In this video Stephen Pavlik walks me through how to create a link budget to find out if my wireless microphone system will work…or why it didn’t work.
There is no single point solution.
Every point in the RF signal chain can either attenuate or amplify the signal. If it goes too low, we get dropouts. If it goes too high, we get overloads. Through maximizing efficiency at every point, we can avoid dropouts and quickly troubleshoot interference.
Don’t be intimidated! There is no difficult math. The only challenge is researching the loss or gain of each piece of equipment in your signal chain.
This transcript was generated automatically. Please let me know if you find any errors.
Stephen, what are we doing here?
All right, so one thing that’s extremely important about RF is your gain. Your gain throughout the entire system, your gain coming out against into the gain, you lose going through air, essentially. And we need to be aware of all of that. And there’s a way we can actually calculate this to say, is this enough power? Is this system going to work?
We get an idea instead of just guessing, which is something we don’t really want to do except leave us uncomfortable, not confident. And then just that leaves us sweating behind the console saying maybe, maybe it will work.
So here’s a way that we can get away from that and feel confident that we notice it’s going to be going to be a good thing.
So from what you just said, I’m understanding that a link budget has to do with gain staging. Is that correct?
Yeah yeah. We’re we’re basically taking account for all the pluses and minuses, all the losses and all gains, whether active or passive, the entire system, and adding up to see what we get at the end.
Cool. So budget is like thinking about how much money I have to spend for the month. And link is each link between each device. Right. Each step in the signal chain. Yeah. OK. You made this info graphic and I think that infographics should sort of be self explanatory. And so what I would love to do is tell you about the things that I understand, the things that I don’t understand. And then, you know, other people watching this video as well will be able to ask questions and make comments on the video.
OK. So, first of all, all numbers to be in decibels. OK, great. So I’ve got to start here and then I’ve got to finish here at the bottom. Right. And this is some kind of a chart. So far, so good. So far so good. Okay. This is great. I’ve got a microphone here and t x means transmit. So the first step in my equation, I guess, is transmit power plus and ten a gain.
So I’ve got it. That’s my very first number, right. Yes. OK. And I guess I should go ahead and say that after we talk about this graphic, we actually have an example. So we’re going to talk about it in kind of an abstract way, not abstract, but we’re gonna talk about the method and then we’re going to apply the method, right? Yes. OK. Transmit plower plus antenna again. So this is where on my wireless microphone I can set normal high low power.
Or sometimes it’ll say like 10mW or 20 milliwatts. Right?
Absolutely. So that would be your transmitter power. Your TX power at that point.
Right. OK, so find out first and then this minus symbol here means that going to the air to the receive antenna, I’m going to have some loss. Yes.
Yeah So, yeah, minus going into research path loss, which is going from the microphones antenna to receive incentive. We have quite a bit of loss and that is really the wireless link. That is that is the wireless section. All right. OK. And I know that because I looked at this a little bit earlier, I saw this note down here in the bottom does not include miscellaneous losses like body loss feeding or antenna mismatch. Watts body loss.
Safadi loss is pretty much just what it sounds like. Our bodies absorb a lot of RF energy. And so if, for instance, I have a microphone right here on facing the antennas behind me, I’m facing away from it, I’m going to have lost from that. The reason I didn’t include it necessarily in a simple graphic is that it’s incredibly hard to predict. A lot of times we’ll throw a number in there for that. We should we can go over the example, but it’s it’s per basis type situation.
And so it’s not something I want to just throw in here. It’s just I don’t say it’s more for advanced users, but it’s something that we need to walk on and more deliately than than the rest of this, which is the straight forward portion of the budget.
Got it. So sometime in the future, there might be a whole other info graphic that’s just body loss. Yeah, that actually be great. OK. OK. So the signal gets from the microphone through the air to the antenna. But it looks like I’m jumping the gun a little bit here because the intent is down here. So the first step is actually how much loss in the air. That’s what this graphic part is. Oh, I see.
I see now. So it’s from intended to antenna. And we can actually calculate how much loss by I need the distance in meters and the frequency and megahertz so far. OK. So I would measure that distance with a disc, you know, measurement disto. I guess if I’m looking at a room diagram like the day before the event or I’m doing a site survey, I would look at the potential distance from like the farthest place on stage to wherever I plan to put my tennis.
