glenn

Zaxcom ZHD vs XR Modulation update

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Over the last 4 months we have been collecting data and real world experiences from our customer base and I wanted to post some thoughts on what we have learned. Zaxcom ZHD wireless modulation was introduced at NAB2016. The purpose of the new modulation was to significantly reduce the needed spectrum necessary for wireless microphone operation while maintaining like a hard wire audio quality. The goal of 100KHz channel to channel operation was achieved. It was also a goal to do this with currently FCC approved transmitters that would not require any modification going forward. This allows any customer that purchases Zaxcom gear today to be secure in the knowledge that this hardware would be usable for many years to come no matter what possible FCC rule changes might be in store. This goal was also achieved.

In the process of designing the high density system changes to the modulation had unexpected differences from our XR modulation relating to operating distance. There were many comparison tests done that were producing range differences of up to twice the range of XR modulation. There were also tests done that showed no increase in range over XR. So after some time here is the rule of thumb that should be used when selecting modulation when channel to channel spacing is not a factor.

XR is our most easily decoded modulation when no reflections or multi path are in play. (IE corn field in Iowa). XR only requires about 7 dB above the RF noise floor to decode. So in a RF quiet environment when reflections are not relevant XR is the way to go.

ZHD48 is a better choice when reflections are in play. City streets, mountains, dumpsters ect. can cause reflections that cause dropouts. ZHD will handle this type of interference and provide better range over XR in this type of environment. ZHD requires about 10 dB of signal over the noise floor. While this is not as good a figure as XR the multi path interference can easily make ZHD48 much easier to decode in a reflective environment.

We have recently introduced a new modulation called ZHD96. This new modulation is in the middle of XR and ZHD48. Its purpose was to keep the transmission audio latency down to around the 5 ms range so broadcasters can use our systems with IFB while maintaining a 200KHz channel to channel spacing. We expect the transmission characteristics to be some where in the middle between our two other modulations. 

As we move forward with our software defined wireless system we will continue to improve on our current technology and build quality. Thanks to all of our customers who use our products and give us feedback to help us make better products.

 

Glenn Sanders

President Zaxcom Inc.

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Idea: make modulation selection accessable via ZaxNet, on the fly. Otherwise who has time to try out different modulations in different environments.. or inevitably you forget which pack is set to what and want to change it after it's already on talent.

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Modulation needs a reboot.

I wonder if the premix from the new Deva can be added to nomad to compensate for the zhd48 latency...

It would be a great thing. Predelay.

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30 minutes ago, Derek H said:

Idea: make modulation selection accessable via ZaxNet, on the fly. Otherwise who has time to try out different modulations in different environments.. or inevitably you forget which pack is set to what and want to change it after it's already on talent.

I don't think the availability of several different modulations was ever intended (nor even possible) to select on the fly. Having different modulations in the same transmitter (hardware) helps to future proof the system, at least that's the way I see it. Most everybody will probably discover what works best for the types of jobs/environments you find yourself working in. 

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What is predelay? You can delay analog channels (but not digital, I think) on Nomad this is what I've been doing for years with my wireless. 

Would a timecode stamp shift in fractions of a frame be sufficient to have your mix be "real time" in relation to your delayed boom track?  

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Just out of curiosity, 

why available recording time in the MicroSd is affected by the chosen modulation?
And then, why Mono/ Stereo give less recording time than XR/ ZHD?
 
Attached is a screenshot from the LA3 user manual.
 
Vale.

Modulations.png

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On ‎9‎/‎9‎/‎2016 at 8:11 AM, RScottATL said:

What is predelay? You can delay analog channels (but not digital, I think) on Nomad this is what I've been doing for years with my wireless. 

Would a timecode stamp shift in fractions of a frame be sufficient to have your mix be "real time" in relation to your delayed boom track?  

Zaxcom revolutionized the technology by utilizing the buffer...Think  Prerecord .

Using the same technology I imagine an analog or AES channel where you can select the latency of the modulation to be compensated in the recorder sampling.

I spoke to Glenn about it.

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16 hours ago, vale said:

Just out of curiosity, 

why available recording time in the MicroSd is affected by the chosen modulation?
And then, why Mono/ Stereo give less recording time than XR/ ZHD?
 
Attached is a screenshot from the LA3 user manual.
 
Vale.

