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LarryF

Question about passive splitter for bag use

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Thanks for the guide Derek, I'll certainly take a look at it soon. Larry I believe I understand what you are saying, I know this is pretty basic stuff to you all but I'm just getting into the higher end stuff, so I appreciate everyone answering. Just when I think I start to really get a grasp on this stuff something new comes along. 

 

So to check on my learning here, one "shark fin" antenna cannot feed both inputs on the same SRc, but it can feed one input on two separate SRc's. 

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1 minute ago, Erob said:

So to check on my learning here, one "shark fin" antenna cannot feed both inputs on the same SRc, but it can feed one input on two separate SRc's. 

 

That is correct. You can use two different kinds of antennas, but you need two different antennas for sure. Two antennas, two splitters, into two receiver antenna inputs.

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5 minutes ago, Erob said:

...

Just when I think I start to really get a grasp on this stuff something new comes along. 

...

 

I've found that when one starts to learn about something, there comes a time when the new information makes one feel empowered, and it results in an "I know it now!" feeling.  That's the danger point. 

 

A hard acquired lesson is that the actual start of learning anything is when you begin to understand how much you don't know about it.

 

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3 minutes ago, John Blankenship said:

A hard acquired lesson is that the actual start of learning anything is when you begin to understand how much you don't know about it.

 

It's just a series of never ending bell curves...you get to the top in one then quickly fall to the bottom of not knowing the next thing and it just keeps repeating.

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1 hour ago, Erob said:

Thanks for the guide Derek, I'll certainly take a look at it soon. Larry I believe I understand what you are saying, I know this is pretty basic stuff to you all but I'm just getting into the higher end stuff, so I appreciate everyone answering. Just when I think I start to really get a grasp on this stuff something new comes along. 

 

So to check on my learning here, one "shark fin" antenna cannot feed both inputs on the same SRc, but it can feed one input on two separate SRc's. 

You've got it.

Best,

Lef

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Lets say I will use a passive 3 way splitter, but most of the time I only have 2 SR'S connected, leaving the third output on the splitter open for an occasional third wireless, lets say an LR. 
When not using the third output, there will still be a 1/3 loss, not a 1/2 right?

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3 hours ago, NickFriedrich said:

Lets say I will use a passive 3 way splitter, but most of the time I only have 2 SR'S connected, leaving the third output on the splitter open for an occasional third wireless, lets say an LR. 
When not using the third output, there will still be a 1/3 loss, not a 1/2 right?

Pretty much correct. Even if the third output is not terminated, a quality splitter will isolate the inputs. 

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Hello Larry,

 Can you explain, or direct me to published info, about how the SR series of receivers share the antennas between the two circuits?

 

 How does the SR design split the incoming signal and maintain performance comparable to the 411 series?

 

 Thank you.

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Thank you for the suggestion.

 

The block diagram shows a pair of splitters. One splitter per antenna. The descriptions speak of the diversity systems, and explain that two receivers can run independently while sharing the antennas in the SmartDiversity mode.

 

My question, which has been inspired by this thread, is directed at the technology of the splitter(s).

 

In other words, is it a passive splitter with signal loss, or is it active splitter with a "noise" increase? How did Lectrosonics achieve a level of performance comparable, or nearly comparable too, the 411 design with either a signal loss or noise increase? 

 

I had not appreciated the challenge that has been met until this thread caused me to think "wait a minute, the SR series must have on board splitters and all the gotchas associated with the use there of.".

 

How did they do that?

 

Thank you.

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3 hours ago, alenK said:

Thank you for the suggestion.

 

The block diagram shows a pair of splitters. One splitter per antenna. The descriptions speak of the diversity systems, and explain that two receivers can run independently while sharing the antennas in the SmartDiversity mode.

 

My question, which has been inspired by this thread, is directed at the technology of the splitter(s).

 

In other words, is it a passive splitter with signal loss, or is it active splitter with a "noise" increase? How did Lectrosonics achieve a level of performance comparable, or nearly comparable too, the 411 design with either a signal loss or noise increase? 

 

I had not appreciated the challenge that has been met until this thread caused me to think "wait a minute, the SR series must have on board splitters and all the gotchas associated with the use there of.".

 

How did they do that?

 

Thank you.

