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Sound Reinforcement - Forums for Live Sound Professionals - Your Displayed Name Must Be Your Real Full Name To Post In The Live Sound Forums => Wireless and Communications => Topic started by: Andrew Broughton on March 13, 2018, 01:03:58 pm

Title: Combiner quality
Post by: Andrew Broughton on March 13, 2018, 01:03:58 pm
How do the following combiners rate in terms of signal quality?

Shure PA821A (https://www.shure.com/americas/products/accessories/personal-monitor-systems/psm-antenna-combiners/pa821a-psm-antenna-combiner)
Sennheiser AC3200-II (https://en-us.sennheiser.com/ac-3200-ii)
RF Venue Combine-4 (https://www.rfvenue.com/products/combine4)
RAD TX-8 (http://radioactiverf.com/home/products/combiners-splitters/tx-8-transmitter-combiner/)

I would assume the RAD TX-8 would be at the top of the list, but how do the Shure and Senn compare? Anyone done or seen tests on these devices? Are there any other quality products out there that I'm missing?

My application would be the using these with LectroSonics M2-Duet series IEMs but also possibly with Shure PSM1000/Sennheiser 2000 series IEMs.

Thanks!
Title: Re: Combiner quality
Post by: Bob Charest on March 13, 2018, 06:39:55 pm
How do the following combiners rate in terms of signal quality?

Shure PA821A (https://www.shure.com/americas/products/accessories/personal-monitor-systems/psm-antenna-combiners/pa821a-psm-antenna-combiner)
Sennheiser AC3200-II (https://en-us.sennheiser.com/ac-3200-ii)
RF Venue Combine-4 (https://www.rfvenue.com/products/combine4)
RAD TX-8 (http://radioactiverf.com/home/products/combiners-splitters/tx-8-transmitter-combiner/)

I would assume the RAD TX-8 would be at the top of the list, but how do the Shure and Senn compare? Anyone done or seen tests on these devices? Are there any other quality products out there that I'm missing?

My application would be the using these with LectroSonics M2-Duet series IEMs but also possibly with Shure PSM1000/Sennheiser 2000 series IEMs.

Thanks!

Hi Andrew,

Currently using the Shure PA821A with no complaints. I'd tried the Sennheiser AC3200-II and the RAD TX-8 as well.

The RAD sounded really great. The Sennheiser was certainly acceptable to me as well.

In our usage, we're constrained by the ambient noise of the combiners as we often are set up in very close proximity to the guests. The Shure was wonderfully quiet. Both the Sennheiser & the RAD had multiple fans for cooling. As a result, there is a certain amount of ambient noise with both units. The Sennheiser fans also exhibited (to me) a pitched component to the fan noise which wouldn't work for me.

I loved the RAD unit, but had to go with the almost silent Shure unit. The people at RAD were wonderful to work with. My newer contact at Full Compass (for the Sennheiser) not so much...

Best regards,
Bob

Title: Re: Combiner quality
Post by: Scott Helmke on March 14, 2018, 09:56:40 am
Shure has had some reliability issues with the PA821A, but now they're putting out the PA821B which addresses that issue and a couple others.
Title: Re: Combiner quality
Post by: Bob Charest on March 14, 2018, 01:32:00 pm
Shure has had some reliability issues with the PA821A, but now they're putting out the PA821B which addresses that issue and a couple others.
Hi Scott,

Iím most interested in the PA821A issues you mention, but didnít find anything when searching the web - Could you please post a bit more info? That would be really helpful to me.

Best regards,
Bob


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Title: Re: Combiner quality
Post by: Scott Helmke on March 14, 2018, 03:20:45 pm
Iím most interested in the PA821A issues you mention, but didnít find anything when searching the web - Could you please post a bit more info? That would be really helpful to me.

Not sure I could find it at this point, but I think there was a bulletin from Shure about it. We've definitely seen more failures* on the PA821A units than is typical for Shure hardware, and one of the advertised features of the PA821B is better cooling.

*individual input ports going bad
Title: Re: Combiner quality
Post by: Andrew Broughton on March 14, 2018, 07:42:25 pm
Not sure I could find it at this point, but I think there was a bulletin from Shure about it. We've definitely seen more failures* on the PA821A units than is typical for Shure hardware, and one of the advertised features of the PA821B is better cooling.

*individual input ports going bad
You mean like this?
http://forums.prosoundweb.com/index.php/topic,166442.msg1534971.html#msg1534971
Title: Re: Combiner quality
Post by: Scott Helmke on March 14, 2018, 08:25:22 pm
You mean like this?
http://forums.prosoundweb.com/index.php/topic,166442.msg1534971.html#msg1534971

Yes, though what I've always seen is just weak or no signal from the bad inputs.
Title: Re: Combiner quality
Post by: Bob Charest on March 14, 2018, 09:18:11 pm
Not sure I could find it at this point, but I think there was a bulletin from Shure about it. We've definitely seen more failures* on the PA821A units than is typical for Shure hardware, and one of the advertised features of the PA821B is better cooling.

*individual input ports going bad
Thanks, Scott.


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Title: Re: Combiner quality
Post by: Bob Charest on March 14, 2018, 09:20:02 pm
You mean like this?
http://forums.prosoundweb.com/index.php/topic,166442.msg1534971.html#msg1534971
Thanks, Andrew. I thought Iíd seen something, but my search didnít turn it up, so thatís  a big help.



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Title: Re: Combiner quality
Post by: Nathan.McBee on March 28, 2018, 09:06:34 pm
Hey all, first post here!

going back to the combiners...

Are there noticeable differences?
Do specific combiners work better with units of the same manufacturer?
what kind of specs can we use to measure these types of properties?

thanks!

-Nathan
Title: Re: Combiner quality
Post by: Scott Holtzman on March 28, 2018, 09:11:49 pm
Hey all, first post here!

going back to the combiners...

Are there noticeable differences?
Do specific combiners work better with units of the same manufacturer?
what kind of specs can we use to measure these types of properties?

thanks!



-Nathan

RF doesn't know who manufactured it.

The onus is on you to choose the right 3rd party combiner.   Power, Q, circulators, lots of chances to make a mistake. 

To me doesn't seem worth the savings.


Title: Re: Combiner quality
Post by: Brian Hancock on March 28, 2018, 09:16:44 pm
Hey all, first post here!

going back to the combiners...

Are there noticeable differences?
Do specific combiners work better with units of the same manufacturer?
what kind of specs can we use to measure these types of properties?

thanks!

-Nathan

Nathan, I think most would agree with wireless you get what you pay for ... all the listed models are quality units and work very well, however there are some subtle differences ... for example some have internal amplifiers that make up for the loss of the combiner and that power is selectable, or they have a external input to combine multiple combiners

but in all but the absolutely most demanding environments all will work very well.
Title: Re: Combiner quality
Post by: Scott Holtzman on March 28, 2018, 09:19:15 pm
[8quote author=Nathan.McBee link=topic=166778.msg1539527#msg1539527 date=1522285594]


-Nathan


Nathan, I think most would agree with wireless you get what you pay for ... all the listed models are quality units and work very well, however there are some subtle differences ... for example some have internal amplifiers that make up for the loss of the combiner and that power is selectable, or they have a external input to combine multiple combiners

but in all but the absolutely most demanding environments all will work very well.