Yeah, and a lot of times when we do these, we are looking for the worst possible case scenario. So if you know, there’s a point that you’re speaker or your artist might walk to pick the farthest region they physically go to into your worst case scenario and then anything else under the earth will be covered. So we’re trying to come up with a conservative figure here. Absolutely. OK. So we’re travelling through the air. We’ve calculated that with this step here in the frequency and megahertz says whatever the transmitter is gonna be set to.
Right. So I would have had to have done my coordination ahead of time. Or is there a conservative estimate for that as well? Because I might change the frequency during the show. If there’s some problem or once I get on site, I can tell you just the experience of changing the frequency in this formula.
It doesn’t change too much. But it’s good to keep it consistent, isn’t it? Each one you input is fine. Or if you want to take the tuning band of your particular type of gear and pick a frequency right in the center and use that as a reference exit, it doesn’t change too much. It’s mainly the actual distance. But, you know, it’s up to you. How do you want to get. I like to go dead on every time.
I like to find the figures I’m using. Exactly. Just to get as close as possible. Got it. Got it. So that this number here, the distances meters, is going to make a much bigger change than the frequency and megahertz. Yes, OK. Polarization mismatch. This is gonna be a loss. And you and I talked about this a little bit ahead of time because we’re trying to figure out how to show because polarization is basically antenna aim.
So if I have an L PDA that’s vertical and I have this incentive vertical. These are massive polarization. But if I have this at 90 degrees from my old PDA, you can see that this is political. Then I have a mismatch. Theoretically, 90 degrees off is an infinite mismatch. That doesn’t necessarily happen to free space. But so we need to add that in. Because there is always polarization, mismatch, loss. This is something that can be difficult to calculate because reflections.
But, you know, we can always say that we have men with TV. So if you watch the previous video, we talked about our Heligoland Center, which has a circular polarization. There is an actual fixed 3-D being mismatched. Lots of circular polarization now on linear incentives. If you have it. Forty five degrees. That math actually works out to three TV, which is why you see people trying to do the 90 degree angles on their tennis.
That’s exactly why. So say that they always have at least three TV position mismatch lost. And if you really have your antenna angled farther than that, for whatever reason, you can put it mean like that.
Now, this is making me wonder as well every time I put up my PDA. Shark fin intent has always put its vertical straight up and down. Are there ever times when you would want to do something different? I’ve never seen anything different. Yeah. So if you actually have your microphone, if it’s a microphone, it’s on a stand. It’s always going to be like this. Does it talk you into it? You would actually get better signal if you put your inside out or something like that.
If you don’t know it again. Forty five degrees. Because you’re, you know, you’re halfway in between. Vertical horizontal is gonna give you that sticks not fixed but close enough to fixed 3dB of mismatch. Which again is why I like we’ll do the 45 degree angle. But if you know this you can be fixed in one location and one orientation that if you put your receiver into the net orientation of the shot of getting the signal. Got it. OK.
Yeah, that’s really good to know. Now I’m trying to think about like, what adapter do I need from a mike stance and I can turn my antenna forty five degrees when you’re going out and you’re working on shows. How are you deploying your antennas? Are they angled like that. Yeah, I’m using LP claws so they can be…
LP claw onto a mike stand. Oh what one on a light and one on a rack. I move my antennas around all the time. Yeah. Just like your P.A.. You wouldn’t put it in the same. You wouldn’t say my P.A. always goes in this spot in every room I ever walk into.
OK. This is great, I’m learning a lot. So moving along here, we get to antenna gain and. OK, now I’m a little bit confused. Is this going to be a plus or a minus, or are we saying here that it could be either plus or. So this is going to be a plus. So we’re moving directly from polarization mismatch, right. Or the incentive. We’re going to be adding the incentive gain. So this next step is going to be a positive because the incentive gain should always be positive.
