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Brief Update

All is well in Engineering Radio Land, just very busy with typical projects. Nothing really note worthy, but there are some interesting things in the pipe line, which will be posted once those projects begin. Regarding myself, Hockey Season is in full swing.

Ruined shot on goal

My son (in blue) messing up somebody’s shot on goal. Good stuff.

I received an interesting question from occasional reader Gary over the weekend:

Have you ever heard of, or looked into, the “Max Headroom incident”?

Yes, I have heard of it, but never really thought about it that much. At that time, I was in California getting ready to ship out to Guam. I remember some brief news reports on it when it happened. After some reflection, I sent along this reply:

Good question. I have done a little bit of work at TV stations from time to time. In the mid to late 80’s, most television stations used 6 GHz analog microwave links between their studios and transmitters. These where unencrypted. Most often, these links used Microwave Associates gear, which had transmitter power output of about 3 watts into a rectangular wave guide. That was coupled, via elliptical wave guide into a 24 or 36 inch parabolic antenna. As you know, parabolic antennas have a main lobe and side lobes in their radiation pattern. The smaller the dish size, the broader the main lobe is and the further out the side lobes are. Since the Chicago studio to transmitter path was fairly short, I’d hazard a guess that they where using 24 inch antennas. In major markets, there was often a backup STL system on a different frequency (as the Wikipedia article indicates). Later on, most stations had a third backup via the cable company using either directly fed coax or fiber optic cable.

Since cutting into the transmission line of the microwave link at either side of the system would almost certainly fail, what I think happened is the perpetrators discovered (easy to do) the frequency of the 6 GHz link and over powered the normal signal at the receive antenna. This is possible if they used a much larger antenna and where located in either the main lobe or a side lobe of the receive antenna. If you recall, in the late 80’s C band satellite dishes where very popular. It would not be too difficult to repurpose one of these dishes for a 6 GHz antenna. Most C band dishes where 5-6 feet in diameter, which would give them much more gain than a 2 foot dish. They simply would have had to figure out a way to feed the dish with elliptical wave guide and adjust the focal length for 6 GHz. I’d bet there where dozens of C band dishes on Chicago roof tops.

Anyway, that is my theory.

I watched a few youtube clips of the event. The fact the video was noisy indicates some type of co-channel interference. I think there was no audio because they guessed the microwave audio subcarrier frequency wrong the first time. The second incident, there was audio. Whoever did to this had to have pretty good knowledge of television STL system. Wikipedia article here: https://en.wikipedia.org/wiki/Max_Headroom_broadcast_signal_intrusion

What do you guys think?

In other news, I have begun messing around with a few ideas on single ended tube audio amps and contemplating a DIY tapered transmission line speaker build. Actually, there is some pretty interesting software out there for speaker design which would be fun to play with.

I have also been messing about with room EQ Wizard, which I think I will do a separate post on.

That is all from here, hope that all of you are well.

Look at my wonderful tubes!

I found this promotional picture in an old NAB conference technical papers book dating to 1969:

RCA TT-30FL promotional picture

RCA TT-30FL promotional picture

So here we see an obviously qualified and appropriately dressed technician gesturing to all the components she is about to install in the transmitter behind her. I wish I worked there.  No, wait, I wish I had that transmitter and perhaps this fetching young woman would come and work at my station.  Well, hell, I don’t need a TV transmitter, just the woman.

Sigh.

I wonder how many of these rigs RCA sold before the broadcast division went out of business.

By way of reference, the RCA TT-30FL is a VHF television transmitter, 30 KW peak visual power, 7.5 KW peak audio power, air cooled.

What passes for news these days:

Without further comment, via The Onion:

The often misquoted Hunter S. Thompson

I have often heard or read this Hunter S. Thompson piece misquoted as “The Radio business is uglier than most things…”  After a bit of research, I found this directly from his book called Generation of Swine: Tales of Shame and Degradation in the ’80s (New York: Summit Books, 1988):

The TV business is uglier than most things. It is normally perceived as some kind of cruel and shallow money trench through the heart of the journalism industry, a long plastic hallway where thieves and pimps run free and good men die like dogs, for no good reason.

Phew, thank God I don’t work in TV, that must be really bad.

Axiom


A pessimist sees the glass as half empty. An optimist sees the glass as half full. The engineer sees the glass as twice the size it needs to be.

Congress shall make no law respecting an establishment of religion, or prohibiting the free exercise thereof; or abridging the freedom of speech, or of the press; or the right of the people peaceably to assemble, and to petition the Government for a redress of grievances.
~1st amendment to the United States Constitution

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.
~Benjamin Franklin

The individual has always had to struggle to keep from being overwhelmed by the tribe. To be your own man is hard business. If you try it, you will be lonely often, and sometimes frightened. But no price is too high to pay for the privilege of owning yourself.
~Rudyard Kipling

Everyone has the right to freedom of opinion and expression; this right includes the freedom to hold opinions without interference and to seek, receive and impart information and ideas through any media and regardless of frontiers
~Universal Declaration Of Human Rights, Article 19

...radio was discovered, and not invented, and that these frequencies and principles were always in existence long before man was aware of them. Therefore, no one owns them. They are there as free as sunlight, which is a higher frequency form of the same energy.
~Alan Weiner

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