Posted: 12/21/2011 6:06:19 PM EDT
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Some background info since this is an RF problem, but NOT HAM-related, however I don't know where else I would post this since you guys are the RF experts.
I'm the head pyrotechnician for a touring show. Our system includes receivers operating on the 418mHz band. It's a code-hopping system to prevent unintentional misfires. Lately, I've been running into some issues that I can only assume are interference related. We run some separate wireless networking gear that also exhibits problems, typically connecting the client to the router, and these problems usually occur prior to issues with the pyro receivers, but always occur if the pyro has problems. I'm assuming they are related by way of interference, the network simply being touchier than the pyro, and the network problems are just indicative of a crowded environment across the UHF band. Correct me if I'm wrong but with the proliferation of wireless networking in the buildings we play this makes sense as the 2.4Ghz band is pretty crowded. I would like to give the performance director a solid answer, and if possible, prior warning in the event I can predict issues. I do not have 6 grand in my budget to pick up a spectrum analyzer, and it certainly wouldn't be worth the cost when I just need to look at 418 +/- a few mHz. Is there something I can build that will give an indication of interference in that small bandwidth range? Is something like the Oscium WiPry power deal a viable piece of hardware that would indicate interference? At this point I've ruled out anything hardware related and can only imagine that the signal isn't triggering the receivers. Every receiver is double redundant so unless multiple receivers are faulty for each effect, I have to conclude it's a signal issue. If I can get something that proves interference is the cause, is there anything I can do to make the signal more robust? Some of the arenas seem like they have pretty crowded air space. I CANNOT modify the receivers or the transmitter both from a legal, regulatory, as well as liability standpoint. I shouldn't have a problem buying any antennas or boosters however this has to travel, so anything larger than a 3-4' antenna will not work. If something packable is available it might be an option, something like the satcom antennas the SOCOM and FAC guys use but in the low end of th UHF band as opposed to satellite. Any thoughts would be greatly appreciated, the cheaper the better. Thanks. |
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You can get a handheld spectrum analyzer for less than $2K (but as a disclaimer, I do not have first-hand experience with any of them so I cannot vouch for performance or reliability).
For example, http://www.saelig.com/product/EMC002.htm You can see other models at http://www.saelig.com (do a search on 'spectrum') or elsewhere. |
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Transmitter & receiver
Formerly PyroPak, now owned by Ultratec, formerly Le Maitre. Transmitter is TM-16, receivers are RX-4 418mHz 4-channel receivers. Problem manifests itself as a no-fire. TM-16 has power, arm, and fire light when cue is triggered, pyro does not fire. Unfortunately all testing has to occur pre or post show so without an audience so any additional sources of interference may not be present. I can't imagine having a audience with their cameras and cell phones would be the cause but you never know. Typically a post-show test results in no problems so something during the show is causing the issue, although there are no other electronics around the pyro console. There is a powered "transmit amplifier" by "Professional Wireless, a Masque Sound company" in between the TM-16 and the antenna. The box says 450-698mHz, outside of the range that our equipment operates on but apparently whoever ordered it had assurances by the company that it covered the entire 400mHz band. Whether this is true I don't know, however I don't believe it attenuates frequencies outside of its bandwidth so even if it's not working, it shouldn't cause issues according to the non-expert who ordered it. Unfortunately he's very little help. Thanks for the lead on the spectrum analyzer. Any chance that anyone makes one cheaper? Possibly less feature-filled as I'm spending someone else's money. Although I may just pick it up for personal use anyway. |
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Dang, I've been trying not to post anything...
Is this a new problem or has this been a lingering issue? Have you changed the batteries in the receivers? Can they be weak? Does your transmitter draw the increased current it should when it switches to a transmit state? I was going to ask if you can recreate or test it in a similar environment until I realize you can't run out like a bunch of monkeys during a show. Maybe you can test this somehow in a similar crowded environment using a similar electrical load that isn't a pyro. Have you contacted the correct person at the manufacturer? I would consider using a portable antenna for your transmitter to help gain the advantage, but I must be careful not to chase the wrong squirrel up the wrong tree in the wrong park. I have wondered what kind of interference and noise issues arise when there is a crapload of cell phones in an auditorium or arena. Good luck. |
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418 MHz- sounds like part 15 devices, I wouldn't expect much. You will be limited on what you can LEGALLY use for transmit antennas, but I reckon you could put whatever you want on the receivers. IF these are unlicensed devices as I suspect they are, all the money in the world for spectrum analyzers will not empower you to change a darn thing without cooperation, but in arenas it may be security systems killing you and they might be able/willing to power off during an event.
