as the result of a certain “text-that-gets-scrolled-on-the-bottom-of-the-news” vendor cleaning out back stock when my workplace ordered a new system.
Blaarffff. It literally seems like the bios doesn’t like certain monitors, and you have to fight it for hours to get video. You’d think with a vendor like Supermicro you’d get a board built with better parts but this thing looks like a damn Soyo. Remember Soyo? They drove themselves out of business by delivering dumpshit. This Supermicro sure looks like overpriced dumpshit complete with “hey look it’s 2001 again” capacitors.
I’ve always found the old school triax connections used for some studio cameras….. charming. Triaxial cable looks mostly like a RG-6-ish coax with another dielectric layer and another braid over it, with the end result looking a bit more like RG-11… until you see the freaking WEIRD connector it terminates into. It’s like a ginormous shell around a BNC. Trust me when I say you do not want to be coiling this cable up and have the connector fly over and smack you in the— uhhh— output spigot and terminating resistor. OW. But anyway—
Cameras hooked up by triax can be powered over the triax. To do so, the Camera Control Unit (CCU) sends a high voltage – 120-170 vdc I think, down the cable, between the outer and inner braids. A DC/DC converter inside the camera powers it and any ancillary equipment like lights hooked up to the 12v output it provides. It works great, but you MUST ensure that the voltage has been removed from the cable before unplugging it. On some systems, it seems like powering down the camera tells the CCU to stop sending that voltage (or it drops to just a few volts – just enough for it to power whatever onboard the camera tells the CCU that the cam is connected and requesting to be powered up?). Anyway— at my old station I had a few instances where someone would unplug the cable hot and it would make the camera mad or even carbon-track the plastic inside the connector.
Today I found out what happens if the cable ITSELF gets angry:
From top to bottom: The outer jacket with subtle black mark from the fault within, the middle dielectric and inner braid, and the outer braid, which frayed then burned in half at the fault location.
The ridges are from the connector’s strain relief. This fault occurred right behind the connector, where the cable was getting flexed a lot.
The CCU reported the cable was shorted out, and this was confirmed by a resistance reading of about .15 ohm at the connector on that end as measured by the onboard multimeter on a Tektronix 2236
All three elements of the cable – the center conductor, inner braid, and outer braid were shorted together.
I was able to lop off the end of the cable and remake the connector. The connectors we had in stock were circa 1996 and were made by Kings about, oh, two corporate umbrellas ago. Currently they’re under Winchester Interconnect and Winchester has no documentation on the connector including what the strip lengths are for the layers of the underlying cable. Canare and Cinch have different takes on the same thing. I managed to get it back together with new parts for the center.
The center is pretty much a crimp type BNC. Not shown, the….. ridiculous oldschool clamp thing used to hold the outer braid to the connector body, nor the giant ball-bonker connector body itself.
Not sure if it’s the world’s most perfect installation, but hey, it passed the Smoke Test and the camera’s back up on it and in service.
The pins are about 3/8″ diameter and the whole bulb is 8 1/4 inches high overall with the light output centered 5″ above the bottom. It has an average life of 300 hours. The normal application has it inside a Mr. McLargeHuge stage fresnel safely locked away behind a big thick glass lens and a metal screen. I don’t even want to think about it too hard.
For a small $945 you can get a VisionSmith ReLamp module that lets you replace it with a 275 watt LED that pays for itself *rapidly* in reduced air conditioning and power costs…