If not zero. We shouldn’t have negative in our field. It can’t happen. There’s some there’s we don’t need to dive into that. OK. We’re pretty much always going to have positive gains from this. And that’s passive gain as we’ve talked about incentive patterns. I’ll use this as an example again. This is going to be your cardio because you’re not radiating this direction right behind it. That radiation that is coming out this way is force forward. And so that is our passive gain.
Which this is about seven DB. So at that point, you use this little green plus here to add seven to our our budget. Got it. OK.
So your like shark fin PDA antenna might have 70 again. And then the, you know, standard omnidirectional antenna that came with your receiver should be passive and only directional. So it should be zero or close to zero. Close to zero two zero or four. I hold two point one five. OK. OK. So we picked up some gain with the antenna. Now we’re gonna lose some gain because of the cable and connector from the antenna to your multi-color gain or loss.
Right. Why do we have a negative here and then a plus minus here. OK, so that negative is going to last for seeing into the cable and so cables are always going to have a loss. You can put an amplifier on them, but you’re generally using amplifier to compensate for cables. Every single cable exhibits loss. In this instance, the cable from the incentive to the multi-color, if you’re not using a multi-color, if you don’t have multiple net, that would go straight to the receiver.
But the antenna coming out of the the cable community instead of joining the longest one in your system. So we need to figure out what kind of cable that is and what kind of loss associated with it and subtract that from our our system.
I’m seeing so. I see, so some of these things are. Equations that we can plug in, numbers to like up here and over here, and some of these things are just set by the manufacturer. We just look at the specification sheet and we say, OK, we have our G eight X cable or whatever. And that has this amount of loss per meter per foot. We see there are cables 10 feet long and then we know how much loss this is.
And you also mentioned Connector, though.
I do, and each should get out. How significant is that? I guess I could also look at the specification sheet for that connector. Yes, in that. So cables and the cables do break down over time. So you can look at specification sheet for whatever connector you have. Good connectors should be either no loss or point five, which is what I’ve put in these coming up. I put in those connectors. They’re broken down over time. Can be like one to one point five, hopefully not over that.
That’s pretty much broken. Cable connected, but also same with cables where they get broken out of its findings that the more loss.
OK. And that’s probably that’s a whole other thing we could talk about is how cables break down over time and how they are less efficient over time. So I guess we will dive into that now. But but that’s that’s a big topic, right? Yeah. That’s who we going to be and spend a day on that one. OK.
OK. So, Multi-color, what is a multi-color. Why don’t you just saying intendant distro or something like that.
Well that covers the generic terms that could be input or output. So the district that we’re familiar with was going to be our splitter, but generally referring to an active splitter. So in this sense, because we’re talking about a microphone, it would be a district or splitter. So we have one cable coming into it and that cable is split out two, maybe four, eight or however many that goes into multiple receivers. And also, in this instance, this is gonna be a unity gain device, which means that for each let’s say, if you have a split, just putting it two ways, we have three DBS.
You’re going to have the three TV amplifier to compensate for that to get you back to zero at the output. So if you’re using an active distro, which is what a lot of us are, then we’re going to have no loss in that and no gain on the Destra side. If you’re using a passive one, like a sure way to 21 or a Wilkins’s so or any kind of passes, but not A, B and C, T, that’s important that you will see about three, three point five to be lost there.
So if you are using a splitter or multicolor, it’s important to know what kind of it is and what kind of loss has associated with it, because we’re going to subtract that from it or we’re gonna leave it alone because theoretically has it is compensated for the loss it creates in itself. And is that why I didn’t. Know why I’m not a minus? I’ll get great. Yeah. I don’t get it.
So another potential loss here. Same same thing. Cable, last connector where you talked about that. And then we get to the finish line here. And now we have these numbers. Negative 40. Negative 70. Negative 90. Yes. And and the the colors mean anything. So as negative 40 good and negative 90 is bad.
Yes. This is something I want to talk about and specify a little bit. So negative 90 is definitely bad. A lot of receivers are using the noise floor is close to negative one hundred DBI or DVM. That’s not necessarily the lowest they can pick up. Let’s say if it’s negative 100, it doesn’t necessarily mean you could pick up a single negative. Ninety 90. So we want to stay away from anything getting close to negative night, especially because in this example, we’re not we’re not including his body losses yet.