Around here the nodding donkeys have some sort of RF telemetry/control, most have little 5 el. yagis & looking at the size they have to be somewhere close to that freq. These antennas measure roughly 12" X 18" occupying a horizontal plane. Such wouldn't cost a whole lot each but if you have a receiver per function it will add up quick, plus supports, feedlines, and so on. |
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Quoted:
Some background info since this is an RF problem, but NOT HAM-related, however I don't know where else I would post this since you guys are the RF experts. I'm the head pyrotechnician for a touring show. Our system includes receivers operating on the 418mHz band. It's a code-hopping system to prevent unintentional misfires. Lately, I've been running into some issues that I can only assume are interference related. We run some separate wireless networking gear that also exhibits problems, typically connecting the client to the router, and these problems usually occur prior to issues with the pyro receivers, but always occur if the pyro has problems. I'm assuming they are related by way of interference, the network simply being touchier than the pyro, and the network problems are just indicative of a crowded environment across the UHF band. Correct me if I'm wrong but with the proliferation of wireless networking in the buildings we play this makes sense as the 2.4Ghz band is pretty crowded. I would like to give the performance director a solid answer, and if possible, prior warning in the event I can predict issues. I do not have 6 grand in my budget to pick up a spectrum analyzer, and it certainly wouldn't be worth the cost when I just need to look at 418 +/- a few mHz. Is there something I can build that will give an indication of interference in that small bandwidth range? Is something like the Oscium WiPry power deal a viable piece of hardware that would indicate interference? At this point I've ruled out anything hardware related and can only imagine that the signal isn't triggering the receivers. Every receiver is double redundant so unless multiple receivers are faulty for each effect, I have to conclude it's a signal issue. If I can get something that proves interference is the cause, is there anything I can do to make the signal more robust? Some of the arenas seem like they have pretty crowded air space. I CANNOT modify the receivers or the transmitter both from a legal, regulatory, as well as liability standpoint. I shouldn't have a problem buying any antennas or boosters however this has to travel, so anything larger than a 3-4' antenna will not work. If something packable is available it might be an option, something like the satcom antennas the SOCOM and FAC guys use but in the low end of th UHF band as opposed to satellite. Any thoughts would be greatly appreciated, the cheaper the better. Thanks. Have you considered noise on the AC that powers everything? Maybe something you're plugging in with everything else is putting noise on the line. Hard to imagine something on the RF side messing with both systems, with the frequencies so far apart. Unless of course, 418 mHz if an IF of the 2.4 gig. |
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Issue is intermittent. Show fired fine tonight, although first show today did not.
Power for the transmitter is sourced from a 400A service to our Skjonberg-built distros into a 220v APC battery/conditioner down to 110 line voltage at the console/transmitter. It's as clean as we can get it. Power for the receivers are batteries changed before every show and charged in between. The receivers have on-board fault testing that determine if there's enough juice to fire, and they are checked just prior to the effect. We have both an omni, as well as yagi's sourced directly from the manufacturer. There doesn't seem to be a difference in performance either way, we do not use the antenna native to the TM-16 as it's never worked. We're currently using the omni. You can see both on the website. There may be issues involved with placement of the yagi when my previous co-worker tried it. I don't have any documentation regarding proper installation which is another issue. The receivers are about 150ft apart at opposite ends of the arena so I don't know if the yagi will hit both although I am game to try. As far as the amplifier, the manufacturer won't provide technical details so talking to them just illicit's a "well it's probably interference." The amplifier manufacturer and the transmitter manufacturer being different companies doesn't help as the both tell you to call the other. As far as unregulated, I don't know either way, I'll have to research more. Being a pyrotechnic transmitter I would imagine that there is some regulation involved. The potential for disaster is pretty great if someone could click their garage door opener and set of a mortar chase, but assuming they do things intelligently in this industry is probably the fastest way to an early death and a write-up in OSHA's latest "check out what this dumb shit did" article. Also turning off any building systems/security will be a no go. We have a hard enough time getting smoke detectors turned off and fire marshal's are particularly touchy since we have 4 alcohol flame projectors. I'll try and get more technical information. Thanks for the help thus far. If nothing else I'm coming up with a good list of questions for the manufacturer I can shoot up the line. Next call is to the owner. |
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Quoted:
If you are within a few hundred feet of the rcvr and xmtr and running amplifiers  -maybe you are overdriving the receivers?
Had not considered this. Would intermittent operation exist under these circumstances? I'm more than willing to throw stuff away if it's not helping at all, and that amplifier is just one more thing that can break to begin with. I'm thinking about getting this to see if I get a spike @ each receiver location whenever the transmitter throws signal. This make sense or would this be a waste of money? Provided nothing breaks it'll still take a couple months to get the budget for a real spectrum analyzer approved, I was thinking this would at least give me a little insight in the mean time. It would also give me a convenient reason to write off my iPad, so double bonus. It should allow me to get an accurate reading during the show since I can stash my phone by the receiver during actual show conditions. If this is a terrible idea let me know before I waste the cash. I've got e-mails going out to get as much technical info on the equipment as possible. The guy I replaced has nothing, and the show I came from had different gear so it's becoming sort of a steep learning curve trying to sort out their mess. |
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There is not nearly enough information here for to provide any more than the most general guidance to you. Nor do you really have the budget to buy or rent the equipment necessary to really debug this in a definitive way. There is also the matter of training and knowledge to use such test equipment (no offense meant).
