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Altair / Fool on the Hill question

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  • Evan Koblentz
    Altair experts, You all know about the famous Fool on the Hill demo. Bill Deg. demo d it a couple of VCF Easts ago. InfoAge, at this year s Philadelphia
    Message 1 of 21 , Mar 28, 2013
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      Altair experts,

      You all know about the famous "Fool on the Hill" demo. Bill Deg. demo'd it a couple of VCF Easts ago.

      InfoAge, at this year's Philadelphia Science Festival (April 20), is doing a "how radio works" theme. It was suggested that maybe MARCH could participate by doing the Altair demo several times during the day.

      I like that idea! But I wonder: with a bunch of radio gear operating in very close proximity, will the demo still work, or will there be too much interference for it to operate correctly?
    • Dave McGuire
      ... It s not at all likely that the radio stuff will interfere with the Altair. It is likely, however, that the Altair will interfere with the radio stuff,
      Message 2 of 21 , Mar 28, 2013
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        On 03/28/2013 11:20 PM, Evan Koblentz wrote:
        > You all know about the famous "Fool on the Hill" demo. Bill Deg. demo'd it
        > a couple of VCF Easts ago.
        >
        > InfoAge, at this year's Philadelphia Science Festival (April 20), is doing
        > a "how radio works" theme. It was suggested that maybe MARCH could
        > participate by doing the Altair demo several times during the day.
        >
        > I like that idea! But I wonder: with a bunch of radio gear operating in
        > very close proximity, will the demo still work, or will there be too much
        > interference for it to operate correctly?

        It's not at all likely that the radio stuff will interfere with the Altair.
        It is likely, however, that the Altair will interfere with the radio stuff,
        especially if the radio stuff is below 30MHz or so.

        -Dave

        --
        Dave McGuire, AK4HZ
        New Kensington, PA
      • Kyle Owen
        ... Nah, only if you put a big ole Yagi on it! :) Hey, at least it doesn t have a switching supply built in. Those are the worst! The university s ham club
        Message 3 of 21 , Mar 28, 2013
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          On Thu, Mar 28, 2013 at 10:30 PM, Dave McGuire <Mcguire@...> wrote:
           

          On 03/28/2013 11:20 PM, Evan Koblentz wrote:
          > You all know about the famous "Fool on the Hill" demo. Bill Deg. demo'd it
          > a couple of VCF Easts ago.
          >
          > InfoAge, at this year's Philadelphia Science Festival (April 20), is doing
          > a "how radio works" theme. It was suggested that maybe MARCH could
          > participate by doing the Altair demo several times during the day.
          >
          > I like that idea! But I wonder: with a bunch of radio gear operating in
          > very close proximity, will the demo still work, or will there be too much
          > interference for it to operate correctly?

          It's not at all likely that the radio stuff will interfere with the Altair.
          It is likely, however, that the Altair will interfere with the radio stuff,
          especially if the radio stuff is below 30MHz or so.

          Nah, only if you put a big 'ole Yagi on it! :) Hey, at least it doesn't have a switching supply built in. Those are the worst! The university's ham club shack is almost unusable since the whole building is generating an untold amount of RF noise from all of the computers.

          I'm about to give a ham radio demo to the AM radio lab at my university on the 1st. If I had a working Altair, I would definitely bring that. But in lieu of an Altair, I'm bringing a Raspberry Pi, which apparently makes for an excellent FM transmitter on 100 MHz. Haven't played with it yet, but I've seen the YouTube video of it working. Good luck with the demo; that should be a lot fun!

