Testing, Testing

Posted in Audio, Educational, Measurements, Something Interesting, Tools on February 2nd, 2012 by RussB – 1 Comment

Crude XLR Tester

Marty has been working on a two part XLR tester, as we have been installing the panels in the transmitter rooms they had been testing with a DVM. It was suggested that a simple tone sent and received would work as a test but it’s not really. After all the work put into this new interconnect system I want to be sure every wire is connected correctly.  To that end I came up with a simple if un-wieldy device made up of two 9 Volt batteries and an XLR. With a bi-polar voltage available it’s simple to connect pin 1 to the + and – of the two batteries and then connect the Pos to Pin 3 and Neg to Pin 2, now there’s no r00m for mistakes at the other end and all three lines are tested.

But what Marty has been working on is something smaller and with it’s own lights. He used a popsicle stick to hold the LEDs (I think that was very clever) and used a AA batter pack for power in his prototype. It’s almost right but it suffers from the same fault as the RatPak I saw on-line. You can get the RatPak for about $50 and it’s a two part XLR tester that uses three LEDs. But there are several conditions that will show the same pattern of LEDs. I think thats because they use a single ended battery. To fully test you need a ground with Plus and Minus voltage, just like the audio signal thats meant to travel over a balanced audio cable.

A better one under development

I think with a little more work Marty’s system would be the best, giving you a complete readout of any fault in an XLR cable, good luck Marty.

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Getting Hot

Posted in AC Power, Broadcasting, Design, Educational, Green Energy, Heat Exchanger, Transmitters on February 2nd, 2012 by RussB – Be the first to comment

Solid State TX

Most UHF transmitter use IOT tubes to generate the high RF power levels to broadcast, these tubes are cooled by transferring a Glycol/water mix from the tube and electromagnets to a heat exchanger positioned outdoors where the mixture is passed through radiator like cooling fins with fans to blow air past them. The cooled liquid is then returned to the transmitter where the process begins again.

But some stations prefer Solid State transmitters where all RF power is generated my transistors. For low power standby/auxiliary transmitters this makes a lot of sense as the solid state transmitter will turn on and be up to full power in a matter of seconds. But compared to IOT transmitters Solid State’s are very inefficient in their AC power usage. Once you get over about 10KW of output power it’s cheaper to run an IOT transmitter when you look at the monthly utility bill.

But still some stations prefer Solid State for other factors such as no single point of failure, Solid State transmitters use lots and lots of small amplifiers to build up to the power level required. If one or even a few of these smaller amplifiers fail they remain on the air, at reduced power. And there’s no expensive IOT tube to replace every few years either.

But something they can’t get away from is heat, all transmitter generate heat and Solid State devices really don’t like it. So they require lots and lots of cooling. Most Solid State transmitters rely on air cooling where the transmitter room must become a howling, swirling, frigid air conditioned room using massive A/C units with plenty of redundancy to keep the transmitter cool.

Recently I walked into a transmitter room and found it was 104˚ F inside, it was HOT! They have a Solid State Transmitter and two

A/C unit in trouble

A/C systems  but both had failed and in the closed room the temperature has climbed all the way to 104˚.  I opened the doors to the hallway and the outside door as well. Fortunately they have large louvered openings in the back so I opened those doors as well and brought up a large 4 foot fan to help cool things off. In a short while the room was down to 90˚ and I had called the Chief  who was on the way in.

When we talked later I asked about monitoring and why no alarms had gone off, I was told they have a central monitoring facility in a nearby city but no one respond to the over temp alarm. This made me think it would be a good idea to set off an alarm now and then on purpose just to make sure that you are notified and that the monitors are awake.

Big fan in the doorway

If I was to install a Solid State transmitter today I would insist it be water cooled, it’s much more efficient and simpler to operate, they have quick disconnect water connections allowing for amplifier drawers to be pulled and re-inserted with power on. Plus you can hardly hear yourself think in the air conditioned Solid State transmitter rooms I have been in.

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The History of High Definition Television

Posted in ATSC, Books I'm Reading, DTV, Educational, FCC, People in Engineering, Television on February 2nd, 2012 by RussB – Be the first to comment

I just got a copy of a new book by Philip Cianci titled “High Definition Television” The Creation, Development and Implementation of HDTV Technology. Now thats quite a mouth full but it looks to be very interesting. Mr. Cianci covers the complete development of HD from NHKs first research back in the 60′s to how we got the HD system we now have.

I have only read part of the first chapter, so far, but if the rest of it holds to the same standard then then I expect this to be a very important and very readable book that should be on every broadcast engineer’s book shelf.

Stay tuned for more updates.

