ProSoundWeb Community

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: Philip Roberts on February 16, 2016, 09:34:04 PM

Title: Antenna splitters
Post by: Philip Roberts on February 16, 2016, 09:34:04 PM
For building up small systems (4-8 receivers) used in relatively rural areas what down sides are there to using standard/cheap CATV splitter in place of a more expensive splitter?

Thanks

Philip
Title: Re: Antenna splitters
Post by: Pete Erskine on February 16, 2016, 11:06:38 PM
For building up small systems (4-8 receivers) used in relatively rural areas what down sides are there to using standard/cheap CATV splitter in place of a more expensive splitter?

Thanks

Philip

Shouldn't be a problem up to about 4 RX with antenna lines <50'.
Title: Re: Antenna splitters
Post by: Russell Ault on February 17, 2016, 02:18:45 AM
Shouldn't be a problem up to about 4 RX with antenna lines <50'.

Hi Pete!

Can you explain this a little further? Why only up to 4?

Thanks!

-Russ
Title: Re: Antenna splitters
Post by: Pete Erskine on February 17, 2016, 10:27:24 AM
Hi Pete!

Can you explain this a little further? Why only up to 4?

Thanks!

-Russ

Passive splitter/combiners, unless you spend $ have loss.  The more inputs you try to combine at the same time the more loss.  Including the antenna cable the loss can become great enough to make your RX or TX perform noticeably poorer as opposed to a single antenna in the device.
Title: Re: Antenna splitters
Post by: Russell Ault on February 18, 2016, 12:15:37 AM
Passive splitter/combiners, unless you spend $ have loss.  The more inputs you try to combine at the same time the more loss.  Including the antenna cable the loss can become great enough to make your RX or TX perform noticeably poorer as opposed to a single antenna in the device.

Ah, okay, I was assuming that an 8-way CATV splitter had to be active, but that's obviously not the case. That being said, what are your thoughts on using unity gain active CATV splitters for RX antenna distro?

Thanks!

-Russ
Title: Re: Antenna splitters
Post by: Pete Erskine on February 18, 2016, 10:38:26 AM
Ah, okay, I was assuming that an 8-way CATV splitter had to be active, but that's obviously not the case. That being said, what are your thoughts on using unity gain active CATV splitters for RX antenna distro?

Thanks!

-Russ

Probably not good,  try it though.
Title: Re: Antenna splitters
Post by: Russell Ault on February 20, 2016, 09:41:33 PM
Probably not good,  try it though.

I'm in the process of organizing the equipment to do just that, based off what was done here (https://www.youtube.com/watch?v=SH3VKHcwDj0) (although I'm planning to use Sennheiser antennas).

Before I spend someone else's hard-earned money on this project, though, I'm trying to think of a reason why it wouldn't work, and so far I've come up blank. The impedance mismatch issue is really a non-issue on the receive side (as discussed, I believe, elsewhere on these forums), and a unity-gain split won't over- or under-drive the receivers. If I understand this correctly, it all hangs on the quality of the amplifier in the splitter, but wouldn't something that passes analogue and DTV signals without problems also pass UHF microphone signals equally well (radio waves are just radio waves, after all...)? Am I missing anything?

Of course, what I'd really love is for someone here to show me why this won't work before I start my experiments, especially since I haven't hit the "purchase now" button yet.  :D

Thanks!

-Russ
Title: Re: Antenna splitters
Post by: Keith Broughton on February 21, 2016, 10:15:51 AM

Of course, what I'd really love is for someone here to show me why this won't work before I start my experiments, especially since I haven't hit the "purchase now" button yet.  :D

Thanks!

-Russ
You could contact the Sennheiser or Shure engineers and ask them.
I know they want to sell gear but think of this, if the CATV splitter works, why don't you see it in any wireless mic racks?
Title: Re: Antenna splitters
Post by: Henry Cohen on February 21, 2016, 11:35:53 AM
I'm in the process of organizing the equipment to do just that, based off what was done here (https://www.youtube.com/watch?v=SH3VKHcwDj0) (although I'm planning to use Sennheiser antennas).

Before I spend someone else's hard-earned money on this project, though, I'm trying to think of a reason why it wouldn't work, and so far I've come up blank. The impedance mismatch issue is really a non-issue on the receive side (as discussed, I believe, elsewhere on these forums), and a unity-gain split won't over- or under-drive the receivers. If I understand this correctly, it all hangs on the quality of the amplifier in the splitter, but wouldn't something that passes analogue and DTV signals without problems also pass UHF microphone signals equally well (radio waves are just radio waves, after all...)? Am I missing anything?

