What do you consider best practices for setting up paddle antennas for a diversity receiver? Spacing, placement, etc.?
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Best practices for paddle antennas and diversity receivers?
- Thread starter Jay Barracato
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Re: Best practices for paddle antennas and diversity receivers?
Broadly - line of sight to one or both, and over head height.
We often have do left and right sides of the stage, it varies on stage and room layout, if there will be a roving audience mic, etc
Broadly - line of sight to one or both, and over head height.
We often have do left and right sides of the stage, it varies on stage and room layout, if there will be a roving audience mic, etc
Re: Best practices for paddle antennas and diversity receivers?
Ten feet apart as best practice, no less than two feet apart for UHF (approx. one wavelength) under any circumstances. Mounted as high as possible overhead to reduce the likelihood of 1st Fresnel zone obstructions along all line of sight signal paths.
Fully overlapping axial gain pattern coverage over the entire performance area.
Orienting them tilted 45 deg. off of vertical along their radiation axis, opposite of each other, can help to mitigate dropouts caused by polarization mismatch losses, but be mindful that this narrows their axial gain pattern in azimuth.
Ten feet apart as best practice, no less than two feet apart for UHF (approx. one wavelength) under any circumstances. Mounted as high as possible overhead to reduce the likelihood of 1st Fresnel zone obstructions along all line of sight signal paths.
Fully overlapping axial gain pattern coverage over the entire performance area.
Orienting them tilted 45 deg. off of vertical along their radiation axis, opposite of each other, can help to mitigate dropouts caused by polarization mismatch losses, but be mindful that this narrows their axial gain pattern in azimuth.
Re: Best practices for paddle antennas and diversity receivers?
Good Question!!
Solid Answer!
Good Question!!
Solid Answer!
Re: Best practices for paddle antennas and diversity receivers?
If you ever have a chance to hear Tim Vear from the Shure team speak, he does an INCREDIBLE training for RF.
Dave Missal from Sennheiser also offers great clinic presence.
Great to give you some fundamentals on what's what. Give you an idea of what you don't know.
I've met too many people having problems with RF dropout and interference from other nearby venues who have a pile of transmitters all turned on piled on top of the RF rack. I had someone argue with me that it couldn't be RF his mics causing the dropout because the mics weren't plugged in. Tim's demonstration of inter mod products made a great impression on me.
If you ever have a chance to hear Tim Vear from the Shure team speak, he does an INCREDIBLE training for RF.
Dave Missal from Sennheiser also offers great clinic presence.
Great to give you some fundamentals on what's what. Give you an idea of what you don't know.
I've met too many people having problems with RF dropout and interference from other nearby venues who have a pile of transmitters all turned on piled on top of the RF rack. I had someone argue with me that it couldn't be RF his mics causing the dropout because the mics weren't plugged in. Tim's demonstration of inter mod products made a great impression on me.
Re: Best practices for paddle antennas and diversity receivers?
Don't forget our pals Karl Winkler and Howard Kaufman from Lectrosonics, either, also extremely knowledgeable - and they advertise to support this forum!
All the above folks gave talks at the LAB get togethers here in MA that we did five or six years back, on multiple years, and were one of the highlights for me. These guys worked together even though they work for the three top competing brands in wireless and put together awesome presentations to educate attendees on fundamental but often ignored RF techniques.
Don't forget our pals Karl Winkler and Howard Kaufman from Lectrosonics, either, also extremely knowledgeable - and they advertise to support this forum!
All the above folks gave talks at the LAB get togethers here in MA that we did five or six years back, on multiple years, and were one of the highlights for me. These guys worked together even though they work for the three top competing brands in wireless and put together awesome presentations to educate attendees on fundamental but often ignored RF techniques.
Re: Best practices for paddle antennas and diversity receivers?
YES!!! Karl and Howard, making the big treks that they did. Of course. The roundtable was brilliant!
I keep waffling as to if we should do another one of those shindigs. What do you say?
YES!!! Karl and Howard, making the big treks that they did. Of course. The roundtable was brilliant!
I keep waffling as to if we should do another one of those shindigs. What do you say?
Re: Best practices for paddle antennas and diversity receivers?
SFN does have some money, which is nice since then neither of us would have to foot any overrun, but I don't have the time. Dave K and I were thinking about maybe hosting a 5th anniversary party at a bar for InfoComm or something, but that wouldn't exactly be a trade show.
SFN does have some money, which is nice since then neither of us would have to foot any overrun, but I don't have the time. Dave K and I were thinking about maybe hosting a 5th anniversary party at a bar for InfoComm or something, but that wouldn't exactly be a trade show.
Re: Best practices for paddle antennas and diversity receivers?
Bear in mind if you do this you will lose diversity, unless you are using a pair on each side of the stage.
Re: Best practices for paddle antennas and diversity receivers?
How so? The point of diversity receivers is to reduce or eliminate multipath issues and dropouts due to obstructions. One antenna on each side of the stage (assuming each antenna has full coverage of the stage) absolutely provides this.
How so? The point of diversity receivers is to reduce or eliminate multipath issues and dropouts due to obstructions. One antenna on each side of the stage (assuming each antenna has full coverage of the stage) absolutely provides this.