I have never seen a combiner with an amplifier.   You might be thinking about an RX Multicoupler

Title: Re: Combiner quality
Post by: Nathan.McBee on March 28, 2018, 09:37:23 pm
well, lets take for instance the GX-8.
It seems to have an input sensitivity that favors a certain mW input.
Or the Shure PA821 is said to have a fair bit of gain loss when you use the expansion port and another combiner.

I'm wondering if others have experiences or opinions regarding these sorts of things.
If there are noticeable differences of linearity, etc.
Title: Re: Combiner quality
Post by: Scott Holtzman on March 28, 2018, 09:39:38 pm
well, lets take for instance the GX-8.
It seems to have an input sensitivity that favors a certain mW input.
Or the Shure PA821 is said to have a fair bit of gain loss when you use the expansion port and another combiner.

I'm wondering if others have experiences or opinions regarding these sorts of things.
If there are noticeable differences of linearity, etc.

It's actually an amp on every input.  From the vendors site "Each input contains its own discreet RF amplifier and proprietary ALC circuits."

Now if they can just spell discrete.
Title: Re: Combiner quality
Post by: Henry Cohen on March 29, 2018, 07:27:29 pm
well, lets take for instance the GX-8.
It seems to have an input sensitivity that favors a certain mW input.
Or the Shure PA821 is said to have a fair bit of gain loss when you use the expansion port and another combiner.

I'm wondering if others have experiences or opinions regarding these sorts of things.
If there are noticeable differences of linearity, etc.

First, as Scott noted, active combiners have amplifiers on each input that raise the carrier power to a level to compensate for subsequent combiner and insertion losses (~7dB for 4-way, ~10dB for 8-way) in unity gain units (Shure, Sennheiser, RF Venue, AT, etc). For those combiners that offer variable output levels, the amplifier stage provides additional gain beyond the combiner/insertion losses with, generally, a switchable attenuator on the output (GX-4 & GX-8), or by attenuating at the input to the amplifier (RAD TX-8).

Amplifier gain, noise figure, 1dB compression point ("P1"), third order intercept point ("IP3"), linearity and cooling are the real drivers behind the quality and cost of the combiner, along with packaging and any additional features. Digital transmission schemes and RAD's double sideband AM transmission are the most taxing on amplifier stages; amplifiers in combiners for these transmission schemes require high linearity and a very good IP3.

The expansion port on the Shure PA8/421 combiners is simply a high power passive 2-way splitter/combiner with about 3.5dB total loss.
Title: Re: Combiner quality
Post by: Brian Hancock on April 02, 2018, 09:27:10 am



The expansion port on the Shure PA8/421 combiners is simply a high power passive 2-way splitter/combiner with about 3.5dB total loss.

Henry correct me if I'm wrong but are isn't the shure combiner essentially just a mini circuits zapd-2-1 (think I got that product id close)

basically a 2 to 1 combiner splitter ?!?

Title: Re: Combiner quality
Post by: Henry Cohen on April 03, 2018, 01:29:58 pm
Henry correct me if I'm wrong but are isn't the shure combiner essentially just a mini circuits zapd-2-1 (think I got that product id close)

basically a 2 to 1 combiner splitter ?!?

Actually, more like the ZAPD-900-5W-N+ (https://www.minicircuits.com/WebStore/dashboard.html?model=ZAPD-900-5W-N%2B). Yes, it's a standard Wilkinson circuit.
Title: Re: Combiner quality
Post by: Andrew Broughton on April 15, 2018, 07:06:02 pm
The RF Venue combiner seems relatively inexpensive compared to the others. Anyone know what's different about it?
Title: Re: Combiner quality
Post by: Nathan Riddle on April 15, 2018, 08:31:09 pm
The RF Venue combiner seems relatively inexpensive compared to the others. Anyone know what's different about it?

Chris of RF Venue via email (I was asking questions) said their inputs are 100mw capable.

And that's all that I can contribute to this convo  :D
Title: Re: Combiner quality
Post by: Andrew Broughton on April 16, 2018, 03:21:04 am
Chris of RF Venue via email (I was asking questions) said their inputs are 100mw capable.
Not really sure what that means.
Title: Re: Combiner quality
Post by: Nathan Riddle on April 16, 2018, 08:18:04 am
Not really sure what that means.

It's not a listed spec on their spec sheet, so I figure when comparing the units with spec sheets that is a worthy addition.
Title: Re: Combiner quality
Post by: Andrew Broughton on April 16, 2018, 02:47:48 pm
It's not a listed spec on their spec sheet, so I figure when comparing the units with spec sheets that is a worthy addition.
Gotcha, thanks!
Title: Re: Combiner quality
Post by: Don Boomer on April 16, 2018, 08:52:13 pm
It's not a listed spec on their spec sheet, so I figure when comparing the units with spec sheets that is a worthy addition.

Check again, itís on the spec sheet😁
Title: Re: Combiner quality
Post by: Andrew Broughton on April 17, 2018, 03:00:21 pm
Other than the RF venue being 4ch and the others 8ch, it's MUCH less expensive (like 1/8th the price). I would love to know what specifically is different. No doubt an 8ch unit is more difficult to build than 4ch, but still?
Title: Re: Combiner quality
Post by: Nathan Riddle on April 17, 2018, 03:17:54 pm
Check again, itís on the spec sheet😁

Apologies  :-[ I could have sworn it wasn't  :o I should have double checked my memory with facts ;)
Title: Re: Combiner quality
Post by: frank kayser on April 18, 2018, 12:36:22 pm
So all this discussion begs the question:
What specifically is (are) the problem(s) using a generic splitter/combiner if it covers the frequency range (350-1000mhz) and as a combiner, can handle the power input from the transmitters.
For example:
https://www.instockwireless.com/rf_power_divider_combiner_splitter/pd2581-datasheet.pdf


Other non-pro sound sites claim anything covering the TV range work - reliably enough for "A" level? No.  OK for bargain basement lounge use?  I know: risk vs reward.  Buy once, cry once.


frank
Title: Re: Combiner quality
Post by: Scott Holtzman on April 18, 2018, 01:44:20 pm
So all this discussion begs the question:
What specifically is (are) the problem(s) using a generic splitter/combiner if it covers the frequency range (350-1000mhz) and as a combiner, can handle the power input from the transmitters.
For example:
https://www.instockwireless.com/rf_power_divider_combiner_splitter/pd2581-datasheet.pdf


Other non-pro sound sites claim anything covering the TV range work - reliably enough for "A" level? No.  OK for bargain basement lounge use?  I know: risk vs reward.  Buy once, cry once.


frank

The wide bandwidth does not provide for filtration.  You could add bandpass filters on the outputs but that would increase the cost.  The problem is that is after the internal amplifier.  You could also build a custom network of preselectors with the same caveat.