Of course, what I'd really love is for someone here to show me why this won't work before I start my experiments, especially since I haven't hit the "purchase now" button yet.  :D

As you've surmised, the primary issue will be the quality of the amplifier. What are its 1dB compression and IP3 (saturation) specifications? The amplifier needs to be able to handle the composite power levels expected. The other aspect is the port to port isolation and the actual power level balance at each output port. In other words, a cheap splitter will not provide the same quality and performance as a higher priced, better quality unit.

The fact that the splitter is 75 ohm is somewhat moot. I would only suggest that you use a coax - and proper impedance connectors - of matching impedance. 75 ohm coax of equivalent size will actually have slight less attenuation than a 50 ohm coax. And, a bit of history: Sennheiser RX splitters of 70's and 80's vintage used all 75 ohm CATV parts.
Title: Re: Antenna splitters
Post by: Lyle Williams on February 21, 2016, 02:43:42 PM
The legit splitter will be mechanically packaged in a way suitable for the market.  It will also do ancilliary functions like power distribution.

A home-grade TV splitter may be mechanically packaged cheaply.  A good CATV splitter will probably be very durably packaged, but this packaging may not be optomised for audio use.

The amp in a good CATV splitter should be of excellent quality.  It's a huge market, and RF performance matters a lot more than in our audio applications.

Title: Re: Antenna splitters
Post by: Russell Ault on February 21, 2016, 11:55:34 PM
You could contact the Sennheiser or Shure engineers and ask them.
I know they want to sell gear but think of this, if the CATV splitter works, why don't you see it in any wireless mic racks?

The way I tend to look at it (and, to be sure, this is from the bottom looking up) is that there are many factors that go into choosing the right tool for a job: cost is always a factor (although its importance starts to diminish slightly as the cost of a particular tool becomes a smaller and smaller fraction of the overall budget of the project), as is the relative importance of being able to rely on a tested, major-manufacturer product (which starts to become more important as budgets go up and having a "no one was ever fired for buying IBM"-style company attached to gear that failed may be the thing that saves your job when the lead singers mic goes dead in front of 60k people).

Most (but, admittedly, not all) of the wireless racks I've seen that use proper distro are on shows where jobs are on the line if something fails, and I'm simply not there yet. I'm still at the level where, if only one mic (out of seven) decides to randomly pop during a show, that was a good show. The group-owned RF gear I'm dealing with wasn't what I would have spec'd, and now I'm trying to make the best of a bad situation while saving as much as possible to buy decent gear down the road, so for me, the cost of the tool is far more important than it's brand-name reputation: if it works, I'll take it (something almost has to be better than nothing at this point), and if we need better down the road, it won't cost too much to replace.

As you've surmised, the primary issue will be the quality of the amplifier. What are its 1dB compression and IP3 (saturation) specifications? The amplifier needs to be able to handle the composite power levels expected. The other aspect is the port to port isolation and the actual power level balance at each output port. In other words, a cheap splitter will not provide the same quality and performance as a higher priced, better quality unit.
The amp in a good CATV splitter should be of excellent quality.  It's a huge market, and RF performance matters a lot more than in our audio applications.

The splitter I've been looking at is the PCT-VC-9U (http://pctcorporate.com/images/stories/realtimedox/datasheets/amplifiers/PCT-Bypass-Amplifiers-Uninterrupted%20Service_200909b_20110714.pdf). The only specification (of the ones Henry suggested) that I can decipher is port-to-port isolation, which is probably less than would be ideal (>22dB vs Shure's >30dB). Of course, part of the problem of knowing whether this splitter is up to the job is the lack of full specifications on Shure's and Sennheiser's products, at least that I can find, which makes comparison very difficult. Judging by the information here (which I fully expect isn't enough to make any real conclusions) is there a chance that this might work?

A home-grade TV splitter may be mechanically packaged cheaply.  A good CATV splitter will probably be very durably packaged, but this packaging may not be optomised for audio use.

I really don't know the CATV splitter market well enough to even guess what end of the spectrum this one would fall on. Obviously not rack-mountable, but a shelf will fix that, and it doesn't look like it's going to fall apart...