You have said the equipment is 100% reliable before and after the show, just not during. Other than a venue full of cell phones, which very well could be the difference, what other changes in the environment are in place during the show? Are there any other radio mic's or wireless links that are used on stage that are not active during set-up/breakdown? What about the temperature in the area of the receivers (or even transmitter)? Are the receivers in a rack with a bunch of dimmer packs that are getting hot during the show? Electronic noise (EMI) from dimmer packs that are actively making scene changes during the show vs. them being quiescent during set-up/breakdown testing could also be an issue. Were these considered reliable before you took over pyro duties? Did you change something in the setup when you took over, for instance do you run your cables in a different way on stage, did you move where the receivers are compared to your predecessor? The comment on the amp being unnecessary is interesting. The fact that there is an amplifier there is somewhat suspicious. Did your predecessor have a problem and he "fixed" it with the amp? And, simplest of all, there is no way to be certain that all of your equipment is in good repair. RF is invisible. That little power meter you have found is a joke. You have limitations where test equipment is concerned. However you can check things out by substituting hardware. You say that multiple receivers have exhibited the problem. This points the finger at a faulty transmitter or faulty RF amplifier or faulty antenna/antenna cable. Can you borrow or lease new transmitter/amp/antenna hardware and see if that fixes the problem? |
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Quoted:
There is not nearly enough information here for to provide any more than the most general guidance to you. Nor do you really have the budget to buy or rent the equipment necessary to really debug this in a definitive way. There is also the matter of training and knowledge to use such test equipment (no offense meant). This is pretty much what I figured. I was hoping there was a simple testing solution, like a tick tracer equivalent for rf. My lack of knowledge of the testing equipment certainly drives this. Not everyone can use a DMM or an oscilloscope, but give someone a tick tracer and they have to be pretty stupid if they can't figure out how to use it. I can understand if there isn't an equivalent, just wishful thinking on my part. You have said the equipment is 100% reliable before and after the show, just not during. Other than a venue full of cell phones, which very well could be the difference, what other changes in the environment are in place during the show? Are there any other radio mic's or wireless links that are used on stage that are not active during set-up/breakdown? What about the temperature in the area of the receivers (or even transmitter)? Are the receivers in a rack with a bunch of dimmer packs that are getting hot during the show? Electronic noise (EMI) from dimmer packs that are actively making scene changes during the show vs. them being quiescent during set-up/breakdown testing could also be an issue.
There really aren't many environmental changes during the show. There are no dimmer racks and the receivers are suspended away from the lighting rig. No other wireless is operating during the show. Heat wise, they're both fairly separated from any real source of heat. Although suspended from the lighting rig, the closest lighting fixture is probably 10 feet away. Typically the grid is only marginally hotter than the rest of the environment, but the receivers are lower than the rest of the grid so convection would be working away from the receivers. No dimmer racks of which to speak, 140 Mac 2k's, all of which have been doing their thing during testing, specifically to rule this out. I could see issue with one set of receivers as they are suspended and moving underneath a fly car. It's basically a 3-phase motor that drives on a track, with a winch that raises and lowers. My reasoning behind dismissing this is that often these receivers will still fire, even if the downstage receiver doesn't. It may be proximity overriding any interference generated by the motor as those receivers are substantially closer to the transmitter? Were these considered reliable before you took over pyro duties? Did you change something in the setup when you took over, for instance do you run your cables in a different way on stage, did you move where the receivers are compared to your predecessor?
Issues are not new, apathy simply prevailed in the past. I'm not big on giving bullshit answers to the production office so I'm trying to track it down. Even if there's nothing I can do, I'd at least like a definitive answer. Nothing in the setup has changed, consistency is key on the road. Unfortunately, although the setup is consistent, the performance of the system is not. It will go weeks without issue, then it may be day to day for a week. The comment on the amp being unnecessary is interesting. The fact that there is an amplifier there is somewhat suspicious. Did your predecessor have a problem and he "fixed" it with the amp?
You're touching on something I'm seriously considering. Unfortunately, like you said, without the proper test equipment and knowledge it's something that I might not be able to track down. There isn't anybody in the company with the knowledge or training to figure it out, I think the amp was just a canned answer. Considering it's outside of the transmitter/receiver band, I think it may just be luck that it's worked since it was put in line. And, simplest of all, there is no way to be certain that all of your equipment is in good repair. RF is invisible. That little power meter you have found is a joke. You have limitations where test equipment is concerned. However you can check things out by substituting hardware. You say that multiple receivers have exhibited the problem. This points the finger at a faulty transmitter or faulty RF amplifier or faulty antenna/antenna cable. Can you borrow or lease new transmitter/amp/antenna hardware and see if that fixes the problem?