Re: Best practices for paddle antennas and diversity receivers?
Only if the antennas are covering different performing areas.
Mac
Only if the antennas are covering different performing areas.
Mac
Re: Best practices for paddle antennas and diversity receivers?
Clear this up for me, it is my understanding that to reap the greatest benefit from diversity the signal chain of the antennas must be the same. Same model of antenna, same gain setting, same cable length. I see a lot of installs and mobile setups that don't follow these guidelines....
Clear this up for me, it is my understanding that to reap the greatest benefit from diversity the signal chain of the antennas must be the same. Same model of antenna, same gain setting, same cable length. I see a lot of installs and mobile setups that don't follow these guidelines....
Re: Best practices for paddle antennas and diversity receivers?
For example, a viable arrangement could consist of a low gain antenna located very near the performer and a high gain antenna located far away. As long as both adequately cover the performance area, multipath dropouts on one antenna will likely not occur at the other simultaneously.
It's more about having the most efficient system possible on both sides. As long as one of the two has sufficient signal strength and CNR at any point in time, diversity will function correctly.
For example, a viable arrangement could consist of a low gain antenna located very near the performer and a high gain antenna located far away. As long as both adequately cover the performance area, multipath dropouts on one antenna will likely not occur at the other simultaneously.
Re: Best practices for paddle antennas and diversity receivers?
Thanks for the reply! I really appreciate it.
By "most efficient" what do you mean? What is a diversity receiver looking for? Highest gain? Highest SNR? A combo of gain and SNR? Wouldn't an extra 50ft of cable loss on matched antenna's potentially defeat the purpose of diversity by favoring the higher gain/better SNR antenna? Same for mismatched antennas? Is appropriately spaced matched antennas, gain, cable lengths the ideal setup or am I completely missing a core concept?
Thanks for the reply! I really appreciate it.
By "most efficient" what do you mean? What is a diversity receiver looking for? Highest gain? Highest SNR? A combo of gain and SNR? Wouldn't an extra 50ft of cable loss on matched antenna's potentially defeat the purpose of diversity by favoring the higher gain/better SNR antenna? Same for mismatched antennas? Is appropriately spaced matched antennas, gain, cable lengths the ideal setup or am I completely missing a core concept?
Re: Best practices for paddle antennas and diversity receivers?
It's a combo of sufficient received signal strength to open squelches and maintain optimal demodulation, and of sufficient CNR (carrier to noise ratio) to keep audible demodulated noise to a minimum. The signal path consists of not only the antennas, cables, and connectors, but also includes the free space between TX and RX antennas. This space is the highest loss component of the path, and it's constantly changing due to the distance between the TX and RX antennas, and it changes at the extremes caused by the inverse square law.
It's OK for diversity to favor the higher gain antenna/signal path. That's what it's supposed to do, and it's one reason why your diversity pair's axial gain patterns should completely overlap the entire performance area. The purpose of diversity is simply and only to switch to the side with higher RSS (received signal strength) and CNR when multipath interference occurs on one of the two in the pair.
It's important to realize that high gain and low noise in an antenna system has little bearing on multipath interference's frequency of occurrence or how much it will attenuate the signal at the receiver. It will occur when the TX or RX antennas in a link occupy a space that is also occupied by RF-reflective objects, and both antennas and/or objects are not strictly fixed to optimal positions. So, in a situation where the system has high gain on side A and low gain on side B, but both are sufficient for normal function, diversity may or may not favor A until an inevitable dropout occurs, when it will inaudibly switch to B until B drops out, and then switch back to A when appropriate, and on and on. The receiver and diversity systems usually don't care which side has stronger signal, as long as the one that they're using at the moment is sufficient for normal function.
It's a combo of sufficient received signal strength to open squelches and maintain optimal demodulation, and of sufficient CNR (carrier to noise ratio) to keep audible demodulated noise to a minimum. The signal path consists of not only the antennas, cables, and connectors, but also includes the free space between TX and RX antennas. This space is the highest loss component of the path, and it's constantly changing due to the distance between the TX and RX antennas, and it changes at the extremes caused by the inverse square law.
It's OK for diversity to favor the higher gain antenna/signal path. That's what it's supposed to do, and it's one reason why your diversity pair's axial gain patterns should completely overlap the entire performance area. The purpose of diversity is simply and only to switch to the side with higher RSS (received signal strength) and CNR when multipath interference occurs on one of the two in the pair.
It's important to realize that high gain and low noise in an antenna system has little bearing on multipath interference's frequency of occurrence or how much it will attenuate the signal at the receiver. It will occur when the TX or RX antennas in a link occupy a space that is also occupied by RF-reflective objects, and both antennas and/or objects are not strictly fixed to optimal positions. So, in a situation where the system has high gain on side A and low gain on side B, but both are sufficient for normal function, diversity may or may not favor A until an inevitable dropout occurs, when it will inaudibly switch to B until B drops out, and then switch back to A when appropriate, and on and on. The receiver and diversity systems usually don't care which side has stronger signal, as long as the one that they're using at the moment is sufficient for normal function.