Hi Alen,

The 411 has the RF front end after the diversity phase switches because the phase switches have very low loss (1 dB). This a simple configuration. If we had put the RF front end before the phase switches, it would have added much complication for little gain (pun intended), requiring an additional amp and additional input filter set.

 

The SR's, however,  have the normal receiver RF front ends before the diversity switches and the antenna splitter. That is to say, the first RF amplifier stages each played the dual roles of RF front end and active splitter amplifier. This is because in the SR you would have that same 1 dB of phase switch loss plus the unavoidable 3 dB of loss in a two way splitter. Four dB is too much to give up. Luckily you have to have the two RF front ends and two filter sets anyway for the two receivers. Putting the circuity after the two amps and filters, added almost no complication to the circuit. Sometimes things work to your advantage.

Best Regards,

Larry Fisher

 

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Thank you for explaining. This information increases my appreciation of the SR receivers.

 

Thank you.

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On 4/21/2018 at 9:38 AM, LarryF said:

Hi Alen,

The 411 has the RF front end after the diversity phase switches because the phase switches have very low loss (1 dB). This a simple configuration. If we had put the RF front end before the phase switches, it would have added much complication for little gain (pun intended), requiring an additional amp and additional input filter set.

 

The SR's, however,  have the normal receiver RF front ends before the diversity switches and the antenna splitter. That is to say, the first RF amplifier stages each played the dual roles of RF front end and active splitter amplifier. This is because in the SR you would have that same 1 dB of phase switch loss plus the unavoidable 3 dB of loss in a two way splitter. Four dB is too much to give up. Luckily you have to have the two RF front ends and two filter sets anyway for the two receivers. Putting the circuity after the two amps and filters, added almost no complication to the circuit. Sometimes things work to your advantage.

Best Regards,

Larry Fisher

 

 

Larry - First of all thank you. This is my firs time posting, but I have been a follower of JW for years and your responses are 90% of the reason why. That being said, taking all of this info in your post... Is combing ENG bag Rx antennas for better / stronger range with an SMa Multi / Lectro Dipole when using a variety of 411s and SRs a difficult thing to do successfully because of the difference in hardware?

 

Also, not to hijack the thread but while I have the Lectro Lord himself - Is it possible to simplify a Hop Tx set up and just use one SM in IFB mode to send to R1a's for IFBs and 411a's in IFB mode for cameras (reality projects, scratch/reference tracks mainly). Basically is there a major difference in quality between 400 and IFB mode, or any other reason why that set up audibly wouldn't be ideal? I have a feeling the answer is yes there is a difference in quality due to companding when higher frequencies are involved?  

 

Thanks for your time. 

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An RF distro like the PSC RF SMA and a dipole will be beneficial for any kind of receiver, doesn’t matter what model. Mainly because you’re then able to use improved antennas and get them in a better position. This has been said a few times here in this thread. 

 

Yes, you you can use a single transmitter in IFB mode to transmit to both R1a receivers and   any other Lectro 400 series receiver (411/401/SR/LR) set to IFB mode. Or to a Sennheiser G3 with the pilot tone disabled for that matter. 

 

Lots of mixers just use an R1a on camera for scratch track with a 3.5mm to XLR adapter cable and tape the headphone volume knob down. 

 

 

Oh and yes 400 mode sounds better than IFB mode. 

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That wasn't my question. My question was when you have a combination of different types of receivers pulling from the same passive dristro / antennas. Ive done it with powered sharkies, but never a passive system. In a passive system, are the SRs fighting harder for signal over the 411s, etc. I understand the concept of using improved antennas and getting them up and out of the bag but have heard multiple people complain about issues when having both SRs and 411s in the bag with a passive system, just wondering if what Larry posted about difference in hardware layout internally has something to do with that. 

 

Also yes, im aware it is possible to accomplish that signal flow in IFB mode, I was asking for the reasoning / explanation / science behind it. Will the higher frequency say, when cast screams or yells, be affected in IFB mode on a 411 as opposed to in 400 mode and why. 

 

But thank you for your response, Derek.

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3 hours ago, Angelo C said:

<snip>... when you have a combination of different types of receivers pulling from the same passive dristro / antennas. Ive done it with powered sharkies, but never a passive system. In a passive system, are the SRs fighting harder for signal over the 411s, etc. I understand the concept of using improved antennas and getting them up and out of the bag but have heard multiple people complain about issues when having both SRs and 411s in the bag with a passive system, just wondering if what Larry posted about difference in hardware layout internally has something to do with that. 