          73,

          Kyle
        • joshbensadon
          ... I think the RFI is at the IF level (455khz), if this is the case, then the other exhibits shouldn t interfere with the demo. Another radio in close
          Message 4 of 21 , Mar 28, 2013
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            --- In midatlanticretro@yahoogroups.com, "Evan Koblentz" <evan@...> wrote:
            >
            > Altair experts,
            >
            > You all know about the famous "Fool on the Hill" demo. Bill Deg. demo'd it a couple of VCF Easts ago.
            >
            > InfoAge, at this year's Philadelphia Science Festival (April 20), is doing a "how radio works" theme. It was suggested that maybe MARCH could participate by doing the Altair demo several times during the day.
            >
            > I like that idea! But I wonder: with a bunch of radio gear operating in very close proximity, will the demo still work, or will there be too much interference for it to operate correctly?
            >

            I think the RFI is at the IF level (455khz), if this is the case, then the other exhibits shouldn't interfere with the demo. Another radio in close proximity might (<1 foot). Now, if the RFI is at the carrier level (530Khz to 1640Khz), then other AM transmitters will wreak havok. Plan B, build some shielding around your exhibit? Back to case 1, (IF level), someone could deliberately tune their transmitter to your radio, then you'll just have to carry a big stick.

            Just my thoughts. Besides fixing some old radio's, I don't have first hand experience with Alair Radio Music.

            :)J
          • Dave McGuire
            ... It takes a lot less than that. Older micros with poor shielding and single-digit-MHz clocks still have signals with fast edge transitions, with strong
            Message 5 of 21 , Mar 28, 2013
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              On 03/28/2013 11:37 PM, Kyle Owen wrote:
              > > You all know about the famous "Fool on the Hill" demo. Bill Deg. demo'd it
              > > a couple of VCF Easts ago.
              > >
              > > InfoAge, at this year's Philadelphia Science Festival (April 20), is doing
              > > a "how radio works" theme. It was suggested that maybe MARCH could
              > > participate by doing the Altair demo several times during the day.
              > >
              > > I like that idea! But I wonder: with a bunch of radio gear operating in
              > > very close proximity, will the demo still work, or will there be too much
              > > interference for it to operate correctly?
              >
              > It's not at all likely that the radio stuff will interfere with the Altair.
              > It is likely, however, that the Altair will interfere with the radio stuff,
              > especially if the radio stuff is below 30MHz or so.
              >
              > Nah, only if you put a big 'ole Yagi on it! :)

              It takes a lot less than that. Older micros with poor shielding and
              single-digit-MHz clocks still have signals with fast edge transitions, with
              strong harmonic content well up into the tens of MHz.

              > Hey, at least it doesn't have
              > a switching supply built in. Those are the worst! The university's ham club
              > shack is almost unusable since the whole building is generating an untold
              > amount of RF noise from all of the computers.

              Yep. Yech. :-(

              -Dave

              --
              Dave McGuire, AK4HZ
              New Kensington, PA
            • Evan Koblentz
              ... I emailed Erik Klein (because he s done the demo) and he also suggested shielding around the exhibit. A quick Google search pointed me to simple directions
              Message 6 of 21 , Mar 28, 2013
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                >> Plan B, build some shielding around your exhibit?

                I emailed Erik Klein (because he's done the demo) and he also suggested shielding around the exhibit.

                A quick Google search pointed me to simple directions for making a Faraday cage, but doesn't that have to be 360 degrees? Obviously my shield needs at least one open side. Can a cage work with one open side? Or is there a simpler way to make a shield?
              • B Degnan
                ... Experiment...see what happens beforehand and act accordingly ... my guess it ll have no measurable effect past a few feet. For example I found that it did
                Message 7 of 21 , Mar 29, 2013
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                  Evan Koblentz <evan@...> wrote:

                  >>> Plan B, build some shielding around your exhibit?
                  >
                  >I emailed Erik Klein (because he's done the demo) and he also suggested
                  >shielding around the exhibit.
                  >
                  >A quick Google search pointed me to simple directions for making a
                  >Faraday cage, but doesn't that have to be 360 degrees? Obviously my
                  >shield needs at least one open side. Can a cage work with one open
                  >side? Or is there a simpler way to make a shield?
                  >
                  >
                  >
                  >
                  >------------------------------------
                  >
                  >Yahoo! Groups Links
                  >
                  >
                  >
                  Experiment...see what happens beforehand and act accordingly ... my guess it'll have no measurable effect past a few feet.

                  For example I found that it did not effect guitar amps thatwill were sometimes known to pick up police radio.