You can get the book at www.McFarlandPub.com or call 800-253-2187

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Poster Wall

Posted in Charts, Learning, Something Interesting, TheOLE.Org, Transmitters on January 26th, 2012 by RussB – Be the first to comment

I decided to put all my posters up on my Transmitter office wall, they look pretty neat, if I do say so myself.

Satellite, Analog Sync, and 3-D Video

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DTV Frequency Offset?

Posted in Analog, ATSC, Broadcasting, DTV, DTV Exciter, Educational, Engineering, FCC, Free-Over-The-Air-TV, Measurements, People in Engineering, Transmitters on January 25th, 2012 by RussB – Be the first to comment

Well that was a question for me, if you follow my blog you know that my DTV station has an frequency offset, it was required when our analog transmitter was operating and had it’s own offset, and since we were one channel above the DTV has to keep it’s distance. I had wondered about this for some time, I don’t remember at the time of analog switch off any mention of DTV channels removing their offset and even talking to the factory they informed me that no on had ever sent in their exciter to have the offset remove unless it was sent in for other servicing.

This led me to write to my friend Dane Ericksen and ask him what was what, and here is his response -

Thanks Dane

•••••••••••••••••••••••••

January 17, 2012

Russ:
We needed to check with Hossein Hashemzadeh at Media Bureau, who advises that if a DTV pilot frequency offset is specified on the station license, but the frequency offset is no longer appropriate because there is no longer a lower-adjacent full-service analog TV station within 88 km, the appropriate action is to file a Form 302 for a license modification, requesting deletion of the frequency offset.  I do not think that there is any filing fee in that case, but you should confirm this with your FCC counsel.
However, in checking the FCC records for KMTP-TV, D33 (V32), San Francisco, I do not see any provision on the station license, BLEDT-20100216ABJ, issued April 1, 2011, specifying a DTV pilot frequency offset.  Further, when I check the FCC engineering data for KMTP-TV, the “Offset:” field is blank.  Thus, I can find no evidence that the FCC records require a frequency offset, and since Section 73.622(g) of the FCC Rules is no longer applicable because all full-service analog operations in the U.S. ceased in 2009, there would appear to be no authority for KMTP-TV to be operating with a DTV pilot frequency offset.  The KMTP-TV DTV pilot frequency therefore needs to be 309.440 559 kHz ±1 kHz above the lower channel edge boundary, or 578.309 440 559 MHz, again ±1 kHz, in order to comply with the ATSC A/53 standard, and the A/54 recommended practice, as specified in Section 73.683(d) of the FCC Rules.
Regards,
Dane E. Ericksen, P.E.
Hammett & Edison, Inc.
Consulting Engineers
San Francisco, CA
707/996-5200 voice
707/996-5280 fax
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A Little Story about Car Radios

Posted in Learning, People in Engineering, Something Interesting, TheOLE.Org on January 25th, 2012 by RussB – Be the first to comment

A friend of mine sent this to me and I thought it was very interesting to see where companies and devices we know came from. If you know who wrote this story please let me know so that I can put their name to it.

••••••••••••••••••••••••

Bill

Radios are so much a part of the driving experience, it seems like cars have always had them. But they didn’t. Here’s the story.

Sundown

One evening in 1929 two young men named William Lear and Elmer Wavering drove their girlfriends to a lookout point high above the Mississippi River town of Quincy, Illinois, to watch the sunset. It was a romantic night to be sure, but one of the women observed that it would be even nicer if they could listen to music in the car.

Lear and Wavering liked the idea. Both men had tinkered with radios Lear had served as a radio operator in the U. S. Navy during World War I , and it wasn’t long before they were taking apart a home radio and trying to get it to work in a car. But it wasn’t as easy as it sounds: automobiles have ignition switches, generators, spark plugs, and other electrical equipment that generate noisy static interference, making it nearly impossible to listen to the radio when the engine was running.

Signing On

One by one, Lear and Wavering identified and eliminated each source of electrical interference. When they finally got their radio to work, they took it to a radio convention in Chicago . There they met Paul Galvin, owner of Galvin Manufacturing Corporation. He made a product called a battery eliminator a device that allowed battery-powered radios to run on household AC current. But as more homes were wired for electricity, more radio manufacturers made AC-powered radios. Galvin needed a new product to manufacture. When he met Lear and Wavering at the radio convention, he found it.

He believed that mass-produced, affordable car radios had the potential to become a huge business.