The thing that leads me to believe it's not the equipment is that it's so widespread. Problems have occurred across 8 receivers, 4 transmitters, with two styles of antenna's. I highly doubt I'll get permission to swap out gear at this point. The latest discussions seem to lean towards this being something we deal with. It's been ok for the last couple of shows so until it gets to the point where we are having more malfunctions than successful fires it looks like it's just something that's gonna get glossed over. I'm not really excited about it, I'd just like to get a definitive cause. The intermittent behavior is a road block in getting replacement gear as well, and as much as I'd like to take a sledge to the gear and force the issue, that wouldn't work out so well for me. I'll forego that crappy little iDevice, I didn't really had high hopes that it would help, again budget constraints weigh-in. |
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Quoted:
There is not nearly enough information here for to provide any more than the most general guidance to you. Nor do you really have the budget to buy or rent the equipment necessary to really debug this in a definitive way. There is also the matter of training and knowledge to use such test equipment (no offense meant). This is pretty much what I figured. I was hoping there was a simple testing solution, like a tick tracer equivalent for rf. My lack of knowledge of the testing equipment certainly drives this. Not everyone can use a DMM or an oscilloscope, but give someone a tick tracer and they have to be pretty stupid if they can't figure out how to use it. I can understand if there isn't an equivalent, just wishful thinking on my part. You have said the equipment is 100% reliable before and after the show, just not during. Other than a venue full of cell phones, which very well could be the difference, what other changes in the environment are in place during the show? Are there any other radio mic's or wireless links that are used on stage that are not active during set-up/breakdown? What about the temperature in the area of the receivers (or even transmitter)? Are the receivers in a rack with a bunch of dimmer packs that are getting hot during the show? Electronic noise (EMI) from dimmer packs that are actively making scene changes during the show vs. them being quiescent during set-up/breakdown testing could also be an issue.
There really aren't many environmental changes during the show. There are no dimmer racks and the receivers are suspended away from the lighting rig. No other wireless is operating during the show. Heat wise, they're both fairly separated from any real source of heat. Although suspended from the lighting rig, the closest lighting fixture is probably 10 feet away. Typically the grid is only marginally hotter than the rest of the environment, but the receivers are lower than the rest of the grid so convection would be working away from the receivers. No dimmer racks of which to speak, 140 Mac 2k's, all of which have been doing their thing during testing, specifically to rule this out. I could see issue with one set of receivers as they are suspended and moving underneath a fly car. It's basically a 3-phase motor that drives on a track, with a winch that raises and lowers. My reasoning behind dismissing this is that often these receivers will still fire, even if the downstage receiver doesn't. It may be proximity overriding any interference generated by the motor as those receivers are substantially closer to the transmitter? Were these considered reliable before you took over pyro duties? Did you change something in the setup when you took over, for instance do you run your cables in a different way on stage, did you move where the receivers are compared to your predecessor?
Issues are not new, apathy simply prevailed in the past. I'm not big on giving bullshit answers to the production office so I'm trying to track it down. Even if there's nothing I can do, I'd at least like a definitive answer. Nothing in the setup has changed, consistency is key on the road. Unfortunately, although the setup is consistent, the performance of the system is not. It will go weeks without issue, then it may be day to day for a week. The comment on the amp being unnecessary is interesting. The fact that there is an amplifier there is somewhat suspicious. Did your predecessor have a problem and he "fixed" it with the amp?
You're touching on something I'm seriously considering. Unfortunately, like you said, without the proper test equipment and knowledge it's something that I might not be able to track down. There isn't anybody in the company with the knowledge or training to figure it out, I think the amp was just a canned answer. Considering it's outside of the transmitter/receiver band, I think it may just be luck that it's worked since it was put in line. And, simplest of all, there is no way to be certain that all of your equipment is in good repair. RF is invisible. That little power meter you have found is a joke. You have limitations where test equipment is concerned. However you can check things out by substituting hardware. You say that multiple receivers have exhibited the problem. This points the finger at a faulty transmitter or faulty RF amplifier or faulty antenna/antenna cable. Can you borrow or lease new transmitter/amp/antenna hardware and see if that fixes the problem?
The thing that leads me to believe it's not the equipment is that it's so widespread. Problems have occurred across 8 receivers, 4 transmitters, with two styles of antenna's. I highly doubt I'll get permission to swap out gear at this point. The latest discussions seem to lean towards this being something we deal with. It's been ok for the last couple of shows so until it gets to the point where we are having more malfunctions than successful fires it looks like it's just something that's gonna get glossed over. I'm not really excited about it, I'd just like to get a definitive cause. The intermittent behavior is a road block in getting replacement gear as well, and as much as I'd like to take a sledge to the gear and force the issue, that wouldn't work out so well for me. I'll forego that crappy little iDevice, I didn't really had high hopes that it would help, again budget constraints weigh-in. I hope new equipment is not more important that a Great White scenerio. BTW good luck. I have had RF issues drive me crazy. Usually my issue is a ground. |
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Long time touring lighting guy here...
If you are in Nashville in the next few weeks I can come down and see if I can help you track down some of the issues. 2 relatively inexpensive tools, which in combination may help you deal with Rf issues. first... freq counter like this one: http://www.gigaparts.com/store.php?action=profile&sku=ZMF-888 need to know with some specificity where these xmitters are outputting... Then get a UHf scanner, or ham HT... and listen in on that same frequency. transmit the fire commands with the recievers off, so you can tell what the signal should sound like.... (you may also be able to hear over mod if that is an issue.).... and then listen. Some other questions... Does the show move around alot? are there some cities that seem to have more problems than others? Theatrical show or music? opening acts? With 2 shows a day and arenas my gut says TSO ?.... (If so, I know quite a few folks out there) Any venues firing up wireless clear-com or assisted listening devices? (some places don't turn them on until doors) What does your audio RF stuff look like? Lots of wireless mics and in-ears? or no?.... Most national level sound companies have spectrum analyzers, and may be able to get one for you for a few weeks. Are strobes firing when the pyro should be going off? how about truss/motor moves? These can put out some very short bursts of wideband noise. The problem troubleshooting this is you often need to have all the production elements running in show conditions, because there can often be isolated noise sources that need everything combined to create the conditions that generate it. Hope this helps.... Next week I'll drop a line to a few other touring pyro guys and see if any of them know anything about the old Pyro-Pak/LeMatire stuff RB Lighting crew chief Lots of big arena and stadium tours |
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Just off the top of my head, I'd take a look at what the differences are between functional and non-functional periods, with an eye to guitar amps, RF microphones and instrument RF transmitters. When you do your set-up, and your gear functions....are the band's amplifiers and transmitters operating? They are undoubtedly running during the show...but are they still on when your post show function testing is done? I would take a look at whatever electroic devices are in closest proximity to your gear first, then as potential sources of interferance are eliminated, expand the search area. Good luck with it. Keep us posted.  |
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Quoted:
Quoted:
If you are within a few hundred feet of the rcvr and xmtr and running amplifiers -maybe you are overdriving the receivers?