                  Set up the system get it working and position the am radio 2,5,10,20 feet.
                  --
                  Sent from my PDP 8/e.
                • joshbensadon
                  ... You are right to guess it needs to be 360 . These low frequency AM signals are like sound, they curve around objects to fill everything, vs high
                  Message 8 of 21 , Mar 29, 2013
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                    --- In midatlanticretro@yahoogroups.com, "Evan Koblentz" <evan@...> wrote:
                    >
                    > >> Plan B, build some shielding around your exhibit?
                    >
                    > I emailed Erik Klein (because he's done the demo) and he also suggested shielding around the exhibit.
                    >
                    > A quick Google search pointed me to simple directions for making a Faraday cage, but doesn't that have to be 360 degrees? Obviously my shield needs at least one open side. Can a cage work with one open side? Or is there a simpler way to make a shield?
                    >

                    You are right to guess it needs to be "360". These low frequency AM signals are like sound, they curve around objects to fill everything, vs high frequency which works only "line of sight".

                    I would try using aluminum (window) screen.

                    Another option might be to use a small radio that can be placed right inside the Altair. Start the demo by lifting the lid of the Altair to show off the cool boards inside, place your radio inside, close the lid. Finish the demo by pulling out the radio (for those new comers that didn't see the radio going in).

                    If you like to do your own experiments, you can buy an AM transmitter from Ramseykits for $35.
                    http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=AM1C

                    Or tune your AM radio to a local station and shielding it out.

                    :)J
                  • Systems Glitch
                    ... Ian and I found that the RF firehose coming from the Altair easily drowns out strong local AM stations. It also mostly overpowers FM stations as well, if
                    Message 9 of 21 , Mar 29, 2013
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                      > Or tune your AM radio to a local station and shielding it out.

                      Ian and I found that the RF firehose coming from the Altair easily drowns out strong local AM stations. It also mostly overpowers FM stations as well, if the radio is really close to the Altair. We also found that angle of the antenna to the Altair matters, so presumably the source(s) of RF from the Altair have some degree of polarization.

                      Thanks,
                      Jonathan
                    • jack99rubin
                      ... It wouldn t be a cage if you could get out! : ) Jack
                      Message 10 of 21 , Mar 29, 2013
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                        --- In midatlanticretro@yahoogroups.com, joshbensadon <no_reply@...> wrote:
                        >
                        > --- In midatlanticretro@yahoogroups.com, "Evan Koblentz" <evan@> wrote:
                        > >
                        > > >> Plan B, build some shielding around your exhibit?
                        > >
                        > > I emailed Erik Klein (because he's done the demo) and he also suggested shielding around the exhibit.
                        > >
                        > > A quick Google search pointed me to simple directions for making a Faraday cage, but doesn't that have to be 360 degrees? Obviously my shield needs at least one open side. Can a cage work with one open side? Or is there a simpler way to make a shield?
                        > >
                        >
                        > You are right to guess it needs to be "360". These low frequency AM signals are like sound, they curve around objects to fill everything, vs high frequency which works only "line of sight".
                        >

                        It wouldn't be a cage if you could get out! :>)
                        Jack
                      • Dave McGuire
                        ... Also, remember distance is your friend. unless there are directional antennas involved, signal strength is inversely proportional to the square of the
                        Message 11 of 21 , Mar 29, 2013
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                          On 03/29/2013 08:34 AM, joshbensadon wrote:
                          > You are right to guess it needs to be "360". These low frequency AM
                          > signals are like sound, they curve around objects to fill everything, vs
                          > high frequency which works only "line of sight".
                          >
                          > I would try using aluminum (window) screen.
                          >
                          > Another option might be to use a small radio that can be placed right
                          > inside the Altair. Start the demo by lifting the lid of the Altair to
                          > show off the cool boards inside, place your radio inside, close the lid.
                          > Finish the demo by pulling out the radio (for those new comers that didn't
                          > see the radio going in).
                          >
                          > If you like to do your own experiments, you can buy an AM transmitter from
                          > Ramseykits for $35.
                          > http://www.ramseyelectronics.com/cgi-bin/commerce.exe?preadd=action&key=AM1C
                          >
                          > Or tune your AM radio to a local station and shielding it out.

