karn (10/25/82)
I have learned a good deal about this topic, because I have been both the generator and the victim of computer RFI. I am an active amateur radio operator interested in computers, and as such have torn my hair out many times when trying to use my home computer in persuit of my hobby, especially when receiving very weak signals from satellites. Anyway, the rules are like this: All new computer equipment manufactured after a certain date (I don't know exactly when offhand) must be certified by the manufacturer as complying with either "Class A" or "Class B" emission limits. A device intended for a commercial environment (a VAX, for example) will have to meet Class A. Class B requirements, which are MORE strict, will have to be met by computing devices intended for residential environments (games, personal computers, etc). The FCC allows uncertified equipment to be manufactured up to the deadline, but requires a warning notice to be placed on the equipment that says, in effect, that the equipment may cause interference if used in a residential area and that the owner would be required to take whatever steps are necessary to correct any interference. For a sample of this notice, look in those little plastic pockets on the back door of any VAX made in the last two years or so. Many newer terminals are coming out that are certified as meeting either the Class A or B RFI limits. My home terminal, the Heath H-19A, meets the B limits. It can be operated ten feet away from a TV with rabbit ears and not generate any RFI. Unfortunately, retrofitting earlier terminals to make them RFI tight is much more difficult than designing it into the terminal to begin with. It has ALWAYS been the case that the owner of any device (whether intended to be a radio transmitter or not) that interferes with another service by radiating energy within the frequencies assigned to the other service has the legal responsibility to correct the problem. You'd be amazed at the variety of non-communications devices that can radiate objectionable amounts of RF: computers, terminals, power lines, oil burners, microwave ovens, electric motors, etc. This is not to be confused with interference caused by the inability of a device to reject authorized transmissions to which it isn't supposed to respond, e.g., a record player that picks up a local amateur radio transmitter. President Reagan recently signed a bill that gives the FCC to set rules requiring the manufacturers of home entertainment electronics meet certain minimal standards for the rejection of out-of-band RF energy. Hope this helps. Phil Karn, KA9Q BTL Murray Hill
jcwinterton (11/01/82)
Just a side note in this. This week, I noticed that my ti59 calculator radiated quite a lot of static on the AM broadcast radio band. Holy cow, doesn't anyone shield anything? John Winterton.
ignatz (11/01/82)
Golly, mentioning the TI calculator interference brings back memories. Surely I'm not the only one who remembers that the HP-35 would affect an AM radio on a per-keystroke basis? This little beast actually produced 'notes' that were clean enough to play tunes. My HP-45 did this as well, but the tones were not discrete enough to play tunes. However, you could--and I did--use this to tell when a program was done! While running a program, you also had an increase in generated noise; when the program was done, the output level went down. I could even tell when it was in loops... Incidentally, this was never resolved to my satisfaction, but I think the EE's said they thought that the calculator was affecting the IF, not the primary frequencies... ~a ~v (sheesh.) Dave Ihnat ihuxx!ignatz
wagner (11/02/82)
Airlines typically get very upset about people generating RFI onboard planes (dont turn on your CB radio) - I wonder how they feel about calculators like John Wintertons or the new several-megahertz pocket micros? Michael Wagner, UTCS
wagner (11/03/82)
Our 370/165 used to play tunes in the short wave band. We used to listen to it sometimes at night while we were making coffee. You could tell when the assembly was finished and the machine was idling by the change in the roughness (not the frequency) of the note it played. Strange what amuses small minds late at night while benchmarking. Michael Wagner, UTCS
doehring (11/03/82)
Don't forget that a while back ( and maybe still ) you were NOT ALLOWED to use hand held calculators on board a commercial airline, since the RFI emitted interferred with the NAVIGATION equipment, I guess that this is one way to hijack an airplane.... Martin S. Doehring decvax!yale-comix!doehring doehring@YALE
dmmartindale (11/03/82)
I read of a case not long ago where an airliner at cruising altitude lost all VHF voice communications with the ground. When flying IFR, this is quite serious, even if enough of their navigation gear was still working so that they knew where they were. The culprit turned out to be one of the passengers playing one of those pocket electronic games.
jim (11/03/82)
My first computer was an IBM 1130, in about 1968, and the thing that impressed me most about it was that they had a program which would play "The Stars and Stripes Forever" through any nearby AM radio. It worked by running various timing loops -- the longer the loop, the longer it took to execute and the lower the pitch of the resulting tone. It made such an impression that I decided to make computers my life's work.
tjr (11/03/82)
At the University of Illinois physics computer (circa 1971), we had an IBM 7094. One of the operators (who often worked the nearly-idle night shift) wrote a "music compiler", which used accumulator loops with varying increments to play tunes through an ordinary AM radio placed on the console. He had the capability for 3-note chords, arbitrary rhythms, etc. The compiler was written in FORTRAN. The most spectacular piece of computer music I have ever heard was his version of the 1812 Overture. It lasted about 6 minutes, and included squealing tape-drives for the carillons, and massive overprintings on the printer for cannons. Synthesizer-music just can't come close to the bald incongruity of this crazy computer playing Tchaikovsky! Tom Roberts ..ihps3!ihnet!tjr
terryl (11/03/82)
Well, when I first started programming, I knew a person who programmed an IBM 1130(gasp! How archaic) to play music by running a program and placing an ordinary AM radio on the console. The sound was something you had to hear to appreciate!!!!
henry (11/03/82)
Best be very careful about causing interference with aircraft navigation or communications. This is one area where the feds will jump on you with both feet, *regardless* of whose equipment is technically to blame.