Had not considered this. Would intermittent operation exist under these circumstances? I'm more than willing to throw stuff away if it's not helping at all, and that amplifier is just one more thing that can break to begin with. I'm thinking about getting this to see if I get a spike @ each receiver location whenever the transmitter throws signal. This make sense or would this be a waste of money? Provided nothing breaks it'll still take a couple months to get the budget for a real spectrum analyzer approved, I was thinking this would at least give me a little insight in the mean time. It would also give me a convenient reason to write off my iPad, so double bonus. It should allow me to get an accurate reading during the show since I can stash my phone by the receiver during actual show conditions. If this is a terrible idea let me know before I waste the cash. I've got e-mails going out to get as much technical info on the equipment as possible. The guy I replaced has nothing, and the show I came from had different gear so it's becoming sort of a steep learning curve trying to sort out their mess. IMO it would be a waste of money for that application. If you want to investigate power level, a more meaningful diagnosis would be to place attenuators in line with the antenna and see how many 10's of dB's you can insert before errors occur. Do that at both the transmitter and receivers. Nice HP step attens are available on ebay. I can recommend, or not, your choice. I do this on wireless links at 2.4 and 5.8 ghz and have seen too strong signals create lower thruput. |
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Another issue is the real likelyhood of interference from other equipment as others have mentioned. The equipment could be a distant TV transmitter.
Fairly narrow and lowloss bandpass filters are available or can be quickly made to put on the antenna input of each receiver and would greatly reduce the probability of stray signals interfering with them. Can you open up one of the receivers and post a pix so we can possibly see what the RF input stages are using for preselection? |
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One final thought is to survey the transmitters you are using near by the receiver and see if they transmit on a similar frequency.
Even if they don't it's easily possible a higher freq and stronger signal could be getting into the receiver and causing it to miss data. Less likely a lower freq sig is but still possible. IMO, this shouldn't be difficult to diagnose. |
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Great White was another issue entirely. And the product is pretty safe as far as pyro is concerned. It's all pre-packed so you can't tweak the compound. It's burning, but it's fairly "cold" as far as pyro is concerned. You can put your hand a foot above the gerbs and you won't get burned.
RB, thanks for the links. I'll check it out. To answer your questions, touring show, large arenas, no music, all playback from a ProTools/Meyer powered rig. It'd be nice if it was TSO, I'd be making a lot more money  It's Disney on Ice.
No wireless at all from what I've seen at the building, all of our Clear Com is wired and spot-com and fly-com are on separate systems. No IEM's, only mic is a pre-show PR and that's maybe twice a week. No strobes, no motors moving except the fly car. It's the automaton I mentioned in a previous post. It's actually a pretty sterile environment as far as it's all concerned. It's frustrating, I'm a console guy. I can tear down and put back together damn near any console on the road, then program it blindfolded, and I can troubleshoot dmx and Artnet like a boss. This RF stuff is just being stupid. Interestingly enough last week we were at Staples in LA, no problems, this week in Anaheim I'm having issues. We've tested all of it during actual show conditions, timecode running, lights being blinky, carps sitting on their ass as usual. Neither makes a difference. It's just so damn intermittent that it's driving me crazy. |
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Quoted:
The thing that leads me to believe it's not the equipment is that it's so widespread. Problems have occurred across 8 receivers, 4 transmitters, with two styles of antenna's.[/span] With those sort of widespread and consistent problems my thought process is now going down the line of the products you have there are simply junk. Although it sounds like this will be a non-starter budget-wise it seems like it is time to switch to another equipment manufacturer. |
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Another thought... if they are fixed frequency... look up their fcc I.D. here:
FCC ID search The ID should be printed on every device. If it only lists one or 2 frequencies, you can probably forgo the frequency counter i mentioned earlier, and just get a scanner that will listen to the listed frequency. RB |
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There are any number of potential issues, even beyond the idea of RF interference on your control frequency, but for discussion let's try to resolve an RF interference issue.