Lack of filtration on a wideband amplifier is just asking for intermod products. 

Title: Re: Combiner quality
Post by: Jason Glass on April 18, 2018, 01:52:10 pm
The wide bandwidth does not provide for filtration.  You could add bandpass filters on the outputs but that would increase the cost.  The problem is that is after the internal amplifier.  You could also build a custom network of preselectors with the same caveat.

Lack of filtration on a wideband amplifier is just asking for intermod products.
They also lack sufficient isolation between ports. Good wide band passives typically spec around 25dB.

Sent from my Nexus 5 using Tapatalk

Title: Re: Combiner quality
Post by: Andrew Broughton on April 18, 2018, 02:21:07 pm
Again, I still don't understand how the 8ch devices are over $5k each and the 4-channel devices that are sub-$1k? The Sennheiser AC-3 and RF Venue Combine-4 are 6-8 times cheaper.
What are the "real-world" differences that justify the huge increase in cost?
If you're only using 4 channels, do they perform the same? If you use 2 of the 4-channel units for 8 channels with antennas spaced apart, does that work as well as a single 8ch?
Title: Re: Combiner quality
Post by: Jason Glass on April 18, 2018, 02:41:06 pm
Again, I still don't understand how the 8ch devices are over $5k each and the 4-channel devices that are sub-$1k? The Sennheiser AC-3 and RF Venue Combine-4 are 6-8 times cheaper.
What are the "real-world" differences that justify the huge increase in cost?
If you're only using 4 channels, do they perform the same? If you use 2 of the 4-channel units for 8 channels with antennas spaced apart, does that work as well as a single 8ch?
The AC-3 can only handle 50mW input and the RF Venue handles 100mW. The PA821A, AC3200, and TX-8 can handle 250mW. Higher headroom, lower noise (IMD), and higher isolation are more expensive per channel because they require more components per channel and higher tolerance and performance spec'd components per channel. Then multiply by 2 to go from 4 to 8 channels and account for higher gain amps on each channel to overcome 3dB more splitter loss.

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Title: Re: Combiner quality
Post by: frank kayser on April 18, 2018, 03:12:08 pm
So, there has to be something other than a $5k solution


The Shure manual



https://522bb370f5443d4fe5b9-f62de27af599bb6703e11b472beadbcc.ssl.cf2.rackcdn.com/publication/upload/981/us_pro_antenna_setup_ea.pdf


on page 12, diagrams an 8 channel setup with 2 active splitters, then combined with passive splitters into a single set of antennae.


So, in theory, this setup would be less than half of the $5K 8-into-1 single active combiner.


Of course, something will be lost. Yes, 3dB loss in the passive splitters.   
Shure seems to think it is OK.


What problems does this configuration create?  What is missing?


frank







Title: Re: Combiner quality
Post by: Andrew Broughton on April 18, 2018, 04:42:35 pm
Thank you, Jason.

The AC-3 can only handle 50mW input and the RF Venue handles 100mW. The PA821A, AC3200, and TX-8 can handle 250mW.
I can imagine there are situations where that matters, but if I'm using it for IEMs, I'm not going to be sending it more than 50mW. The TX-8 can amplify the output anyway, so why would you need to hit it with a higher signal?

Quote
Higher headroom, lower noise (IMD), and higher isolation are more expensive per channel because they require more components per channel and higher tolerance and performance spec'd components per channel. Then multiply by 2 to go from 4 to 8 channels and account for higher gain amps on each channel to overcome 3dB more splitter loss.

Is there a way to quantify these differences?
Title: Re: Combiner quality
Post by: Lyle Williams on April 18, 2018, 05:14:00 pm
Solid state transmitters will retransmit received signals as intermodulation products at about 16dB down from the received signal.

So port isolation is critical to reducing intermod problems.  Doing the maths to work out the level of intermod products isn't hard.  Working out the impact in the real world on paper can be hard.

Better is better, but when is sufficient suffiicient?
Title: Re: Combiner quality
Post by: Ike Zimbel on April 18, 2018, 05:38:59 pm


Better is better, but when is sufficient suffiicient?
When it works for your situation. On the gigs that I'm usually doing, the game is all about minimizing un-wanted artifacts (in this case intermod products, ie: unwanted occupied frequencies) because they will start to build up. Go with something that is "good enough" here and something that "oughta' do" there and before long you have created a hostile RF environment. Especially lately, when packing a lot of channels into less bandwidth has become the order of the day. Bottom line, if you have a handful of in-ears and they work for you every night with one of the less expensive combiners, go for it.
Title: Re: Combiner quality
Post by: Andrew Broughton on April 18, 2018, 05:51:02 pm
Working out the impact in the real world on paper can be hard.

Better is better, but when is sufficient suffiicient?
When it works for your situation. On the gigs that I'm usually doing, the game is all about minimizing un-wanted artifacts (in this case intermod products, ie: unwanted occupied frequencies) because they will start to build up. Go with something that is "good enough" here and something that "oughta' do" there and before long you have created a hostile RF environment. Especially lately, when packing a lot of channels into less bandwidth has become the order of the day. Bottom line, if you have a handful of in-ears and they work for you every night with one of the less expensive combiners, go for it.

Still hoping to eventually get some quantitative information. I've no doubt that the more expensive devices are "better", but how much better exactly?
Will the more expensive product make a difference in my environment? How will I know before I buy? Where does one find non-anecdotal evidence and information that shows the real world benefit of the additional quality components?

This currently feels like the kind of discussions that happen on audiophile forums. "It's better because it's more expensive". "Ok. Prove it."
Title: Re: Combiner quality
Post by: Scott Holtzman on April 18, 2018, 08:20:48 pm
Still hoping to eventually get some quantitative information. I've no doubt that the more expensive devices are "better", but how much better exactly?
Will the more expensive product make a difference in my environment? How will I know before I buy? Where does one find non-anecdotal evidence and information that shows the real world benefit of the additional quality components?

This currently feels like the kind of discussions that happen on audiophile forums. "It's better because it's more expensive". "Ok. Prove it."

If that 6db you need to maintain your BER is lost due to a IM product then the answer is far more than semantics.  You chip away at your S/N ratio with every signal that gets into the front end of the distribution amp and comes out the other end with amplified harmonics.

Title: Re: Combiner quality
Post by: Andrew Broughton on April 18, 2018, 10:35:32 pm
If that 6db you need to maintain your BER is lost due to a IM product then the answer is far more than semantics.  You chip away at your S/N ratio with every signal that gets into the front end of the distribution amp and comes out the other end with amplified harmonics.
I get that, but are there actual numbers? I suspect nobody has done any head to heads between these devices in a controlled setting so itís very difficult to quantify the real world differences I expect.
Wish I had the time and RF chops to do it!