                          Also, remember distance is your friend. unless there are directional
                          antennas involved, signal strength is inversely proportional to the square of
                          the distance.

                          -Dave


                          --
                          Dave McGuire, AK4HZ
                          New Kensington, PA
                        • joshbensadon
                          ... Yes, I had that in mind too when I suggested putting the radio right inside the Altair box! Part of the demo is to show how it was done wirelessly, but
                          Message 12 of 21 , Mar 29, 2013
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                            --- In midatlanticretro@yahoogroups.com, Dave McGuire <Mcguire@...> wrote:

                            > > Another option might be to use a small radio that can be placed right
                            > > inside the Altair. Start the demo by lifting the lid of the



                            > Also, remember distance is your friend. unless there are directional
                            > antennas involved, signal strength is inversely proportional to the square of
                            > the distance.
                            >
                            > -Dave


                            Yes, I had that in mind too when I suggested putting the radio right inside the Altair box! Part of the demo is to show how it was done wirelessly, but given the circumstances, it might need to go inside the box. Also, he will need to watch that an open Altair box doesn't interfere with his neighbor's demo.

                            But, things might just work outside of the box, if the radio is placed at the right position/angle.

                            I wish I had more experience with the Altair Radio Music. But I know the AM Radio antenna is based on a ferret stick, which should be directional. But, I think the interference really happens at the IF stage, which is further down the receiver circuitry. If that is true, you could remove the ferret stick antenna.

                            I'm sure the demo will sound good enough to get the point across. I just like the idea of opening the Altair Lid to show off the internals.

                            :)J
                          • Dave McGuire
                            ... Ferrite ... Ferrite loopstick antennas are very broadly directional. They have nulls off the ends but they re not terribly deep. ... Actually I d be
                            Message 13 of 21 , Mar 29, 2013
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                              On 03/29/2013 11:46 AM, joshbensadon wrote:
                              >>> right inside the Altair. Start the demo by lifting the lid of
                              >>> the
                              >
                              >
                              >> Also, remember distance is your friend. unless there are
                              >> directional antennas involved, signal strength is inversely
                              >> proportional to the square of the distance.
                              >
                              > Yes, I had that in mind too when I suggested putting the radio right
                              > inside the Altair box! Part of the demo is to show how it was done
                              > wirelessly, but given the circumstances, it might need to go inside
                              > the box. Also, he will need to watch that an open Altair box doesn't
                              > interfere with his neighbor's demo.
                              >
                              > But, things might just work outside of the box, if the radio is
                              > placed at the right position/angle.
                              >
                              > I wish I had more experience with the Altair Radio Music. But I know
                              > the AM Radio antenna is based on a ferret stick,

                              Ferrite

                              > which should be directional.

                              Ferrite "loopstick" antennas are very broadly directional. They have
                              nulls off the ends but they're not terribly deep.

                              > But, I think the interference really happens at the IF
                              > stage, which is further down the receiver circuitry. If that is
                              > true, you could remove the ferret stick antenna.

                              Actually I'd be kinda surprised if the interference in question
                              happened at IF. Those IFs are typically 455KHz; you're much more likely
                              to get interference from higher frequencies than that in ~1~8MHz
                              microprocessor circuitry.

                              I've done it with a PDP-8; that interference comes from the
                              high-current pulses in the core memory subsystem if memory serves. The
                              interference there isn't at IF.

                              > I'm sure the demo will sound good enough to get the point across. I
                              > just like the idea of opening the Altair Lid to show off the
                              > internals.

                              I think it'll be great!