418 is likely to be a somewhat problematic part of the spectrum. First, the 406-420 range is used by federal government users, so you may have some interference right on top of you. If that's the case, you need to change frequencies as there is nothing you can do. Second, it's close enough to LMR users in the 450-470 range, and also the common GMRS and FRS radios in the 460s that you may be getting some intermod and front end overload problems. Depending on where you are, TV stations start at 470 and go up from there which would only add to the intermod. With the proliferation of digital wireless phones, any time you have a crowd you're going to have a massive broadband RF noise generation in the phone bands which provides a fertile environment for intermod all over the spectrum. Depending on the budget, availability of other options, etc, what I would probably do if I was trying to solve an RF issue is to put the receiver in an enclosure to shield it from direct RF, then put a tuned cavity filter in the receive path to attenuate off-frequency signals to try to reduce or eliminate the intermod, front end overload, or direct RF into the circuitry of the receiving device. Don't discount the possibility that you maybe getting interference into the system by means other than the antenna, such as via power connection or the wires running to your firing circuits. |
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Last half of the week was ok. Dunno if anything changed but everything fired. Ontario this week, load in tomorrow, we'll see how it goes, but I'll let everyone know the outcome.
I agree the gear is probably crappy, was just saying that I doubt it's a malfunctioning piece of gear as it happens with all of it, I can't single one piece out for failure. I also agree hardwiring is the best bet. Unfortunately that isn't possible. Wireless is what I've gotta work with. RB, I'll get the FCC ID's tomorrow and plug them in and see if they come up with anything. Thanks guys, will report back as soon as I can. |
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Johnny, the recvr is in the upper right in the lower pix.
Some garage door openers have better receivers that that.  I hope those don't cost much.
As mentioned earlier, the amt of preselection on those kinds of receivers is minimal and a simple ceramic or SAW filter on the antenna input would likely resolve your issue. Unless the licence free band at 413 mc is being heavily used by other equipment, you can listen to the digital modulation with a scanner set to AM mode and tell. |
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Quoted:
As mentioned earlier, the amt of preselection on those kinds of receivers is minimal and a simple ceramic or SAW filter on the antenna input would likely resolve your issue. I didn't think about it earlier but a simple 1/4 wave stub on the input would provide a bit of input filtering at low cost. Should probably come up with some at least basic filtering on the control inputs or outputs that you have at the bottom. |
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SAW filters? Quarter wave stubs? Come on, guys, you've got to give Johnny something he has a realistic expectation of accomplishing.
GREAT PHOTOS! This is what we needed! The data sheets for the radios are here: http://www.radiometrix.com/content/tx2 You appear to have a somewhat older version based on the visible part number so this data sheet may not be entirely accurate. These radios are a joke. Typical Part 15 type crap. Garage door opener type stuff. They don't even claim FCC type authorization. The transmitter is 9dBm nominal, that's less than 8mW, and the spec sheet says it could be as low as 6dBm, which is 4mW. And the spec sheet only covers 432MHz. We can only assume it's the same at 418. Now we have all the data we need on the transmitter and receiver modules. Let's move on... We need the part number and data sheet on your PWS amp. I looked on the PWS web site. http://www.professionalwireless.com/, and they don't even show an amp. We need this data because we need to determine if 4 or 8mW is enough drive for that amp and the true bandwidth of the amp. If either or both are incorrect then the amp could actually be hurting you. PHOTOS HERE AS WELL, PLEASE. We need the part number and data sheet on your antennas. If they are the standard rubber duckies that came with the Pyropak stuff you won't be able to get that data, but tell us if that is the case. If the antennas are 450MHz antennas they could be hurting more than helping. PHOTOS PLEASE. Amps and antennas are your only salvation if you can't replace the Pyropak stuff. But they need to be the right amps and antennas. Also, remind us how far the maximum distance is between transmitter and receiver. Thanks, aa |
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Just a couple of notes. I played with a similar system 15 years ago, except it used Motorolla radios (a Saber IIRC). It used a public freq as well, the idea was it took a 6-10 digit code (DTMF in this case) to set off the explosives and IIRC, there was an Arming code thatr had to be entered before. This pretty much rules out false detonations. I would have boiught one except for the risk of smasking the box with fly rock.
I'd look at the amp. Anyone with a service monitor can measure the Signal to Noise ratio (called SINAD in this industry) of the amp. A two way shop should be willing to do it for $50, I bet an employee would do it on the side for $20.. I'd have them measure the output power of the transmitter, and use that from their input level for checking SINAD. Takes 5 minutes or less. The fact that Yagis don't make a difference really points to interference not being an issue. Just remember Yagis have lots of sidelobes where they are really strong,so they won't allways null out the interference, but you still get the advantage of a much hotter signal form the transmitter. One thing to try is to flip polerazation- If the yagi wire point up and down rotate them left and right. Both ends have to be the same. Also check your power supply voltage. Stuff acts really funny when voltage drops. There was a situation about 5 years ago, where dozens of radiostations were"taken over" by EAS because of a bad power supply in the ENDEC at one station that kept making it reeboot and send the monthly test message. |
Pictures of the amp and antenna that's on the receivers. The antennas we've used with the transmitter are: same antenna as the receivers, yagi on the pyropak website, and omni-directional on the pyropak website. The omni is made by Laird, that's the only information anywhere on the antenna. Amp has no other information than what's on the pictures, and it's already been brought up that the frequency bandwidth does not include the frequency on which our transmitters and receivers operate.