leichter (11/04/82)
Well, since all the old tales are coming out...back on the ol' IBM 1620, you could generate reasonably clean notes on a nearby AM radio with carefully built loops. I heard a couple of "concerts" done this way. It got pretty popular at one point, and the SHARE catalogue for the 1620 listed a number of "music compilers". One of the most sophisticated, called something like "Maestro", understood standard musical notation (in some "linearized" format) including repeats. It generated a program that played the music, accompanying itself on the paper tape punch for percussion! And then there was "printer music". I only heard this once. On some model printer or other (IBM) a number of years back, with careful selection of the stuff you were printing, you could get notes out of the rubbing of the chain against the paper, or something. Again, there were compilers. 'Twas impressive nor for the quality but that it was done at all! -- Jerry decvax!yale-comix!leichter leichter@yale
bcw (11/04/82)
From: Bruce C. Wright @ Duke University Re: Computer music I've heard of several things like this done; on the Sigma V which we used to have at the Duke Medical Center, there was a programmable audio alarm which was used by someone (I think from the user's group, it wasn't locally) to write "music" - it too had something of a "music compiler" which was based on the macro assembler. The only thing I remember for it was a medley of popular tunes which ran for maybe 10 minutes. Some of the people at XDS reportedly tied the audio alarm to the crash routine in the system to produce "a 20-second descending whistle," but unfortunately I never heard or saw that one except by reputation. Also, there was a program on one of the old IBM-1130 computers which would use the line printer (printing lines of different characters which had a different pitch for each type of character) which played "Anchors Aweigh" (I think it was written locally by one of the computer freak types who may be listening in on this - I don't think I'll embarrass him by giving names). Bruce C. Wright @ Duke University
wagner (11/04/82)
HMMMM ... I thought there was a way of taking your OSBORNE on the plane and using it (a battery option or something). I guess they wouldnt appreciate that! Michael Wagner, UTCS
david@sri-unix (11/04/82)
I realize that this can't compare with IBM machines playing the 1812 Overture, but I used to work with Nicolet Zeta pen plotters, and we had a diamond-shape test pattern that just by chance generated an (almost) scale - something to do with varying the distance of wher the pen carriage was on the wire. David Brown Varian
jdd (11/04/82)
Well, when \I/ first started programming, we had an IBM 7040 that
could play tunes over the radio \and/ an IBM 1401 that could play
tunes on its line printer. Alas, although they shared an I/O
channel, they couldn't play duets!
Cheers,
John ("I never sign my middle name") DeTreville
Bell ("Information Age") Labs, Murray Hillrcf (11/04/82)
The 1401 could also play tunes on the radio, as I heard with my own ears -- Now if someone had just had it play the line printer and the radio at the same time ... Robert Field Qume, San Jose
pcmcgeer (11/04/82)
With justification. If a pilot's radio goes out when he is in a PCZ or a VTA he and his aircraft are in big trouble. Forget the feds: the pilot will jump on you with both feet, and, left to himself, would toss you out at 35,000. Rick.
lsk (11/05/82)
In college we had a program that turned the computer console into a piano keyboard! Of course, we only allowed the talented operatorts to play tunes (you can only stand so much chopsticks). We had an IBM 360/44 and the radio had to go somewhere on the top of the CPU, as I recall. Speaking of the 360/44; did anyone else use/know of them? We were told it was a machine IBM usually marketed in EUROPE and that our having mit made us unique? WOnder if that was bull? 'Course, they never told us how WE got one!!! Larry S. Kaufman , Western Electric Co, Network SOftware Center, Lisle, IL
tbm (11/06/82)
How well I remember the HP2100 playing music on a card stuck in the paper tape reader. Love to listen to it and adjust the card to change the 'fi' (as in HiFi). Tom Merrick
davy (11/06/82)
#R:eagle:-57300:pur-ee:4500004:000:345 pur-ee!davy Nov 5 10:44:00 1982 Someone told me a story about a guy who found out you could make "music" by having the line printer print various characters..... He slept something off so it would run about 3:00 in the morning, the poor operator on duty at that time suddenly became aware of his printer playing "The Halls of Montezuma"..... --Dave Curry pur-ee!davy
goutal (01/04/83)
Catching up on 'old news'... Note that there used to be a program for the PDP-12 (and -8, too) that would produce AM music you could listen to on a nearby AM radio. I'm sure other machines had such programs. (Yes, this is getting far afield from RFI and *terminals*). Today, I believe, the FCC frowns on this sort of thing. Sigh. The -12 also had a speaker (!) connected to the link (carry) bit, for some reason or other, and it turned out mighty handy for the same reason as the fellow mentioned about his HP-45 -- tracking the progress of one's program (of course, there were front panels in those days, too, that told you a lot). Moving back into the realm of possibly dangerous, or at least noxious, radiation... Does anyone remember working with the old Data General machines (circa 1973... maybe even still!)? For those of you who don't, I remember being able to tell what stage of compiling or linking my program had gotten to, simply from the whine of the power supply. And I don't mean that ours was in bad repair; it was the normal behaviour of the 8xx and 12xx Nova series, due, I believe, to the use of switching- type power supplies (I may have this a bit adrift... it's been a while since I understood much about hardware) -- the effect was similar to the flyback whine in some (especially older) TV's. Note that this was not just *faint*, either! I could do that trick of telling what it was doing from several offices down the hall! Anyhow, it used to give me a headache, and I took to wearing airport- type silencing muffs. Amazing the lengths some companies will go to to compete! -- Kenn (decvax!)goutal
goutal (01/04/83)
Another late entry, this time about using an OSBORNE on an airplane. (Hope this isn't a repeat.) Recently, in HUMANETTES or TELECOM or someplace, an article was posted about how some company was planning to supply airlines with in-flight data-terminal service for passengers. Either they found a way to beat the rap, or we're gonna see a lot of planes coming down in unexpected places! -- Kenn (decvax!)goutal