Elmer

Lear and Wavering set up shop in Galvin’s factory, and when they perfected their first radio, they installed it in his Studebaker. Then Galvin went to a local banker to apply for a loan. Thinking it might sweeten the deal, he had his men install a radio in the banker’s Packard. Good idea, but it didn’t work , half an hour after the installation, the banker’s Packard caught on fire. (They didn’t get the loan.) Galvin didn’t give up. He drove his Studebaker nearly 800 miles to Atlantic City to show off the radio at the 1930 Radio Manufacturers Association convention. Too broke to afford a booth, he parked the car outside the convention hall and cranked up the radio so that passing conventioneers could hear it. That idea worked, he got enough orders to put the radio into production.

What’s In A Name

That first production model was called the 5T71. Galvin decided he needed to come up with something a little catchier. In those days many companies in the phonograph and radio businesses used the suffix œola for their names Radiola, Columbiola, and Victrola were three of the biggest. Galvin decided to do the same thing, and since his radio was intended for use in a motor vehicle, he decided to call it the Motorola.

But even with the name change, the radio still had problems:

When Motorola went on sale in 1930, it cost about $110 uninstalled, at a time when you could buy a brand-new car for $650, and the country was sliding into the Great Depression. (By that measure, a radio for a new car would cost about $3,000 today.) In 1930 it took two men several days to put in a car radio, the dashboard had to be taken apart so that the receiver and a single speaker could be installed, and the ceiling had to be cut open to install the antenna.  These early radios ran on their own batteries, not on the car battery, so holes had to be cut into the floorboard to accommodate them. The installation manual had eight complete diagrams and 28 pages of instructions.

Hit The Road

Selling complicated car radios that cost 20 percent of the price of a brand-new car wouldn’t have been easy in the best of times, let alone during the Great Depression , Galvin lost money in 1930 and struggled for a couple of years after that. But things picked up in 1933 when Ford began offering Motorola’s pre-installed at the factory. In 1934 they got another boost when Galvin struck a deal with B. F. Goodrich tire company to sell and install them in its chain of tire stores. By then the price of the radio, installation included, had dropped to $55. The Motorola car radio was off and running. (The name of the company would be officially changed from Galvin Manufacturing to Motorola in 1947.) In the meantime, Galvin continued to develop new uses for car radios. In 1936, the same year that it introduced push-button tuning, it also introduced the Motorola Police Cruiser, a standard car radio that was factory preset to a single frequency to pick up police broadcasts. In 1940 he developed with the first handheld two-way radio, the Walkie-Talkie (or was it Handie-Talkie), for the U. S. Army.

A lot of the communications technologies that we take for granted today were born in Motorola labs in the years that followed World War II. In 1947 they came out with the first television to sell under $200. In 1956 the company introduced the world’s first pager; in 1969 it supplied the radio and television equipment that was used to televise Neil Armstrong’s first steps on the Moon. In 1973 it invented the world’s first handheld cellular phone. Today Motorola is one of the second-largest cell phone manufacturer in the world. And it all started with the car radio.

Whatever Happened To Them

The two men who installed the first radio in Paul Galvin’s car, Elmer Wavering and William Lear, ended up taking very different paths in life. Wavering stayed with Motorola. In the 1950′s he helped change the automobile experience again when he developed the first automotive alternator, replacing inefficient and unreliable generators. The invention lead to such luxuries as power windows, power seats, and, eventually, air-conditioning.

Lear also continued inventing. He holds more than 150 patents. Remember eight-track tape players? Lear invented that. But what he’s really famous for are his contributions to the field of aviation. He invented radio direction finders for planes, aided in the invention of the autopilot, designed the first fully automatic aircraft landing system, and in 1963 introduced his most famous invention of all, the Lear Jet, the world’s first mass-produced, affordable business jet. (Not bad for a guy who dropped out of school after the eighth grade.)

Some of us have been fortunate to have met both of these gentlemen and they were – gentlemen.

 

 

 

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We’re Back to Full Power!!!!!

Posted in ATSC, Broadcasting, DTV, DTV Exciter, Measurements, Transmitters on January 24th, 2012 by RussB – Be the first to comment

Back to 100%

Well I did it, my TX is back to full power, it’s about time. I had been tracking the power from the Exciter out, the IPAs out and the IOT out but so far they all tracked one another. So I decided to run the exciter power up and down and see how they tracked then. So I hooked up my PC laptop and started up the ADAP software and plugged the serial port into the DB9 on the front of the exciter. I started running power up, we were at about 70%. Nothing changed, so I ran power down, maybe I was at an upper limit. Again no change, it’s not good when your exciter does not respond to your commands.

So now I jump the power down, you can do that by entering a number much lower than the power level you’re at. It

The Setup with R&S and PC

responds, power drops to about 40%, okay, now we’re getting somewhere. So I note the levels and try raising power. No go. We’re making power and pictures but the exciter is acting strange, and then I remember. A few times in the past I had to reboot the exciter, not this one and it was several years ago. I don’t think there’s any Windows anything in the exciter, at least I hope not.