And so we want to get as high as possible. Now, negative 70, I put his yellow because it’s definite acceptable. So the highest level you see on mostly receivers out there for sure, Sennheiser is around negative 70. Now, the high student go pretty much it’s getting close to negative 40, which is going to be close to peaking. But that’s that’s a good amount. Very, very strong about a signal. And so I put that in green, because if you have negative 40 with this example, let’s say we add in body loss, not chop this down a negative 60, which puts us above negative 70.
So we’re still going to have a very strong signal. So those are kind of examples that put negative 70 is absolutely workable. But we’re going to start getting some areas where if you get too far away or something happens, the change somewhere, you could have some issues. Maybe not. But Nago, 70 70s safe above that is great. We’re just getting above negative 40. Maybe not too much, but with losses. It’s hard to get that way unless you’re right up next to an attendant.
Or do you have some sort of device boosting it, possibly legally. So that’s kind of why the red and yellow and green. Got it. OK. So first I was thinking this didn’t make sense because all I really care about is getting is my relationship to the noise floor. But now you explaining that a lot of times the noise floor is around negative one hundred for many devices. Then now it makes sense that, OK, I need. I want to be above that at least like 50 DB, right.
Yes. 50 is great, except 40 is great. But you start getting a little too high. That negative 30 is kind of pushing it. But again, you can pull nego 30 out of this formula. But then just remember thinking about they’re going to have some walls with bodies.
And the whole goal, I guess we should have said at the beginning with this link budget is that we want to hit the target. We want to hit the bull’s eye. We don’t want to have so much gain that we have overload that we don’t want have so little gain that we dropped into a nice floor. Go below where squelch takes over and we have a drop out, right? Absolutely. And that is the goal. And does that have to do with my colors here?
So where do I hit an overload? Is that at zero? No, it is going to be around negative 30. Negative 20. OK. But again, even if you pull out negative 40 from this formula, we’re going to see more losses in the actual acquirement. So you’ll be safe with around negative 40. With with what we’re looking at, with the actual path that we have in this graphic. Great. OK. Thank you for explaining all these steps to me.
If you are watching this video right now and you have any questions for Steven about how he created this graphic, then please comment below. But we’re not finished yet. We’re actually going to go into the next page, which has an example. I just wanted to take a short break here and let you know that you can ask questions below this video. And Steven will do his best to answer them for you. As you can see, like we are trying to simplify something that is very complex and each one of these steps could have a whole video about it.
So ideally, I want to do this before a show, but I, I could see how would also be helpful, like doing a post-mortem. So after a show where I had problems, I could look at all the chain and say, OK, here’s maybe where the problem lies.
And actually real quick on that. I had that situation happen not too long ago where I had a system that had quite a bit of loss, but it was still going to make it. But I had an expected amount of loss with the cables in the Senate to Mike Binder on an I side. And it actually did cost drops. And going back to the system, I realized there is way too much loss of the cable and that I’m at a loss in that cable actually killed my shot a clean air show and swapping it out is what makes it so.
Yeah, you can you can deftly do it on the backside when the problem is happening, go through Jega everything and say, oh, that’s what it was. So yeah, this is helpful. Malloys. Walk me through this. It looks like we’re going to apply brand and model numbers to each of these steps in the chain. Yeah, absolutely. And right now, because we’re in twenty nineteen, I decided to use a you will see four trends but was trying to figure out what I wanted to choose.
And this one of these exhibitors will go at this one. And I think a lot of we’re starting to get into these. So we’re gonna go walk through this step by step with our you will see microphone up here. I kind of put up a situation ready to go by. So we had you like Steve for Transmuter 20 milliwatts, which is a high quality microphones I powerboat. We’re at five and a 40 megahertz, which is at shows up and it’s almost dead.
Center of the spectrum were allowed left and UHF, which is four seventy six or eight, not including garbanzos duplex steps, which is something else we can talk about in other lessons coming up. Maybe and we have 40 feet in 40 feet. What that means is from intended to antenna from the microphone to the receiver inside us, that is our actual wirelessly. So we have forty five degrees of polarization, mismatch loss. So that means we have our antenna like this, which is what we see and what we’ve talked about a little bit.