 

Also yes, im aware it is possible to accomplish that signal flow in IFB mode, I was asking for the reasoning / explanation / science behind it. Will the higher frequency say, when cast screams or yells, be affected in IFB mode on a 411 as opposed to in 400 mode and why. <snip>

The passive splitters of good quality (Lectro or MiniCircuits) isolate the outputs from one another. The isolation is typically 20 dB and is much more than enough to prevent any "fighting" among receivers. The splitters also block garbage on one receiver's antenna ports from getting into a different receiver. The isolation is typically better than 20 dB. Since the garbage is usually very low, the 20 dB of attenuation mostly "disappears" it. In sum, use any combination of receivers that you want.

 

The IFB system uses a simple single compander circuit with pre-emphasis and has all the usual drawbacks of a simple. pre-emphasized analog system. In addition, the IFB system only uses 25 kHz of deviation due to the limitations of the IF filter system. This causes less FM suppression of noise. The IFB system also has problems with high level, high frequency audio such as rattling keys and strong sibilants  All this to say, the IFB system was intended for voice and confirmation of the program material. It has been used for more demanding work but still, it is not the best sounding Lectro system.

The 400 series running in IFB mode duplicates all the foibles and warts of the IFB system with perfect precision. I would say, use IFB emulation when you have to but realize it is not the best fidelity.

Best Regards,

Larry Fisher

 

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38 minutes ago, LarryF said:

The passive splitters of good quality (Lectro or MiniCircuits) isolate the outputs from one another. The isolation is typically 20 dB and is much more than enough to prevent any "fighting" among receivers. The splitters also block garbage on one receiver's antenna ports from getting into a different receiver. The isolation is typically better than 20 dB. Since the garbage is usually very low, the 20 dB of attenuation mostly "disappears" it. In sum, use any combination of receivers that you want.

 

The IFB system uses a simple single compander circuit with pre-emphasis and has all the usual drawbacks of a simple. pre-emphasized analog system. In addition, the IFB system only uses 25 kHz of deviation due to the limitations of the IF filter system. This causes less FM suppression of noise. The IFB system also has problems with high level, high frequency audio such as rattling keys and strong sibilants  All this to say, the IFB system was intended for voice and confirmation of the program material. It has been used for more demanding work but still, it is not the best sounding Lectro system.

The 400 series running in IFB mode duplicates all the foibles and warts of the IFB system with perfect precision. I would say, use IFB emulation when you have to but realize it is not the best fidelity.

Best Regards,

Larry Fisher

 

Larry my friend, you are THE BEST. Thank you for constantly explaining the science to us all! Your lessons are priceless. Thank you for your time. 

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54 minutes ago, LarryF said:

The passive splitters of good quality (Lectro or MiniCircuits) isolate the outputs from one another. The isolation is typically 20 dB and is much more than enough to prevent any "fighting" among receivers. The splitters also block garbage on one receiver's antenna ports from getting into a different receiver. The isolation is typically better than 20 dB. Since the garbage is usually very low, the 20 dB of attenuation mostly "disappears" it. In sum, use any combination of receivers that you want.

 

The IFB system uses a simple single compander circuit with pre-emphasis and has all the usual drawbacks of a simple. pre-emphasized analog system. In addition, the IFB system only uses 25 kHz of deviation due to the limitations of the IF filter system. This causes less FM suppression of noise. The IFB system also has problems with high level, high frequency audio such as rattling keys and strong sibilants  All this to say, the IFB system was intended for voice and confirmation of the program material. It has been used for more demanding work but still, it is not the best sounding Lectro system.

The 400 series running in IFB mode duplicates all the foibles and warts of the IFB system with perfect precision. I would say, use IFB emulation when you have to but realize it is not the best fidelity.

Best Regards,

Larry Fisher

 

Larry - Is a T2 built with better subsystems then say an SMa thats emulating? Would replacing the SMa in that system with the 411 in IFB mode make for a better quality with those high frequency issues?

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Hi Angelo,

I would say no to both questions. The digital emulation very accurately duplicates the analog IFB, including the short comings. 

Best Regards,

Larry Fisher

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