Modulations.png

It has to do with the way the data is processed for transmission for the different modulations. 

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On 6 September 2016 at 10:01 AM, glenn said:

We have recently introduced a new modulation called ZHD96. This new modulation is in the middle of XR and ZHD48. Its purpose was to keep the transmission audio latency down to around the 5 ms range so broadcasters can use our systems with IFB while maintaining a 200KHz channel to channel spacing. We expect the transmission characteristics to be some where in the middle between our two other modulations. 

 

Hi Glenn,

I have a combination of Block 20 4900 QRx100 rx 900 and TRX900 with mic plexir 1. I also have QRx200 x 1 and 742.5 and 743.5. I am about to add ZMT x 2. If I use ZHD 96 can i still use my qrx 200 in dual mode and will the plexir work with that setup in conjunction with running my block 20 TRxs all at the same time. Provided they are all within the 35mghz? I have a job in Asia coming up and in my experience there the RF varies a lot within a small space in the big cities. So i may need to use ZHD and utilise the reflections when amongst buildings but only can do that for the ZMT and 743 whilst running the rest in US mono. Its a bit confusing for me when mixing ZHD with US mono or should it be.

Is that the way to go? 

Another option i have thought about is to get the ZMT and extra qrx200 in the 3.6 band and have options either end of the spectrum but that means maybe an extra plexir and extra shark fins, getting really complicated now. Personally I have found better range when i run my qrx200 with other receivers through the plexir than if it was just a qrx200 on its own. Is this what you would expect?

I am new to the ZHD experience.

Anyone with experience mixing the various transmissions i would like to hear from. Also does the ZHD 96 make a BIG difference to range. ZHD 48 is not an option due to latency.

Many thanks

Tony

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You seem to be confusing RF with modulation schemes.  The Micplexer is an RF distribution amp and it has nothing to do with what modulation is being used. 

As far as mixing and matching modulation schemes, just make sure each transmitter and receiver pair are set for the same modulation.

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what john said.

also if you are using different modulations together think about the different delay.

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Sure I was just wanting to know if you can have successful blending of the old TRX with its requirement for larger channel separation with ZHD working in the same 35mghz and whether anyone has used the ZHD96 and experienced a significant increase in range. Personaly i have found negligible difference between US mono and XR so Rado i think you have tried the ZHD modulation. As you can imagine if you have several different modulations across different eras of zax it can get tricky if you want to chop and change tx with rx you will need to reboot etc and some won't work with others. Just trying to get the most out of having 8 yrs of zax wireless working together. 

Tony

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in my experience with my setup XR is enormous improvement over USMono. Zhd96 is on par with XR but behaves a little different with reflections. Zhd48 can be a little better then xr and zhd96 but it depends on reflection.

honestly the range improvement has to do a lot more with the RX antenna setup a lot more then what modulation is being used. 

 

as far as blending different modulations xr and zhd96 work fine together. Other ones not so much. 

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Just now, RadoStefanov said:

in my experience with my setup XR is enormous improvement over USMono. Zhd96 is on par with XR but behaves a little different with reflections. Zhd48 can be a little better then xr and zhd96 but it depends on reflection.

honestly the range improvement has to do a lot more with the RX antenna setup a lot more then what modulation is being used. 

 

When you say behaves different with reflections do you mean zhd is better with reflections? To be honest when i have switched to XR from Us mono i see better range on the meters and it does, at times, improve but usually the drop outs still occur. Maybe its something else it just doesn't seem the cure i was hoping for. Rado tell me about your antenna setup, any secrets? I use zax shark fins with a max length of 8 mtres 50ohm beldon low loss cable into Plexir. As stated earlier i believe the plexir gives me better range over straight out of a qrx200.

 

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45 minutes ago, Tony Johnson said:

 

When you say behaves different with reflections do you mean zhd is better with reflections? To be honest when i have switched to XR from Us mono i see better range on the meters and it does, at times, improve but usually the drop outs still occur. Maybe its something else it just doesn't seem the cure i was hoping for. Rado tell me about your antenna setup, any secrets? I use zax shark fins with a max length of 8 mtres 50ohm beldon low loss cable into Plexir. As stated earlier i believe the plexir gives me better range over straight out of a qrx200.

 

Plexer holds the signal longer. I have similar setup on the cart and lector dipoles in the bag.

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