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Pictures of the amp and antenna that's on the receivers. The antennas we've used with the transmitter are: same antenna as the receivers, yagi on the pyropak website, and omni-directional on the pyropak website. The omni is made by Laird, that's the only information anywhere on the antenna. Amp has no other information than what's on the pictures, and it's already been brought up that the frequency bandwidth does not include the frequency on which our transmitters and receivers operate. http://img97.imageshack.us/img97/8707/photo2cwo.jpg http://img651.imageshack.us/img651/5514/photo3sg.jpg http://img684.imageshack.us/img684/2264/photo4dr.jpg I know you mentioned it, but "There's yer problim:" the amp is tuned for 450 MHz on the low side and you're feeding 415 MHz into it. If it's a decent amplifier (which I wouldn't count on) then the signal will actually be filtered out since it should bandpass everything going into it. You might actually be attenuating your signal by using that amplifier rather than amplifying it. And if it is amplifying it, it's because the tuned circuit sucks (or there isn't one) and it's passing on a nasty mess to the antenna. That amplifier can probably be returned for the frequencies you're using by a radio shop. |
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At the distances you're operating, why in the world do you need an amplifier??? No freaking clue. Again, I inherited this charlie foxtrot. I ran a similar setup on another show, but 1-channel receivers and the standard shortie antenna on the TM-16 and never had any problems throughout Europe and the States. However, this show is playing a lot of buildings I've never played before so I haven't made any changes to the setup as yet. I was wondering why an amplifier was needed when the receivers at 110ft and 30ft away respectively at the time of firing (took a disto to the receivers today). I think tomorrow I'll pull the amp out of the loop, put the standard antenna on and see if there are any issues, I'll put the omni back in line if the shorty doesn't reach. |
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At the distances you're operating, why in the world do you need an amplifier??? No freaking clue. Again, I inherited this charlie foxtrot. I ran a similar setup on another show, but 1-channel receivers and the standard shortie antenna on the TM-16 and never had any problems throughout Europe and the States. However, this show is playing a lot of buildings I've never played before so I haven't made any changes to the setup as yet. I was wondering why an amplifier was needed when the receivers at 110ft and 30ft away respectively at the time of firing (took a disto to the receivers today). I think tomorrow I'll pull the amp out of the loop, put the standard antenna on and see if there are any issues, I'll put the omni back in line if the shorty doesn't reach. Good plan. How about they Yagi antenna? At 418MHz it will have a beamwidth of a good 45 degrees. |
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Another update. Removed the amplifier from the system, re-programmed the cue stack with a .1 second delay before sendInc multiple fire commands instead of what appeared to be a burst of multiple commands, and thus far haven't had any problems here in Long Beach. Still using the omni, next week I might try and use the yagi to see if it makes any difference. I don't necessarily want to fix what's not broken but I'd still like to give a definitive answer since the last guy had problems with and without the amp and with each different antenna. If anyone happens to be in Vegas next week and would like to see the piece of crap I'm working with give me a shout and I'll score you some tickets so you can laugh in my general direction.
On another note, I talked to some of our show support about the quality of the components we use and presented them with the data from the radio chip manufacturer and they seemed a little shocked. They are discussing replacing the equipment on a further shows. We'll see if it works out, I kinda doubt it, but the problem has been run up the chain at least. Thanks for everyone's help, I really appreciate it. RB, if you know anyone that needs a rigger or a console programmer let me know, I'm getting burned out on this ice show crap!!! |
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Another update. Removed the amplifier from the system, re-programmed the cue stack with a .1 second delay before sendInc multiple fire commands instead of what appeared to be a burst of multiple commands, and thus far haven't had any problems here in Long Beach. Ah! Very good point! Bet this fixes it permanently! Sometimes you can't see the forest for the trees. |
| First thought in my mind is amp........due to everything that everybody has already talked about. You can rent a spectrum analyzer for a month for less than a grand, but you may no have the necessary experience to make sense of its output. How about renting or demo'ing a different setup, for just a few shows? TT |
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I am not qualified to help here, but in studying fit the extra license, I came across this.