A readout from the Exciter

I punch the Beam Mode button, which kills the RF and go around the back the turn off the exciter. I walked to the office and back to kill time and turned it back on. I gave it a couple of minutes and hit the RF mode button. Power came up, way up, to 110%. I backed it off to 100%. Don’t know what happened, It was not in AGC mode but I know AGC needs adjustment and I will do that as soon as I have time. Plus that would not explain why power dropped all of a sudden.

I go next door to borrow the R&S ETL so I can run the corrections. When I hook it up to the Mask Filter output I have to kill all the monitors as that’s the same feed. The eye pattern looks pretty bad. Now I have a little cheat sheet I use       to

Never saw one like this before

remind me what corrections I should run in what order and I proceed with it. But it does not go like I expect it to, I never saw the constellation display showing double lines on several of the levels, so in frustration I turn to the instruction manual. Who knew that Thomson had a whole procedure for running the corrections on this exciter?

My tweakers

So for the first time ever I follow directions. It has me check the Feedback level, which is good and then a few more things until I get to one that is way our from the reading they want. So I follow directions and run the list of corrections it tells me to. What do you know, the constellation cleans right up, it looks textbook perfect. My MER is 35.1dB, which if you don’t know, is really, really great. Every time I leave the room and come back I expect power to have dropped, but it’s still good. I hope it’s that way when I get in tomorrow morning. Wish me luck.

 

 

 

 

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A Reboot or Two

Posted in AC Power, Broadcasting, High Voltage, Transmitters on January 24th, 2012 by RussB – Be the first to comment

Carbon covers the inside of this breaker

My friend’s transmitter was experiencing random Crowbar events and he was looking for an answer, at first he found a loose 40Ω power resister in the High Voltage. Nope, then he checked his main HVPS breaker and found it was shot. The contacts were all burned off and it was covered in soot. A new one from the manufacture cost about $2000 but from a supplier it was closer to 1/4 of that. The problem is that these types of breakers have all kinds of settings and configurations and buying it on your own may not get you what you need to work in the transmitter. It’s best to bite the bullet and get what you need.

Anyway, he got the right one, and put it in, let the tube warm up and put high voltage to it and BAM! Crowbar, he tries several more times each

The breaker in parts

ending with a BAM! He asked me about it and I told him that in my experience (at one time I had six IOT transmitters under my care) once an IOT has been off it can be very cranky, and will crowbar several times before staying up. So he tries some more and gets it to stay up, but now he has no RF. It looks like his IPA is off but the breaker is on and he can see on the LCD readout that there’s voltage to the IPAs. I have to get back to my own TX and perform my own miracle on my TX, more later.

When I come back I see he has RF and I ask him how he did it, he tells me that the controller showed a fault after the crowbars and he had not cleared it because it’s just an indicator. No it’s not he says, the fault kept the IPAs off, resetting it brought power back. He’s been working with transmitter for several decades and these Harris transmitters for the last several years and he had never encounter this before. But he was happy to have power back and was going to let this TX run into the dummy load over night to see how well it runs.

To learn more about Crowbars watch my video that tells you all about them here.

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Posters from TheOLE

Posted in 3D, Broadcasting, Charts, Measurements, Satellite, TheOLE.Org, Time/Timing, Video on January 24th, 2012 by RussB – Be the first to comment

I just updated our North American Broadcaster’s Satellite Chart, I got a couple of orders and I like to make sure they are up to date. For those of you not familiar with TheOLE charts we have the afore mentioned Satellite chart and an Analog NTSC Sync Chart and the 3-D Video Chart that shows the different transmission formats as well as the different display systems and camera setup used in 3-D video.

I am currently working on ASI and 8-VSB Charts.

Here they are the current charts for you to check out. The large version is only $12 including S&H and is 3 feet by 2 feet and if you ask I will put your station name right on the chart. You can also get the mini Charts, 3 for $5 including S&H. Click here to order.

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Failed Microwave Link – Cause Found – Acorns!

Posted in Antenna, Broadcasting, Educational, Engineering, RF Microwave on January 21st, 2012 by RussB – 1 Comment

This is a video from YouTube that shows what happens when mother nature runs amuck. I was told a story recently about another microwave link that kept failing, it seems that a bird would store it’s food in the feed horn of the microwave dish. It had pecked a hole through the thin plastic cover and shoved the food inside till it blocked the signal. This went on until the smart engineer placed a 1/4″ thick piece of plastic over the feed horn.

 

Here is the video -

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