The fact that the splitter is 75 ohm is somewhat moot. I would only suggest that you use a coax - and proper impedance connectors - of matching impedance. 75 ohm coax of equivalent size will actually have slight less attenuation than a 50 ohm coax. And, a bit of history: Sennheiser RX splitters of 70's and 80's vintage used all 75 ohm CATV parts.

I was planning on using RG6 for that very reason. From what I've been seeing on various attenuation charts, it'll beat LMR-240 in our UHF band and is less than a quarter the price. Astonishing what volume production can do...

Thanks everyone!

-Russ
Title: Re: Antenna splitters
Post by: Lyle Williams on February 22, 2016, 12:24:57 AM
That one would seem to do.  Are you going to use two for the diversity antennas?
Title: Re: Antenna splitters
Post by: Keith Broughton on February 22, 2016, 06:20:25 AM
It looks like it's an inexpensive item so give it a try and let us know how it goes. :)
Title: Re: Antenna splitters
Post by: Russell Ault on February 22, 2016, 09:20:09 AM
That one would seem to do.  Are you going to use two for the diversity antennas?

That's the plan. And two of those is an order of magnitude cheaper than 8 channels of Sennheiser or Shure distro...

It looks like it's an inexpensive item so give it a try and let us know how it goes. :)

I'll be sure to report back with my results! :)

Thanks all!

-Russ
Title: Re: Antenna splitters
Post by: Jason Glass on February 22, 2016, 10:51:05 AM
For building up small systems (4-8 receivers) used in relatively rural areas what down sides are there to using standard/cheap CATV splitter in place of a more expensive splitter?

Thanks

Philip

There are some details about antenna splitting (and amplification, in the case of unity gain splitters) that should be mentioned in this discussion to assure that we all understand why pro audio splitters are optimal for their job, and why cheaper alternatives might work but also might not.

Efficient and effective antenna splitting is more complex than simply compensating for losses, impedance mismatch, and port isolation.

Professional audio grade splitters usually contain filtering that passes frequencies of interest while blocking undesirable out of band signals.  When these signals enter an active RF stage, the lowest noise floor and IMD products are generated when out of band signals are suppressed.

Wideband cable TV splitters include the FM radio broadcast band, which contains very strong transmission signals that can contribute to internal IMD in your receiving equipment.  This is why some cable systems insert "FM traps" into in-home cabling that includes active distribution.  These systems also allow high power two-way radio signals in the commercial 450-470MHz band to pass, along with other undesirable carriers across their entire pass band.  This is a non-issue in most residential installations, but can be a major issue in industrial applications like entertainment venues where all kinds of strong radio transmissions are in use.  It's worth noting that residential locations that have HAMs for neighbors can experience TV interference due to out of band transmissions from the local HAM shack, even in a closed circuit like cable TV.  This is a similar scenario to a 5W walkie stomping on your mics even though they are operating in different frequency bands.

As most readers here know by now, impedance mismatch causes a predictable loss of signal due to signal reflection.  This can be manageable.  However, some passive bandpass and band blocking filtering inside your receiving equipment relies on a specific range of impedance in the transmission path to determine the filter's corner frequencies, slope, band blocking depth, and pass band insertion loss.  When the impedance of the line is out of tolerance, these filter characteristics may also shift out of tolerance.  This impedance mismatch also makes it difficult to use relatively inexpensive off-the-shelf insertable filters to solve specific problems that might pop up, which pro RF techs often do.

All of this info is not intended to discourage experimentation, because it just might work fine for a given scenario and save some $.  I just want to help clarify what's going on inside those pricey black boxes.
Title: Re: Antenna splitters
Post by: Lyle Williams on February 23, 2016, 01:06:37 PM
While the pro-audio splitters probably roll off VHF, I'd be suprised if any notched out any bands within their specified frequency range.

The price of these splitters is highway robbery (for what they really contain, incl design effort)
Title: Re: Antenna splitters
Post by: John Sulek on February 23, 2016, 05:34:19 PM
While the pro-audio splitters probably roll off VHF, I'd be suprised if any notched out any bands within their specified frequency range.

