Symmetric vs. asymmetric radio service

I can't Google for this -- I just tried.

Broadcast radio, and DirectLink satellite TV, have Really Expensive transmitters to serve lots and lots of cheap receivers, because it minimizes total system cost.

"Old style" satellite TV had (fairly) inexpensive transmitters and (until people put them in their back yards) a few big expensive receivers (and antennas). Because -- it minimizes total system cost (at least until everyone put one in the back yard).

Is there a name for this sort of economic decision? I'm trying to write some material for training new engineers, to give them an idea of how decisions like this are made.

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Tim Wescott 
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Tim Wescott
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Upfront v. recurring?

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Rob Gaddi, Highland Technology -- www.highlandtechnology.com
 
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Rob Gaddi

There is also the "ricochet" network, where nodes pass packets to their destination.

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John Larkin         Highland Technology, Inc 
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John Larkin

Technology is mainly what changed that. The transmitters have a hell of alo t more power, and I bet by just using the diameter of the receiver dish it can be mathematically calculated.

As far as I can tell, the old big six foot satellite dishes picked up signa ls from Sputniks (my pet name for them) that were doing alot more things. L ike handling overseas phone calls and all kinds of shit. But now, they have better solar cells and dedicated satellites that do noting but television.

I was there when only the few had a dish, and it was huge. And it only used SSAVI scrambling which I found quite easy to beat. Then for security the d igitally encoded the audio but then some people didn't care. We used to wat ch football games with the TV sound down and the radio on, and the announce rs were way better because they assumed you could not see it. Bars were doi ng that and nobody tured them in even though it was a $250,000 fine.

Since that was also unenforceable they invented BMAC and that is when they won the war. They started using that encoding and you could buy a board to beat it, for $11,000. That made it worth it to just pay for it. It was chea per to pay for it.

Things have of course gone way past that now, the system is unbeatable exce pt for the very few who have a very high skill level and inside knowledge. Used to be there were cheater "smart cards" but I haven't heard of them for a while. They sold them, not linked to an account but now if they are not linked to an account they don't work. And the encoding is ridiculous. Recei ve the signal and it looks like noise, it takes specific information even t o sync to it.

I know most of my shit here is historical, but it still comes down to money . The digital age is here, they don't want it so you can just tune in a fre quency and even make a phone call. Remember dialtone theft ? When you had 4

6/49 Mhz cordless phones people would come up your driveway and call their relatives in Cube or Nigeria or some other east bumfuck. you get the bill. Then they put in a digital circuit to require a "handshake" for the base to operate.

Two things happened. they now have dedicated Sputniks with alot better batt eries and alot more power and I bet they are semi-directional to just cover a certain area and they got another one for another area. Plus I was ridin g with my ex-boss one day and saw two dishes on one house, which in and of itself it not that unusual, but they were pointed different directions. I a sked him if what was up with that. He said one of them is the Arab network. I didn't realize they still did that but I have noticed some censoring of the news, like taking stations off that the people actually want for altern ative news sources. Cable companies do it as well.

In the old days you had motors to move the dish to pick up a different Sput nik, but they are all fixed now. them days are over. Also, in the old days I lived in Lakewood, Ohio and we had an RCA TV with the CTC25 chassis with a nuvistor in the tuner RF stage. I used to watch CFPL from Canada, and I kinda liked watching their news. Well with digital TV them days are over. T hey got nowwhere near the range. Control of information.

If you don't want to put the political aspects of all this in your material fine, but I thought I would mention it.

Reply to
jurb6006

Hmm OK I get what you mean, but I want a different example. (I'm not sure your's fits the mold) Big old satellite dishes were ~$3k, new small dishes are ~$300. Some of that savings is in the size and some in the number of units.

Were old satellite transmitters that much cheaper than newer ones?

Maybe compare trains and cars for people transport?

George H.

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George Herold

I'm not sure I follow your satellite TV example, since the earth station expense for U/L and D/L didn't differ that much with the big sites, i.e., the TX wasn't necessarily cheaper than the RX and was probably more expensive.

Cellular systems are comparable, though; e.g., handsets are way cheaper than basestations, by many orders of magnitude. So are cable systems and many similar systems.

The term "big stick" gets used sometimes in these contexts to refer to a large, expensive central antenna or tower, such as for a broadcast TV/Radio transmitter.

I think the terms you used in the title are appropriate. They do apply to and are often used to describe the channel usage as well; e.g., many systems have much more bandwidth and data capacity in the downstream direction than upstream, especially as experienced by a single user terminal, so the term "asymmetric" is often applied, especially if the user terminal uses a different bandwidth, channel, or waveform than the provider. So, since "asymmetric" is used to describe the channels, physical layers, throughput, etc., I don't know why it wouldn't be appropriate to also apply it to the terminal economics.

Reply to
Eric Jacobsen

One of the other things that changed in the meantime was the ability to make very much higher sensitivity LNB front ends for the receivers.

The available power on a satellite is limited. Modern satellites try hard only to illuminate the are they served. Earlier ones less focussed.

ADSL would be one obvious example where most people spend a lot more of their time downloading data than uploading it.

Regards, Martin Brown

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Martin Brown

A C-band uplink was around a half million dollars, in the early '80s. You can find some of the history online in old issues of Broadcast Magazine, and the CATV Journal.

One of the big things that allowed the use of smaller dishes was higher powered transponders in the satellites. The other was improved noise figure in the LNA/LNB/LNC. Early LNAs required 120 VAC to the dish to power it. The original installs ran the 4 GHz signal to the receiver through pressurized Heliax. That was followed by a microwave power divider, if there were more than one receiver on that polarity. A second set of LANa, Heliax and divider was needed, if you needed both polarities. A typical receiver was the Rockwell/Collins SVR-4F fixed tuned Receiver which sold for over $4,000 in 1980. A few years later, the Microdyne 1100 LPR sold for $1200. It was agile, and had two RF inputs. The output was a lot cleaner than the SVR-4F, or the cadillac of the industry, the Scientific Atlanta 6600 series.

BTW, the uplink used by Captain Video to jam HBO is abandoned, and a few miles from here. After that incident, HBO purchased some high power amplifiers to boost the output, if another attempt was made. What most people don't know, the transponders have a fixed gain, so the uplink power determined the output level. It was selected to serve the desired footprint, and no more. Excessive power levels reduced the stored power in the satellite's battery. Since there were up to 24 transponders in use, it affected everyone. The second generation of satellites what were built strictly for cable TV were higher power, and had several spare TWTs that could be remotely switched in when a transponder failed. That was the Galaxy series. Prior to that, they had to buy or rent spare transponders on telephone or broadcast satellites. These were typically older birds that were near EOL, and the transponders were already degraded. The motto in the cable industy was "A TWT on earth was worth $1000, in orbit it was with $1,000,000."

BTW, I still have manuals for the Rockwell and S/A receivers I mentioned above. I used to repair them, in the '80.

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Michael A. Terrell

Huh, never heard of Captain video... or Captain Midnight.

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George H.

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George Herold

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