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Title: Re: Combiner quality
Post by: Lyle Williams on April 19, 2018, 08:02:03 am

The level of the intermod products depends on the port isolation and the number and power of input signals.

The frequency location of the intermod products depends on the choices you have made for transmitter frequencies, as well as the frequencies of other transmitters in the area.

The succeptablity of your receivers to interference depends on the quality and qualities of the receivers.

As just about everything can vary, results can vary.  If you have a situation where intermod is starting to be a problem, then a combiner with better port isolation will probably fix it.

It is easy to heckle and say it sounds like audiophile garbage.  Some reading on the basics of RF technology may help.

Title: Re: Combiner quality
Post by: Jason Glass on April 19, 2018, 03:30:37 pm
I get that, but are there actual numbers? I suspect nobody has done any head to heads between these devices in a controlled setting so itís very difficult to quantify the real world differences I expect.
Wish I had the time and RF chops to do it!


Sent from my iPhone using Tapatalk Pro
Title: Re: Combiner quality
Post by: Jason Glass on April 19, 2018, 03:31:21 pm
I get that, but are there actual numbers? I suspect nobody has done any head to heads between these devices in a controlled setting so itís very difficult to quantify the real world differences I expect.
Wish I had the time and RF chops to do it!


Sent from my iPhone using Tapatalk Pro
Title: Re: Combiner quality
Post by: Jason Glass on April 19, 2018, 03:32:07 pm
I get that, but are there actual numbers? I suspect nobody has done any head to heads between these devices in a controlled setting so itís very difficult to quantify the real world differences I expect.
Wish I had the time and RF chops to do it!


Sent from my iPhone using Tapatalk Pro
Title: Re: Combiner quality
Post by: Jason Glass on April 19, 2018, 03:33:02 pm
I get that, but are there actual numbers? I suspect nobody has done any head to heads between these devices in a controlled setting so itís very difficult to quantify the real world differences I expect.
Wish I had the time and RF chops to do it!


Sent from my iPhone using Tapatalk Pro

This TX-8 was a prototype.  Production units are much quieter.
Title: Re: Combiner quality
Post by: Jason Glass on April 19, 2018, 03:33:47 pm
I get that, but are there actual numbers? I suspect nobody has done any head to heads between these devices in a controlled setting so itís very difficult to quantify the real world differences I expect.
Wish I had the time and RF chops to do it!


Sent from my iPhone using Tapatalk Pro
Title: Re: Combiner quality
Post by: Andrew Broughton on April 19, 2018, 06:39:37 pm
Thank you so much, Jason!

I can't be reading these right, as it seems like the AC-3 has the best trace with the lowest IM!
Title: Re: Combiner quality
Post by: Mac Kerr on April 19, 2018, 07:19:51 pm
Thank you so much, Jason!

I can't be reading these right, as it seems like the AC-3 has the best trace with the lowest IM!

The AC-3 seems to have the lowest noise floor, but it also has the lowest output level. All the other units appear to be about 10dB hotter on the output. They all look pretty good as far as IM products. The prototype TX8 and older GX8 both seem to suffer from noise or low level IM products, but they are both capable of a lot of gain.

Mac
Title: Re: Combiner quality
Post by: Scott Holtzman on April 19, 2018, 07:33:48 pm
Thank you so much, Jason!

I can't be reading these right, as it seems like the AC-3 has the best trace with the lowest IM!

I count 14 birdies above the reference line on the AC-3

One thing to add that hasn't been brought up.  A combiner should also have a circulator on the output (think of it as an RF diode).  Backfeeding down the output contributes to more IM products.

A general comment about the 100mw power level.  You can make a lot of heat with 100mw.  Back in the day before digital cellular one of the largest design challenges was the duplexor (combines the RX and TX into a single antenna) even with the almost 50Mhz of spread the filter still had some loss which is dissipated as heat.  Carrying that heat away from a PC board mounted stripline type device was a bitch.  Most people thought the final amplifier was generating the heat but the hottest device in the radio was the combiner and circulator.

Title: Re: Combiner quality
Post by: Andrew Broughton on April 19, 2018, 07:53:56 pm
The AC-3 seems to have the lowest noise floor, but it also has the lowest output level. All the other units appear to be about 10dB hotter on the output. They all look pretty good as far as IM products. The prototype TX8 and older GX8 both seem to suffer from noise or low level IM products, but they are both capable of a lot of gain.

Mac
I wonder if the AC3 and Combine-4 would have the same performance?

I'm still having trouble deciding if the MUCH higher price of the 8ch combiners is justified in my case. I understand that if you need it you need it, regardless of cost. I'm just not sure if I need it! My biggest headache these days is LED video walls. I'm not sure if a combiner can help me with that!
Title: Re: Combiner quality
Post by: Jason Glass on April 20, 2018, 05:51:33 pm
I wonder if the AC3 and Combine-4 would have the same performance?

I'm still having trouble deciding if the MUCH higher price of the 8ch combiners is justified in my case. I understand that if you need it you need it, regardless of cost. I'm just not sure if I need it! My biggest headache these days is LED video walls. I'm not sure if a combiner can help me with that!
Hi Andrew,

Your observation is accurate; the AC-3 is very quiet when combining 30mW signals, below its spec'd limit. The others are transmitting 100mW.  I also failed to note that the others are combining 8 channels, which aren't visible because they're outside of the SA span shown.

When your trouble is because of wideband interference sources local to RX, such as video walls stomping IEM packs, you have roughly seven choices:
1. Attenuate RX antenna input.
2. Increase TX power.
3. Identify specific freqs where noise generated by local sources is lowest at the RX antennas and tune your IEMs to those.
4. Insert external narrow bandpass filters on RX.
5. All or most of the above.
6. Identify and shield specific components that are radiating interfering noise.
7. Change IEM systems' tuning bandwidth to one outside of local interference noise band.

FWIW, 4 is damned near impossible for IEM within practical physical size, performance specs, and budget limits. 6 is also difficult because linked LED arrays often act as a single, large area source of low level RF energy. 2 is where the best combiner that you can afford is critical, because it makes both 2 and 3 possible without generating excessive IMD on freqs that you're stuck with, regardless of IMD prediction math.

Sent from my Nexus 5 using Tapatalk

Title: Re: Combiner quality
Post by: Andrew Broughton on April 20, 2018, 07:13:55 pm
Hi Andrew,

Your observation is accurate; the AC-3 is very quiet when combining 30mW signals, below its spec'd limit. The others are transmitting 100mW.  I also failed to note that the others are combining 8 channels, which aren't visible because they're outside of the SA span shown.

When your trouble is because of wideband interference sources local to RX, such as video walls stomping IEM packs, you have roughly seven choices:
1. Attenuate RX antenna input.
2. Increase TX power.
3. Identify specific freqs where noise generated by local sources is lowest at the RX antennas and tune your IEMs to those.
4. Insert external narrow bandpass filters on RX.
5. All or most of the above.
6. Identify and shield specific components that are radiating interfering noise.
7. Change IEM systems' tuning bandwidth to one outside of local interference noise band.