                              -Dave

                              --
                              Dave McGuire, AK4HZ
                              New Kensington, PA
                            • joshbensadon
                              ... Well, it could be a Ferret, but I guess the little critter would likely run away. ... You d think they should be omni directional, but this is getting OT.
                              Message 14 of 21 , Mar 29, 2013
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                                --- In midatlanticretro@yahoogroups.com, Dave McGuire <Mcguire@...> wrote:
                                > > the AM Radio antenna is based on a ferret stick,
                                >
                                > Ferrite
                                >

                                Well, it could be a Ferret, but I guess the little critter would likely run away.

                                > Ferrite "loopstick" antennas are very broadly directional.

                                You'd think they should be omni directional, but this is getting OT.

                                > Actually I'd be kinda surprised if the interference in question
                                > happened at IF. Those IFs are typically 455KHz; you're much more likely
                                > to get interference from higher frequencies than that in ~1~8MHz
                                > microprocessor circuitry.

                                Here, I will yield to your experience. I have never played with RFI Computer Music. Does the interference depend on where you tune your radio? If you are far away from your computer, does tuning your radio help bring in the signal? I'm sure there's lots to read about the subject, but playing is more fun.

                                :)J
                              • Mr Ian Primus
                                ... Hehehehe. I don t know, it might be patient. Ferrets like music, but I m not so sure they like RFI. Still, I can t imagine that wire wound around a ferret
                                Message 15 of 21 , Mar 29, 2013
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                                  --- On Fri, 3/29/13, joshbensadon <no_reply@yahoogroups.com> wrote:

                                  > > > the AM Radio antenna is based on a ferret stick,
                                  > >
                                  > >   Ferrite
                                  > >
                                  >
                                  > Well, it could be a Ferret, but I guess the little critter
                                  > would likely run away.

                                  Hehehehe. I don't know, it might be patient. Ferrets like music, but I'm not so sure they like RFI. Still, I can't imagine that wire wound around a ferret would make a very good antenna.


                                  > Here, I will yield to your experience.  I have never
                                  > played with RFI Computer Music.  Does the interference
                                  > depend on where you tune your radio?  If you are far
                                  > away from your computer, does tuning your radio help bring
                                  > in the signal?  I'm sure there's lots to read about the
                                  > subject, but playing is more fun.

                                  It seems to work the best, further down on the dial, but "tuning" isn't really the word for it. The computer kind of splatters the whole band, so, really, you're trying to tune OUT all the other "interference", (like those pesky radio stations) so you can find a clear spot where the computer is stronger.

                                  Honestly, it works pretty well, all things considered. As long as the radio is *close* to the computer, and the cover is off, it works incredibly well. You don't have to go stuffing the radio inside the machine, or doing anything fancy. Yes, you can figure out exactly at which frequencies on the radio the signal should be strongest, and mess with directionality of antennas, or ferrets, but you don't have to. Just put the radio next to the computer and fiddle with the knobs until you hear the music. The Altair is an RF sieve. When I tried it, I could even hear the computer music on the FM band in spots (it was faint, and in the background, but there).

                                  John even videotaped it when we got the program working on my machine:
                                  http://www.youtube.com/watch?v=tImrHlYLzZo

                                  So, yeah. RF music on S100 boxes works quite well. It really isn't that hard to do. At TCF, Corey entered the program into his system, and we put a random old AA5 radio I'd bought at the flea market area for a few bucks next to it, and it worked there too. We just set the radio next to the computer, with it's cover off, and had lovely RF noise/music playing loud and clear.

                                  -Ian
                                • B. Degnan
                                  ... really the word for it. The computer kind of splatters the whole band, so, really, you re trying to tune OUT all the other interference , (like those
                                  Message 16 of 21 , Mar 29, 2013
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                                    >
                                    > It seems to work the best, further down on the dial, but "tuning" isn't
                                    really the word for it. The computer kind of splatters the whole band, so,
                                    really, you're trying to tune OUT all the other "interference", (like those
                                    pesky radio stations) so you can find a clear spot where the computer is
                                    stronger.