You watch less videos. And then we have an LAPD type in center. So we’re going to look at that and we’re just setting of gain seven. DVR. You want to be more specific. And then we have 30 feet of already eight X cable in which in this situation. Thirty feet of cable, which is frequencies specific, 540 megahertz equates to two point eight DB of gain. Sorry. Of loss. And then we have I just put in for a nice newish connecter point five DV connect the loss.
And then we’re gonna go into Internet distro or multicolor which is active. We’re going to have zero to be lost there. And then we’re going to our little short jumper from that inside the rack from our multi-color to our receiver, which because it’s quite smaller. We can see the head lost, dropped quite a bit negative. Sorry to two point eight point two eight TV. Those points are hard to see there. Yeah. Then we have another connector.
Lost a point five and then we end up back at our receiver with our final signal level.
So, wow. OK. So then you added those all together here at the bottom with a final level of negative thirty point three DB at the receiver. Yeah.
And so looking at that, that guy to the right with the red negative 90, yellow negative 73, negative 40. So we are above that negative 40 with negative thirty point three. And in some instances that negative 30 could mean an overload. But we didn’t do. Here is a Audy loss and other environmental losses. So. All right. An absolute minimum of at least 20 stat, which is a negative 50. So we’re totally fine. And one thing I do want to talk about real quick is how do we figure out gain from a microphone and said we can definitely look at specs like this.
Right here is a fresh wireless system that I can look on their Web site and I can see how much gain they sense. You’re talking about this stuff here, right? Are X and 10 a gain?
Yeah. And actually kind of going to the actually the Texans in a gain. So, I mean, just as a reference, that antenna just showed us, we can look up the Web site and they’ll tell us what gain to ask. But how do we know the gain of a microphone? Right. It’s hard to predict. And one thing is, I don’t know. You just tell me. Twenty no lights. Oh, that’s the transmitter per gain.
So every antenna is going to have some sort of gain or not. And so where I’m using zero DB for this antenna because it has actually a normal. This is. This is a normal motor vehicle on it. There’s actually a huge advance and I believe it’s a. You see four other omnidirectional. So they’re not really having for a gain. And so I’m using zero for that. OK. And that’s something I do want to point out because that’s a question.
How do we figure that Kane number out? And there’s really not there. You could use one if you want me to be more typical of a whip on a body pack. But it’s a good safe bet to use to zero and a gain for a microphone.
OK. Why does this say 13 in this says 20? All right. So that is our conversion to DBI. So if you notice in the top right, all numbers are to be NDB. If we actually make that mistake, do one in milliwatts, we’re going to get a funky number. That’s not to be accurate. So we need to make sure everything is in DBI for this for this calculation. So how did it how did you get from 20 milliwatts to 13 D.V.?
All right. So we take a lot of money and then it. Wait. Say that again.
Log base 10 of 20 and then multiply by 10. 20 million watts. Yep. Log ten times ten. Again, we get 13 D.V.. OK, great.
And that’s a good one to memorize because we do most things in DBI as engineers and in all fields of audio.
Are a DB as a friend. Great. What I think it is pretty clear. And then in the end, you just add in all those numbers up and got your final number and you said, hey, negative 30. That’s good. That’s up into the green number, right? Yeah. So we’re gonna we’re going to we’re going to assume more lost in that. And we have that much power getting that negative 40 region that we’re also going to put.
It’s still a very good area. So anywhere around that green. And we’re good. All right.
So this is a lot of stuff. I know we went through this really quickly. I would love to see your example of a link budget for your next show or Pashto that you’ve done. And if you want to, you know, draw it out, take a photo of it and posted here along with this video. You know, we can we can see if we can get Steven to look at him and see if he thinks they’re correct. If you estimated well and you know, some of this stuff you can grab.
So if you’re using a ULXD receiver, you can use the numbers that we used in this example. Otherwise, you know, you have to look up each one for your specific situation. But, Steven, thank you so much for putting this together. And now I obviously need to practice it to practice doing it myself. Awesome. Thanks for the opportunity. This is great. Hopefully everybody takes a shot at this and has good results.