FWIW, 4 is damned near impossible for IEM within practical physical size, performance specs, and budget limits. 6 is also difficult because linked LED arrays often act as a single, large area source of low level RF energy. 2 is where the best combiner that you can afford is critical, because it makes both 2 and 3 possible without generating excessive IMD on freqs that you're stuck with, regardless of IMD prediction math.

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Thank you once again, Jason. James also recommended using the RF pads on the PSM1000. (https://www.rfvenue.com/blog/2015/08/25/four-proven-strategies-for-fighting-video-wall-rf-interference (https://www.rfvenue.com/blog/2015/08/25/four-proven-strategies-for-fighting-video-wall-rf-interference))

As if it wasn't bad enough with all the frequency ranges being gobbled up by Telcoms, now we have Video Walls to deal with. RF world sure isn't getting any better.
Title: Re: Combiner quality
Post by: Jason Glass on April 20, 2018, 07:50:00 pm
Thank you once again, Jason. James also recommended using the RF pads on the PSM1000. (https://www.rfvenue.com/blog/2015/08/25/four-proven-strategies-for-fighting-video-wall-rf-interference (https://www.rfvenue.com/blog/2015/08/25/four-proven-strategies-for-fighting-video-wall-rf-interference))

As if it wasn't bad enough with all the frequency ranges being gobbled up by Telcoms, now we have Video Walls to deal with. RF world sure isn't getting any better.
Indeed. And when the video wall is actually a video floor, IEMs are not happy. There's only so much physics magic that an RF wizard can summon...

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Title: Re: Combiner quality
Post by: Henry Cohen on April 20, 2018, 08:39:07 pm
This TX-8 was a prototype.  Production units are much quieter.

[RAD hat on]
The newest hardware version, the TX-8U has significantly improved IM supression and IP3 at all output power settings, though optimal input power remains at the 50-70 mW range.
[RAD hat off] 
Title: Re: Combiner quality
Post by: Lyle Williams on April 21, 2018, 08:45:41 am
Ok, I'm going to say something that might be impractical in the real world.

It's always hard to mess about in someone else's space.

RF interference should be resolved at the source.  Maybe not this show, or the next, but the video wall supplier needs to be shown spectrum analyser images of the interference they are creating, and told to control their emissions.  That may be better grounding, or ferrites on leads, or buying a better system next time.
Title: Re: Combiner quality
Post by: Andrew Broughton on April 21, 2018, 11:04:49 pm
Ok, I'm going to say something that might be impractical in the real world.

It's always hard to mess about in someone else's space.

RF interference should be resolved at the source.  Maybe not this show, or the next, but the video wall supplier needs to be shown spectrum analyser images of the interference they are creating, and told to control their emissions.  That may be better grounding, or ferrites on leads, or buying a better system next time.
What equipment is required to pinpoint the exact source of the interference in an LED wall? I expect a spectrum analyzer and a highly directional antenna?
Are there highly directional antennas available that would work with the rf explorer?


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Title: Re: Combiner quality
Post by: Jason Glass on April 22, 2018, 12:46:27 am
What equipment is required to pinpoint the exact source of the interference in an LED wall? I expect a spectrum analyzer and a highly directional antenna?
Are there highly directional antennas available that would work with the rf explorer?


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I mounted one of these on a handle and usually insert attenuation for radiolocation with a spectrum analyzer:

http://www.wa5vjb.com/products1.html

Any passive LPDA Such as the Shure PA805, Sennheiser A2003UHF, or Audio-Technica ATW-A49 would work just as well.

Often, walking around with a PSM1000 pack with its standard whip antenna and listening for telltale whistling works better than a spectrum analyzer for location. Many sources have such wide bandwidth that it's not easy to see their signals on a spectrum trace.

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Title: Re: Combiner quality
Post by: Henry Cohen on April 22, 2018, 06:16:40 pm
What equipment is required to pinpoint the exact source of the interference in an LED wall? I expect a spectrum analyzer and a highly directional antenna? Are there highly directional antennas available that would work with the rf explorer?

Don't need a directional antenna; just a standard omni is fine. The idea is take RF noise floor measurements (in the frequency band of interest) at various distances from the wall relative to the screen powered off. When the wall is turned on, try to take the measurements when the wall has full motion video playing back, or is in full white.

Jason's practice of simply taking the IEM receiver and using it as a gauge as to how close you can get to the wall is also completely valid.
Title: Re: Combiner quality
Post by: Henry Cohen on April 22, 2018, 06:25:47 pm
Ok, I'm going to say something that might be impractical in the real world.

It's always hard to mess about in someone else's space.

RF interference should be resolved at the source.  Maybe not this show, or the next, but the video wall supplier needs to be shown spectrum analyser images of the interference they are creating, and told to control their emissions.  That may be better grounding, or ferrites on leads, or buying a better system next time.

No longer impractical. If the video wall is going to spew RF energy into the spectrum required for production wireless, that must be brought to the attention of the TD or PM. It would be the same as someone keeping bright work lights turned on which affect the lighting design of the show; would anyone expect the the LD to "stop complaining and simply make it work"?

I've had this conversation with numerous TD's and PM's, as well as video wall providers, and whereas it has taken a number of years, most folk now understand the issues and will take steps to provide a quiet wall. Though a good deal of that acquiescence is now easier due to the reputable manufacturers actually producing quite wall systems. (But these of course tend to be the more expensive walls, just like RF quiet LED bulbs.)
Title: Re: Combiner quality
Post by: Pete Erskine on April 22, 2018, 07:05:55 pm
Don't need a directional antenna; just a standard omni is fine. The idea is take RF noise floor measurements (in the frequency band of interest) at various distances from the wall relative to the screen powered off. When the wall is turned on, try to take the measurements when the wall has full motion video playing back, or is in full white.

Jason's practice of simply taking the IEM receiver and using it as a gauge as to how close you can get to the wall is also completely valid.

Last year I was hired to do RF for a musical tour at Clair.  I accepted as long as I could approve any LED walls used in the show and the producer said, that is why they wanted me!

Here are the scans I did for the vertical wall with a TTI and an omni whip.  the vendor set up a 10' by 10' wall with full brightness video program source.

First is with the wall off.
Second is with the antenna against the front of the LED  (VHF most affected)
Third is with the antenna 20' away from the center of the front
and the last is with the antenna close about 1' from the rear of the wall

The led floor vendor had roughly the same scans, also for a 10' x 10' floor.

I approved the vendors and the tour was very successful rf wise.  I was not on tour with them tho for other reasons.

Title: Re: Combiner quality
Post by: Andrew Broughton on April 23, 2018, 12:14:06 pm
Don't need a directional antenna; just a standard omni is fine. The idea is take RF noise floor measurements (in the frequency band of interest) at various distances from the wall relative to the screen powered off. When the wall is turned on, try to take the measurements when the wall has full motion video playing back, or is in full white.