The price of these splitters is highway robbery (for what they really contain, incl design effort)

No notch filters, but two of the expensive options (Axient AXT630 and Sennheiser ASA3000) can do 60Mhz bandpass filters that cover their respective transmitter frequency ranges.
Front panel switch on the Axient, swap-able hardware modules on the Sennheiser. The Axient also has an unfiltered out for cascading.
Good for noisy environments.
Title: Re: Antenna splitters
Post by: Jason Glass on February 23, 2016, 09:50:32 PM
While the pro-audio splitters probably roll off VHF, I'd be suprised if any notched out any bands within their specified frequency range.

The price of these splitters is highway robbery (for what they really contain, incl design effort)

I wasn't referring to notches within the specified band.  I was referring to stop bands and sufficient filter slopes at the edges of the pass band.  These significantly reduce the noise level in the pass band generated by subsequent active stages.  Wideband cable TV splitters and DA's typically pass <54MHz to >800MHz without any filtering at all.
Title: Re: Antenna splitters
Post by: Keith Broughton on February 24, 2016, 08:28:51 AM
Here is a question about splitters.
John Sulek and I worked with a band that has (correct me John if wrong) 12 mic receivers wired like this...
Antennas into the first active splitter that fed 3 receiver and the forth out cascaded to a second splitter...and so on.
Despite scanning a nice clean RF space, we had a hard time finding "clean" freqs for the last receivers. They were showing RF activity on pretty much all of the available channels.
Seems to me the first splitter should feed the 3 other splitters and they in turn feed 3 groups of 4 receivers.
Or, a passive 3 split feeding the 3 active splitters.
Thoughts?
Title: Re: Antenna splitters
Post by: Jason Glass on February 24, 2016, 09:25:02 AM


...the first splitter should feed the 3 other splitters and they in turn feed 3 groups of 4 receivers.
Or, a passive 3 split feeding the 3 active splitters.
Thoughts?

Yes, these are your best options.  The scenario you described was behaving exactly as one would expect with too many cascaded active components.

Jason Glass
http://cleanwirelessaudio.com

Title: Re: Antenna splitters
Post by: Keith Broughton on February 24, 2016, 09:34:46 AM

 behaving exactly as one would expect with too many cascaded active components.

Jason Glass
http://cleanwirelessaudio.com
That meaning the active stages can contribute to intermod artifacts?
So the next question is , would a passive initial split to the 3 active splitters  be better even though there is a bit of loss in signal strength?
Title: Re: Antenna splitters
Post by: Jason Glass on February 24, 2016, 09:40:09 AM
That meaning the active stages can contribute to intermod artifacts?
Yes. Not only intermodulation, but also received noise,  internally generated noise, harmonics, and spurious signals being amplified at each stage.

Jason Glass
http://cleanwirelessaudio.com

Title: Re: Antenna splitters
Post by: Jason Glass on February 24, 2016, 09:44:28 AM


would a passive initial split to the 3 active splitters  be better even though there is a bit of loss in signal strength?

I did that very thing in my Tonight Show rig. You just need to make sure that you choose an antenna with enough gain to overcome the total path loss, including splitter loss, to receive a satisfactory signal level at the receivers.

Jason Glass
http://cleanwirelessaudio.com

Title: Re: Antenna splitters
Post by: Keith Broughton on February 24, 2016, 10:14:05 AM

I did that very thing in my Tonight Show rig. You just need to make sure that you choose an antenna with enough gain to overcome the total path loss, including splitter loss, to receive a satisfactory signal level at the receivers.

Jason Glass
http://cleanwirelessaudio.com
Thanks for the info Jason :)
Title: Re: Antenna splitters
Post by: Russell Ault on February 24, 2016, 03:19:25 PM
No notch filters, but two of the expensive options (Axient AXT630 and Sennheiser ASA3000) can do 60Mhz bandpass filters that cover their respective transmitter frequency ranges.
Front panel switch on the Axient, swap-able hardware modules on the Sennheiser. The Axient also has an unfiltered out for cascading.
Good for noisy environments.

Does anyone know, offhand, what RF processing actually goes on "under the hood" in, say, the ASA 1 or the UA844SWB/UA845SWB? Presumably its something like "wide bandpass filter -> amplifier -> splitter" (with a DC injector at the end if you're Sennheiser), but the manuals for those items mention almost nothing about, for example, what filtering is actually happening (the Sennheiser-provided block diagram mentions nothing about filtering at all).

Thanks!