                                    Wonder what a beat frequency oscillator would do for this kind of RF
                                    noise.
                                  • Dave McGuire
                                    ... Nicely done! ... Ahh, someone else who knows what an AA5 is! You rock. -Dave -- Dave McGuire, AK4HZ New Kensington, PA
                                    Message 17 of 21 , Mar 29, 2013
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                                      On 03/29/2013 03:27 PM, Mr Ian Primus wrote:
                                      > John even videotaped it when we got the program working on my machine:
                                      > http://www.youtube.com/watch?v=tImrHlYLzZo

                                      Nicely done!

                                      > So, yeah. RF music on S100 boxes works quite well. It really isn't that
                                      > hard to do. At TCF, Corey entered the program into his system, and we put
                                      > a random old AA5 radio I'd bought at the flea market area for a few bucks
                                      > next to it, and it worked there too. We just set the radio next to the
                                      > computer, with it's cover off, and had lovely RF noise/music playing loud
                                      > and clear.

                                      Ahh, someone else who knows what an AA5 is! You rock.

                                      -Dave

                                      --
                                      Dave McGuire, AK4HZ
                                      New Kensington, PA
                                    • joshbensadon
                                      ... There s an idea. I don t think the ferret would like it much though. I don t have ferrets, but I have cats, perhaps I can try it with one of them? Stay
                                      Message 18 of 21 , Mar 29, 2013
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                                        --- In midatlanticretro@yahoogroups.com, Mr Ian Primus <ian_primus@...> wrote:
                                        > > > > the AM Radio antenna is based on a ferret stick,
                                        > > >   Ferrite
                                        > > Well, it could be a Ferret, less the little critter run away
                                        >
                                        > Hehehehe. I don't know, it might be patient. Ferrets like music, but I'm not so sure they like RFI. Still, I can't imagine that wire wound around a ferret would make a very good antenna.

                                        There's an idea. I don't think the ferret would like it much though.
                                        I don't have ferrets, but I have cats, perhaps I can try it with one of them? Stay tuned! (My cats are looking at me, not amused).


                                        > John even videotaped it when we got the program working on my machine:
                                        > http://www.youtube.com/watch?v=tImrHlYLzZo

                                        Very cool! Thanks for the video.

                                        > So, yeah. RF music on S100 boxes works quite well. It really isn't that hard to do. At TCF, Corey entered the program into his system, and we put a random old AA5 radio I'd bought at the flea market area for a few bucks next to it, and it worked there too. We just set the radio next to the computer, with it's cover off, and had lovely RF noise/music playing loud and clear.


                                        Here's an idea. Get 2 Altairs to play dueling banjos (or Altairs).

                                        :)J
                                      • Evan Koblentz
                                        ... MARCH does have two of them...
                                        Message 19 of 21 , Mar 29, 2013
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                                          >> Here's an idea. Get 2 Altairs to play dueling banjos (or Altairs).

                                          MARCH does have two of them...
                                        • joshbensadon
                                          ... I want to see a video of them playing dueling banjo s!
                                          Message 20 of 21 , Mar 29, 2013
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                                            --- In midatlanticretro@yahoogroups.com, "Evan Koblentz" <evan@...> wrote:
                                            >
                                            > >> Here's an idea. Get 2 Altairs to play dueling banjos (or Altairs).
                                            >
                                            > MARCH does have two of them...
                                            >


                                            I want to see a video of them playing dueling banjo's!
                                          • Dave McGuire
                                            ... Not really; the EMI is very broadband. There are usually parts of the tuning range where it s stronger and/or more clear. And playing is DEFINITELY more
                                            Message 21 of 21 , Mar 29, 2013
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                                              On 03/29/2013 03:16 PM, joshbensadon wrote:
                                              > Here, I will yield to your experience. I have never played with RFI
                                              > Computer Music. Does the interference depend on where you tune your
                                              > radio? If you are far away from your computer, does tuning your radio
                                              > help bring in the signal? I'm sure there's lots to read about the
                                              > subject, but playing is more fun.

                                              Not really; the EMI is very broadband. There are usually parts of the
                                              tuning range where it's stronger and/or more clear.

                                              And playing is DEFINITELY more fun. :-)

                                              -Dave

                                              --
                                              Dave McGuire, AK4HZ
                                              New Kensington, PA
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