Jason's practice of simply taking the IEM receiver and using it as a gauge as to how close you can get to the wall is also completely valid.
I want to pinpoint if the interference is being generated by the control circuitry, power supplies or the leds themselves, in case some shielding could be added or circuits changed. Thatís why Iím interested in pinpointing exactly where the source of interference is coming from.


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Title: Re: Combiner quality
Post by: Jason Glass on April 23, 2018, 01:05:46 pm
I want to pinpoint if the interference is being generated by the control circuitry, power supplies or the leds themselves, in case some shielding could be added or circuits changed. Thatís why Iím interested in pinpointing exactly where the source of interference is coming from.


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That's wise. A certain late night TV show that I often work uses PRG LED backlighting and set illumination. The lighting instruments are RF quiet, but occasionally one or more of their controllers cause audible squealing in IEMs. Their emissions are so low and broadband that they're invisible on an SA, but fairly easy to locate with the listening method. FWIW, you need to get extremely close before you perceive the squeal getting louder.  Enclosing the controllers in black wrap solves the problem.

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Title: Re: Combiner quality
Post by: Andrew Broughton on April 23, 2018, 01:45:06 pm
So with the "listening for squeals" method, where do you set the frequency on the receiver? Are you running it with the transmitter off? squelch off?
Title: Re: Combiner quality
Post by: Jason Glass on April 23, 2018, 02:22:14 pm
So with the "listening for squeals" method, where do you set the frequency on the receiver? Are you running it with the transmitter off? squelch off?
I start by coordinating freqs, avoiding all signals shown on the SA and calculated IMD products, as usual. Then walk test all systems with TX on, squelch @ Pilot Only (my default setting for Shure), and audio source muted. If any squeals can't be resolved by changing freq, re-scanning with the SA, etc., I start hunting for a local source with an affected RX. If I can't locate it, I start fiddling with TX antenna placement, RX attenuation, etc.  All while keeping in mind good audio gain structure into the TX when you unmute the mix, since hitting it a little harder can help to mitigate low level artifacts at the expense of dynamic range. Even open audience mics can effectively mask noise quite a bit.

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Title: Re: Combiner quality
Post by: Lyle Williams on April 23, 2018, 05:20:48 pm
I want to pinpoint if the interference is being generated by the control circuitry, power supplies or the leds themselves, in case some shielding could be added or circuits changed. Thatís why Iím interested in pinpointing exactly where the source of interference is coming from.


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It is worth noting that while many things can generate interference, things that handle more power can generate more interference.  The frequency of the interference can also provide hints.  Generally something in the interference source will be switching at a fraction of that frequency.

Possibly the most helpful advice is to note that components generally can't radiate interference.  They need to be connected to wires or circuit tracks long enough to act as effective antennas.
Title: Re: Combiner quality
Post by: Jason Glass on April 23, 2018, 07:32:31 pm
Possibly the most helpful advice is to note that components generally can't radiate interference.  They need to be connected to wires or circuit tracks long enough to act as effective antennas.

While this is valid conventional wisdom, it has not been the case on multiple gigs with PRG LED controllers. Literally wrapping only the controller enclosure with black wrap changed the situation from unusable across a 60 ft. stage to "This is great!" within 5 ft. of the controller.

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Title: Re: Combiner quality
Post by: Mac Kerr on April 23, 2018, 07:55:20 pm
While this is valid conventional wisdom, it has not been the case on multiple gigs with PRG LED controllers. Literally wrapping only the controller enclosure with black wrap changed the situation from unusable across a 60 ft. stage to "This is great!" within 5 ft. of the controller.

Is that Ronnie looking out for you?

Mac
Title: Re: Combiner quality
Post by: Jason Glass on April 23, 2018, 08:09:32 pm
Is that Ronnie looking out for you?

Mac
Haha! In all honesty, Ronnie works with me very well. As long as I approach him with the right attitude, he easily sees the big picture and works with me to make things work. He's arguably stuck his neck out for me several times, at his own peril, to show his bosses why cooperative effort works. Stephanie has also been exceptionally understanding and helpful. I'm not blowing smoke here. There's definitely a mutual respect that tempers conflicting visions of acheiving our objectives. That's why I absolutely love the gig despite its challenges!

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Title: Re: Combiner quality
Post by: Brad Harris on April 27, 2018, 10:20:01 am
Thank you once again, Jason. James also recommended using the RF pads on the PSM1000. (https://www.rfvenue.com/blog/2015/08/25/four-proven-strategies-for-fighting-video-wall-rf-interference (https://www.rfvenue.com/blog/2015/08/25/four-proven-strategies-for-fighting-video-wall-rf-interference))


That just sounds like a painful day (carrying around 24+ small SMA attenuators)

BRad
Title: Re: Combiner quality
Post by: Andrew Broughton on April 27, 2018, 05:03:50 pm
That just sounds like a painful day (carrying around 24+ small SMA attenuators)

BRad
The PSM1000 has internal padding settable in it's menu. No idea how it works, but it's selectable from 0-30db of pad in 3db increments.
I'm not sure, but I believe that's the only IEM that has this function.
Title: Re: Combiner quality
Post by: Brad Harris on April 27, 2018, 06:49:10 pm
The PSM1000 has internal padding settable in it's menu. No idea how it works, but it's selectable from 0-30db of pad in 3db increments.
I'm not sure, but I believe that's the only IEM that has this function.

Huh, never noticed that setting before. Cool!

Brad
Title: Re: Combiner quality
Post by: Gian Luca Cavalliini on May 04, 2018, 12:50:14 pm
PSM 900 also has internal RF attenuator.
Title: Re: Combiner quality
Post by: Andrew Broughton on May 22, 2018, 12:53:01 pm
[RAD hat on]
The newest hardware version, the TX-8U has significantly improved IM supression and IP3 at all output power settings, though optimal input power remains at the 50-70 mW range.
[RAD hat off] 
My supplier is saying that they can't get a price on the TX-8U, just the TX-8 and the TX 2-4U. I also don't see the TX-8U on the website. Has it not been released yet?
Title: Re: Combiner quality
Post by: Henry Cohen on May 22, 2018, 07:51:46 pm
My supplier is saying that they can't get a price on the TX-8U[/u], just the TX-8 and the TX 2-4U. I also don't see the TX-8U on the website. Has it not been released yet?