Re: Best practices for paddle antennas and diversity receivers?
I recall discussions from the past where the definition of "diversity" was debated. For some it's all about mitigating multi-path nulls. For others it stands for more than that. Perhaps somewhere there is an official description of the term as it applies to wireless mics.
Two things that I think would be good to mention:
A) The behavior of mismatched antenna's (well, probably more specifically mismatched received RF level) depends on the type and flavor of diversity. Shure's system used in a few of their analog wireless systems picks the antenna based on the ultrasonic SN of the demodulated audio signal. And, it actually blends the audio from both antenna's together if signal is sufficiently good from both. Some diversity systems might look at absolute RF signal at each antenna as part or all of the antenna picking logic (polarity reversing diversity?). That said, it is my understanding that most receivers use some sort of auto gain at the beginning of the RF stage so differences in antenna gain (or cable loss) might be rendered moot. Lectrosonics has some [dated] documents that describe a few different methods of achieving diversity reception.
B) CNR is mostly what really matters. And CNR doesn't need to be particularly high, compared to what we're used to with audio, to get a good "link". 10db or so will usually do it. Now, you can't get good CNR if carrier strength is really low. But in most of our real world situations with wireless mics, low average carrier strength isn't the biggest issue. Instead it's things like multi-path, over-loaded receivers (transmitter too close to antennas) and intermodulation that challenge us.
As always, this is based on how I understand things. Jason please correct as you see fit.
I recall discussions from the past where the definition of "diversity" was debated. For some it's all about mitigating multi-path nulls. For others it stands for more than that. Perhaps somewhere there is an official description of the term as it applies to wireless mics.
Two things that I think would be good to mention:
A) The behavior of mismatched antenna's (well, probably more specifically mismatched received RF level) depends on the type and flavor of diversity. Shure's system used in a few of their analog wireless systems picks the antenna based on the ultrasonic SN of the demodulated audio signal. And, it actually blends the audio from both antenna's together if signal is sufficiently good from both. Some diversity systems might look at absolute RF signal at each antenna as part or all of the antenna picking logic (polarity reversing diversity?). That said, it is my understanding that most receivers use some sort of auto gain at the beginning of the RF stage so differences in antenna gain (or cable loss) might be rendered moot. Lectrosonics has some [dated] documents that describe a few different methods of achieving diversity reception.
B) CNR is mostly what really matters. And CNR doesn't need to be particularly high, compared to what we're used to with audio, to get a good "link". 10db or so will usually do it. Now, you can't get good CNR if carrier strength is really low. But in most of our real world situations with wireless mics, low average carrier strength isn't the biggest issue. Instead it's things like multi-path, over-loaded receivers (transmitter too close to antennas) and intermodulation that challenge us.
As always, this is based on how I understand things. Jason please correct as you see fit.
Re: Best practices for paddle antennas and diversity receivers?
I'm not the Jason you're looking for, but here's how I see it:
the weakest of the two antennas/signals still has to be functional across the whole area where the mic will be used (except for tiny nulls due to multipath interference)
It's no hit to performance if the receiver rides on the stronger antenna 99.9% of the time, as long as the 0.01% where it takes a hit the other antenna has a useable signal to fill the gap.
Since dropouts due to multipath are a factor of physical reflections and interference from other signals having a better antenna won't change much. Otherwise someone would have built THE killer antenna already.
Jason
I'm not the Jason you're looking for, but here's how I see it:
the weakest of the two antennas/signals still has to be functional across the whole area where the mic will be used (except for tiny nulls due to multipath interference)
It's no hit to performance if the receiver rides on the stronger antenna 99.9% of the time, as long as the 0.01% where it takes a hit the other antenna has a useable signal to fill the gap.
Since dropouts due to multipath are a factor of physical reflections and interference from other signals having a better antenna won't change much. Otherwise someone would have built THE killer antenna already.
Jason
Re: Best practices for paddle antennas and diversity receivers?
Blends like mix it?
If path lengths from TX to RX antennes do differ to much I would assume to much difference in latency, so giving problems when mixed in analog audio domain.
I can imagine that with the newer digital systems they can easilier sync both.
Blends like mix it?
If path lengths from TX to RX antennes do differ to much I would assume to much difference in latency, so giving problems when mixed in analog audio domain.
I can imagine that with the newer digital systems they can easilier sync both.
Re: Best practices for paddle antennas and diversity receivers?
RF propagates a lot faster than sound, so a latency difference of even one microsecond would correspond to a path length difference of 300 metres.
You obviously don't want to combine the received RF-modulated signals together, but combining the demodulated audio should be harmless enough unless path length differences are on the order of kilometres.
RF propagates a lot faster than sound, so a latency difference of even one microsecond would correspond to a path length difference of 300 metres.
You obviously don't want to combine the received RF-modulated signals together, but combining the demodulated audio should be harmless enough unless path length differences are on the order of kilometres.
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Re: Best practices for paddle antennas and diversity receivers?
Thank you to BOTH Jasons and Drew, I appreciate it!
Thank you to BOTH Jasons and Drew, I appreciate it!
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