E4E11 What is the most likely cause if you are hearing combinations of local AM broadcast signals inside one or more of the MF or HF ham bands? Nearby corroded metal joints are mixing and re-radiating the BC signals. Posted Via AR15.Com Mobile |
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Another update. Removed the amplifier from the system, re-programmed the cue stack with a .1 second delay before sendInc multiple fire commands instead of what appeared to be a burst of multiple commands, and thus far haven't had any problems here in Long Beach. Ah! Very good point! Bet this fixes it permanently! Sometimes you can't see the forest for the trees. Johnny––thinking about this some more, which is difficult because I don't have the data sheet on the programmable controller and I'm making a number of HUGE assumptions, but I bet that the controller, which probably can fire truly simultaneous channels, doesn't realize that the TM16 cannot, i.e. I'm making an assumption that the TM16 can only fire one RF channel at a time. You need to give it time to transmit the firing data command for each channel. So it you've got pyro on 4 channels of your TM4 and you need it to all go truly simultaneously you need to move it all onto a single TM4 channel. |
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Another update. Removed the amplifier from the system, re-programmed the cue stack with a .1 second delay before sendInc multiple fire commands instead of what appeared to be a burst of multiple commands, and thus far haven't had any problems here in Long Beach. Ah! Very good point! Bet this fixes it permanently! Sometimes you can't see the forest for the trees. Johnny––thinking about this some more, which is difficult because I don't have the data sheet on the programmable controller and I'm making a number of HUGE assumptions, but I bet that the controller, which probably can fire truly simultaneous channels, doesn't realize that the TM16 cannot, i.e. I'm making an assumption that the TM16 can only fire one RF channel at a time. You need to give it time to transmit the firing data command for each channel. So it you've got pyro on 4 channels of your TM4 and you need it to all go truly simultaneously you need to move it all onto a single TM4 channel. Not the case. Not how the show fires. Only 1 channel on the RX-4's is utilized at any given time, no more than one effect fires consecutively within an individual cue, it simply transmits the fire signal 4 times with a .1 second delay in between so that it gets 4 fire signals within a duration of about half a second per cue. There is sufficient time between cues that each cue has fully fired before moving on to the next one. Excellent idea though, I can see how it would work well if we were firing multiple effects within an individual cue. |
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Another update. Removed the amplifier from the system, re-programmed the cue stack with a .1 second delay before sendInc multiple fire commands instead of what appeared to be a burst of multiple commands, and thus far haven't had any problems here in Long Beach. Ah! Very good point! Bet this fixes it permanently! Sometimes you can't see the forest for the trees. Johnny––thinking about this some more, which is difficult because I don't have the data sheet on the programmable controller and I'm making a number of HUGE assumptions, but I bet that the controller, which probably can fire truly simultaneous channels, doesn't realize that the TM16 cannot, i.e. I'm making an assumption that the TM16 can only fire one RF channel at a time. You need to give it time to transmit the firing data command for each channel. So it you've got pyro on 4 channels of your TM4 and you need it to all go truly simultaneously you need to move it all onto a single TM4 channel. Not the case. Not how the show fires. Only 1 channel on the RX-4's is utilized at any given time, no more than one effect fires consecutively within an individual cue, it simply transmits the fire signal 4 times with a .1 second delay in between so that it gets 4 fire signals within a duration of about half a second per cue. There is sufficient time between cues that each cue has fully fired before moving on to the next one. Excellent idea though, I can see how it would work well if we were firing multiple effects within an individual cue. Gotcha. So you just programmed it to hammer the channel multiple times to overcome the "sometimes it does, sometimes it doesn't" problem. Not a bad way to work around the problem, particularly if cue latency is still OK with this method. |
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Another update. Removed the amplifier from the system, re-programmed the cue stack with a .1 second delay before sendInc multiple fire commands instead of what appeared to be a burst of multiple commands, and thus far haven't had any problems here in Long Beach. Ah! Very good point! Bet this fixes it permanently! Sometimes you can't see the forest for the trees. Johnny––thinking about this some more, which is difficult because I don't have the data sheet on the programmable controller and I'm making a number of HUGE assumptions, but I bet that the controller, which probably can fire truly simultaneous channels, doesn't realize that the TM16 cannot, i.e. I'm making an assumption that the TM16 can only fire one RF channel at a time. You need to give it time to transmit the firing data command for each channel. So it you've got pyro on 4 channels of your TM4 and you need it to all go truly simultaneously you need to move it all onto a single TM4 channel. Not the case. Not how the show fires. Only 1 channel on the RX-4's is utilized at any given time, no more than one effect fires consecutively within an individual cue, it simply transmits the fire signal 4 times with a .1 second delay in between so that it gets 4 fire signals within a duration of about half a second per cue. There is sufficient time between cues that each cue has fully fired before moving on to the next one. Excellent idea though, I can see how it would work well if we were firing multiple effects within an individual cue. Gotcha. So you just programmed it to hammer the channel multiple times to overcome the "sometimes it does, sometimes it doesn't" problem. Not a bad way to work around the problem, particularly if cue latency is still OK with this method. Pretty much. So far it's been ok, only had 2 FTF last week in Long Beach. Vegas this week, CES is here so I'm sure I'm being irradiated even as we speak so we'll see how it goes. |
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As others have pointed out, my guess is that the amp was causing saturation. Most amps work decently well just outside their band, generally with slow gain fall offs, not "it works or it doesn't".
The gain difference between your directional and omni will probably be around 8dB or so. At low frequencies, directionality is rather poor unless you have massive antennas. If you think 8dB of improvement will help, go for it. I'm guessing since your Tx and Rx are only a hundred feet away or so, you probably are fine with the a pair of omnis, as long as there aren't large salt bags (sorry, I mean people) directly in the way. Hope your problem has been solved. |
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Johnny––how are things working? Going ok so far. Was concerned a there's a big cell tower right across the street from the Thomas & Mack, and it's on the UNLV campus so there's lots of stuff flying around, not to mention it's almost directly in the approach pattern of McCarran. This far it's been ok though. I'd still like to see if I can get someone out with a spectrum analyzer and get some real data on it. I don't know how much removing the amp has accomplished but annecdotally it seems to have resolved the issue. Now if PyroPak would quit screwing up their matches it would be perfect. On another note, this has gotten me interested in getting my HAM ticket at least for the learnin' so hopefully my name will be in the 2012 thread! |