Yes; production is backlogged for TX-8U's. We expect shipping to commence in a proper manner about August. The TX-8U is simply the latest version, and although not specifically denoted that way on the website (we'll fix that soon), it is the current and only shipping (so to speak) version. Same price as the TX-8, as listed in the current dealer price sheet.
Title: Re: Combiner quality
Post by: Andrew Broughton on May 03, 2019, 03:30:03 pm
Looks like Lectro has come out with a new combiner (https://www.lectrosonics.com/US/M2C-Active-Antenna-Combiner/product.html) to go with their Duet system.
In speaking to them, they say that this combiner is designed to work best with their Digital system, keeping intermod as low as possible when using a digital system.
I don't understand it, but supposedly the digital transmission system has different requirements to the "regular" analog transmission of other products.
Title: Re: Combiner quality
Post by: Lyle Williams on May 03, 2019, 04:56:50 pm
Analogue transmitters generate a few peaks in the spectrum, so a device for use needs to accomodate a few peaks without generating too many more.  Testing is done by having a couple of test signals and measuring the intermod peaks.

Rather than being narrow peaky signals, digital is often wide swathes of spetrum.  All signal, all the time.  Digital works fine through analogue combiners, but if you want to measure the performance at the ragged edge (and find the hottest wideband signals you can push through it) then a different test method is used.  A wideband signal occupying the full bandwidth of the device is applied, with a deep and very narrow notch filtered out.  Signal levels are increased until intermod starts to fill in the notch.
Title: Re: Combiner quality
Post by: Tim Hite on May 04, 2019, 04:03:03 am
I skimmed through the rest of this thread and didn't see this new product mentioned. Lectrosonics has them in stock right now.

https://www.lectrosonics.com/US/lectrosonics-introduces-the-m2c-active-antenna-combiner.html?fbclid=IwAR2H4m0kl8oNbzKwVH2yAThQc8wNgN8q1GjytBqpeiaTj07VyHYjzIARhRY


How do the following combiners rate in terms of signal quality?

Shure PA821A (https://www.shure.com/americas/products/accessories/personal-monitor-systems/psm-antenna-combiners/pa821a-psm-antenna-combiner)
Sennheiser AC3200-II (https://en-us.sennheiser.com/ac-3200-ii)
RF Venue Combine-4 (https://www.rfvenue.com/products/combine4)
RAD TX-8 (http://radioactiverf.com/home/products/combiners-splitters/tx-8-transmitter-combiner/)

I would assume the RAD TX-8 would be at the top of the list, but how do the Shure and Senn compare? Anyone done or seen tests on these devices? Are there any other quality products out there that I'm missing?

My application would be the using these with LectroSonics M2-Duet series IEMs but also possibly with Shure PSM1000/Sennheiser 2000 series IEMs.

Thanks!
Title: Re: Combiner quality
Post by: Andrew Broughton on May 04, 2019, 11:26:45 am
I skimmed through the rest of this thread and didn't see this new product mentioned.

Umm... Really (https://forums.prosoundweb.com/index.php/topic,166778.msg1574941.html#msg1574941)?
Title: Re: Combiner quality
Post by: Tim Hite on May 04, 2019, 04:15:37 pm
I did say skimmed. . .I may have lost focus somewhere around the 'whistling video walls' portion of this thread. . .

Umm... Really (https://forums.prosoundweb.com/index.php/topic,166778.msg1574941.html#msg1574941)?
Title: Re: Combiner quality
Post by: Steve Litscher on August 19, 2019, 01:59:49 pm
Reviving this thread with the hope of finding someone who is/has used the PSM 1000 system with the RF Venue Combine4 system.

I've got 4 channels of PSM 1000 and am about to pull the trigger on a combiner. There's good info in here, but I wasn't able to extract any real world experience/advice about the RF Venue Combine4.

Heading out on a USA tour, smaller theaters (2500-ish cap). Want to make certain I have a stable, reliable combiner and would prefer to not break the bank (if possible). Even with deep discounts, the Shure PA421B is still nearly 3x more than the RF Venue...

Thanks in advance.
Title: Re: Combiner quality
Post by: Nathan Riddle on August 19, 2019, 02:49:45 pm
Reviving this thread with the hope of finding someone who is/has used the PSM 1000 system with the RF Venue Combine4 system.

I've got 4 channels of PSM 1000 and am about to pull the trigger on a combiner. There's good info in here, but I wasn't able to extract any real world experience/advice about the RF Venue Combine4.

Heading out on a USA tour, smaller theaters (2500-ish cap). Want to make certain I have a stable, reliable combiner and would prefer to not break the bank (if possible). Even with deep discounts, the Shure PA421B is still nearly 3x more than the RF Venue...

Thanks in advance.

Mine seems to work fine. Though no matter what I do there's always some dropouts/fuzz in the IEM's it seems. My biggest improvement for that was a helical antenna (RFVenue version).
Title: Re: Combiner quality
Post by: Steve Litscher on August 19, 2019, 02:58:22 pm
Oh cool - I didn't know you had the Combine4. Good to know. And yeah, I'm definitely grabbing the CP Beam for whichever combiner I go with.

How far away is your antenna from the performers? I'll have the luxury of placing my rig side stage... I'm hoping that helps a bunch.
Title: Re: Combiner quality
Post by: John Sulek on August 19, 2019, 03:58:11 pm
Oh cool - I didn't know you had the Combine4. Good to know. And yeah, I'm definitely grabbing the CP Beam for whichever combiner I go with.

How far away is your antenna from the performers? I'll have the luxury of placing my rig side stage... I'm hoping that helps a bunch.

Height is your friend. Less salty water bags in the way.
Sometimes upstage pointing towards the downstage edge works best...all depends on the layout and what you can get away with scenic-wise.
Title: Re: Combiner quality
Post by: Tim McCulloch on August 19, 2019, 04:01:38 pm
IIRC the helical antennae have a beam spread of about 30 degrees.  An RF cannon may not be the best solution.  The domed helicals might be wider.

On most stages in a reasonable RF noise environment, better placement of Log Periodic antennae has more positive effect with fewer 'out of coverage' issues than a helical.  In high noise environments the helical may offer more advantages.

Height is your friend. Less salty water bags in the way.
Sometimes upstage pointing towards the downstage edge works best...all depends on the layout and what you can get away with scenic-wise.

^^^ THIS
Title: Re: Combiner quality
Post by: Steve Litscher on August 19, 2019, 04:28:41 pm
Thanks again guys - I'll definitely get the antenna raised as high as I can, and I'll check the coverage patterns of the CP Beam vs the domed helical.
Title: Re: Combiner quality
Post by: Jason Glass on August 19, 2019, 05:40:02 pm
IIRC the helical antennae have a beam spread of about 30 degrees.  An RF cannon may not be the best solution.

Antenna beamwidth is a largely misunderstood by too many users, IMHO.  First of all, the CP Beam beamwidth is 70į.  This means that at 35į off-axis, the directional gain is 3 dB lower than on-axis.  Since the CPB's on-axis gain is 11 dBi, you still have 8 dBi of gain at that angle.  Then it's wise to deduct 3 dB for polarization mismatch loss between the circular polarized TX and randomly oriented linear RX.  This leaves you with gain at 35į off-axis that is roughly equal to an LPDA pointed directly at that position.  From that angle outward, gain doesn't just cut off.  It gradually decreases until minimums located approximately 120į to 160į off-axis, then shoots way up inside a hot lobe between 160į and 180į.

If you overlay the polar pattern of a helical antenna such as the CP Beam or PWS HA-xxxx over a rectangular stage, you'll find that mounting it offstage of an upstage corner and pointing to the opposite diagonal downstage corner offers nearly ideal gain distribution to cover the stage.  You'll see that the highest gain on the axis points toward the most distant likely performer position while closer positions correlate with off-axis gain dropoff.
Title: Re: Combiner quality
Post by: Henry Cohen on August 19, 2019, 06:13:03 pm
Antenna beamwidth is a largely misunderstood by too many users, IMHO.  First of all, the CP Beam beamwidth is 70į.  This means that at 35į off-axis, the directional gain is 3 dB lower than on-axis.  Since the CPB's on-axis gain is 11 dBi, you still have 8 dBi of gain at that angle.  Then it's wise to deduct 3 dB for polarization mismatch loss between the circular polarized TX and randomly oriented linear RX.  This leaves you with gain at 35į off-axis that is roughly equal to an LPDA pointed directly at that position.  From that angle outward, gain doesn't just cut off.  It gradually decreases until minimums located approximately 120į to 160į off-axis, then shoots way up inside a hot lobe between 160į and 180į.

If you overlay the polar pattern of a helical antenna such as the CP Beam or PWS HA-xxxx over a rectangular stage, you'll find that mounting it offstage of an upstage corner and pointing to the opposite diagonal downstage corner offers nearly ideal gain distribution to cover the stage.  You'll see that the highest gain on the axis points toward the most distant likely performer position while closer positions correlate with off-axis gain dropoff.

THIS  ^^^^^^^^^
Title: Re: Combiner quality
Post by: Bob Charest on August 19, 2019, 08:50:58 pm
THIS  ^^^^^^^^^
Yes, for sure. The attached pic shows how we did this from the upstage corner aimed at the downstage corner opposite.
Title: Re: Combiner quality
Post by: Rick Earl on August 20, 2019, 09:49:48 am
Reviving this thread with the hope of finding someone who is/has used the PSM 1000 system with the RF Venue Combine4 system.

I've got 4 channels of PSM 1000 and am about to pull the trigger on a combiner. There's good info in here, but I wasn't able to extract any real world experience/advice about the RF Venue Combine4.

Heading out on a USA tour, smaller theaters (2500-ish cap). Want to make certain I have a stable, reliable combiner and would prefer to not break the bank (if possible). Even with deep discounts, the Shure PA421B is still nearly 3x more than the RF Venue...

Thanks in advance.

I have been using the Combine 4 with Sennheiser EW-300 and a CP-Beam for a couple of years now with no issues.   Inside, outside, close to stage and almost 80' from stage.  One group on campus uses it 3 times a week for rehearsals for 2 1/2 hours a day.   I would say it is reliable and as quiet as the EW-300's on their own. 
Title: Re: Combiner quality
Post by: Steve Litscher on August 20, 2019, 02:13:38 pm
Thanks again everyone, and Jason/Bob thanks for the extra detailed info. Much appreciated!!

I talked to Don from RF Venue yesterday and learned *a ton* from him. I pulled the trigger on a RF Venue Combine4 with CP Beam today and will get everything racked-up and ready to test within the next few weeks. I'll let you know how it goes, but based on what Don shared, I'm thinking this will be a winning combination.
Title: Re: Combiner quality
Post by: Nathan Riddle on August 20, 2019, 04:14:53 pm
Thanks again everyone, and Jason/Bob thanks for the extra detailed info. Much appreciated!!

I talked to Don from RF Venue yesterday and learned *a ton* from him. I pulled the trigger on a RF Venue Combine4 with CP Beam today and will get everything racked-up and ready to test within the next few weeks. I'll let you know how it goes, but based on what Don shared, I'm thinking this will be a winning combination.

What all did you learn?

---

To answer your earlier question. I've had a few configs.

1/2 wave antenna at foh (50ft from stage) on 2x mipro 909digital
1/4 wave antenna farm on 4x ew300's G50 band side stage
1/2 wave side stage with 100ft LMR400 (generic) & combine 4
1/2 wave side stage with 25ft RG6U (RF venue) & combine 4
Helical with 25ft RG6U (RF venue) & combine 4

Helical resulted in best RF performance the above list also coincides with performance from low to high.

It also is inversely proportional with band complaints.
Title: Re: Combiner quality
Post by: Jason Glass on August 20, 2019, 05:34:56 pm
Helical resulted in best RF performance the above list also coincides with performance from low to high.

It also is inversely proportional with band complaints.

 ;D ;D ;D ;D ;D  The most important metric known to every Monitor Engineer.   ;D ;D ;D ;D ;D
Title: Re: Combiner quality
Post by: Steve Litscher on August 20, 2019, 06:35:58 pm
What all did you learn?

---



We talked for a good 15 minutes or so, about a number of RF-related items, so it's hard to summarize it all, but the key take-aways (and, I'm *super heavily* paraphrasing here):

- RG8X cable (double-shielded) provides better protection against noise; use if you can
- Don't bundle/wrap antenna cables together in rack; leave loose
- If you can get away with it, run the PSM 1000 at lower power and let the Combiner/antenna help out with gain
- If using Shure WWB to scan frequencies, include +/- 50 MHz from target range - it'll help it make a better decision
- Really would be better to have a dedicated RF scanner, but WWB can do the trick

We talked a little about the technology differences and also talked about interference sources, common issues, etc.. Again, I'm distilling-down a bunch of info into a few bullet-points, so take it for what that's worth. Don was super helpful and I hope I'm not over-simplifying too much.
Title: Re: Combiner quality
Post by: Henry Cohen on August 20, 2019, 10:09:15 pm

We talked for a good 15 minutes or so, about a number of RF-related items, so it's hard to summarize it all, but the key take-aways (and, I'm *super heavily* paraphrasing here):

- RG8X cable (double-shielded) provides better protection against noise; use if you can

RG8X is not a specification for double shield; in fact most RG8X manufactured is a single 95% shield. To get a double shielded .24" OD (RG8X size equivalent) coax, you must look for coax that explicitly states it's double shielded (e.g. Times Microwave LMR240).

However, for transmit applications, even if only a 25' length, a double shielded .405" OD coax (LMR400, Belden 9913F7, PWS S3018 and S9046) is still a better choice due to lower losses, which are more significant as a percentage of ERP.
Title: Re: Combiner quality
Post by: Don Boomer on August 22, 2019, 11:22:10 am
Sorry ... I forget that because our RF Venue RG8x is double shielded with a braid and a foil shield that everybody doesnít do it that way. 😁
Title: Re: Combiner quality
Post by: Steve Litscher on August 22, 2019, 02:26:17 pm
Sorry ... I forget that because our RF Venue RG8x is double shielded with a braid and a foil shield that everybody doesnít do it that way. 😁

I purchased the RFV RG8x cable for my CP Beam, so whew - all good!