-Russ
Title: Re: Antenna splitters
Post by: Lyle Williams on February 25, 2016, 12:49:24 AM
I'd expect that filter/amp/split/inject sequence to be the case.  My splitter is built from minicircuits parts.  Does anyone have an ASA1 and a VNA to see what filtering occurs?
Title: Re: Antenna splitters
Post by: Russell Ault on February 25, 2016, 02:57:51 PM
I'd expect that filter/amp/split/inject sequence to be the case.  My splitter is built from minicircuits parts.  Does anyone have an ASA1 and a VNA to see what filtering occurs?

If you don't mind sharing, which Mini-Circuits parts?

Thanks!

-Russ
Title: Re: Antenna splitters
Post by: Lyle Williams on February 26, 2016, 04:58:16 AM
Passive 2-way is ZAPD-21, like http://www.akg.com/pro/p/zapd-21 but mine have SMA connectors instead of BNC.

Active 4-way is 2dB attenuator followed by BLP-750 lowpass followed by ZFL-1000 amp followed by ZFSC-4-1 splitter.

Obviously two chains of the above items for diversity RX.

When buying second hand you really just hunt around for suitable parts at suitable prices.  A lot of this used gear seems to come out of Israel, for reasons that escape me.
Title: Re: Antenna splitters
Post by: Lyle Williams on February 26, 2016, 05:03:43 AM
For some price context (in my neck of the woods, Australia) 2x ZAPD-21 (used) is $50, a ASA1 is $800.
Title: Re: Antenna splitters
Post by: Jason Glass on February 26, 2016, 11:00:09 AM
Passive 2-way is ZAPD-21, like http://www.akg.com/pro/p/zapd-21 but mine have SMA connectors instead of BNC.

Active 4-way is 2dB attenuator followed by BLP-750 lowpass followed by ZFL-1000 amp followed by ZFSC-4-1 splitter.

Obviously two chains of the above items for diversity RX.

When buying second hand you really just hunt around for suitable parts at suitable prices.  A lot of this used gear seems to come out of Israel, for reasons that escape me.

Hi Lyle,

Your Mini-Circuits DA is similar to my 4x4 multi zone DA.  Its input is a ZFSC-4-1 (surface mount on an old Vega PCB) which loops out of my chassis after combining via BNC for inserting external filters and attenuators > ZFL-1000VH > ZFSC-4-1 (duplicate of input PCB) > BNC outputs.  It works well for zoned intercom RX, and it's versatile because I can choose appropriate filters for the desired freq range before the signal path enters the amp.  I usually insert rotary stepped attenuators before the inputs to adjust each zone's overlap.

Just like yours, many of my parts are surplus eBay finds.  Having the flexibility of component parts at a fraction of the cost of dedicated assemblies can be a huge advantage.

BTW, your your DA setup is very close to what was inside 1990's Vega DA's.  Here in the States, the inserted attenuator was 6dB, and the pre filter was a 450 MHz high pass in their UHF units.  When you can find them on eBay for cheap, they are a goldmine of useful components.
Title: Re: Antenna splitters
Post by: Russell Ault on February 26, 2016, 03:15:49 PM
Active 4-way is 2dB attenuator followed by BLP-750 lowpass followed by ZFL-1000 amp followed by ZFSC-4-1 splitter.

Just curious about your filtering choice: I take it that your more worried about cell phone signals than (for example) FM radio transmissions?

Thanks!

-Russ
Title: Re: Antenna splitters
Post by: Lyle Williams on February 27, 2016, 01:58:14 AM
Yes, people with cell phones stand near the antennas, while broadcast transmitters generally keep their dustance.  I probably don't need the filter nor the attenuator, but best practice suggested it.  Had I found an appropriate bandpass filter, that would have benn an even better choice! Antennas can provide some selectivity too.

Title: Re: Antenna splitters
Post by: Diogo Nunes Pereira on May 20, 2016, 02:37:04 AM
Your Mini-Circuits DA is similar to my 4x4 multi zone DA.  Its input is a ZFSC-4-1 (surface mount on an old Vega PCB) which loops out of my chassis after combining via BNC for inserting external filters and attenuators > ZFL-1000VH > ZFSC-4-1 (duplicate of input PCB) > BNC outputs.  It works well for zoned intercom RX, and it's versatile because I can choose appropriate filters for the desired freq range before the signal path enters the amp.  I usually insert rotary stepped attenuators before the inputs to adjust each zone's overlap.

Hi Jason,

So, if I'm getting this right...

this seems to be a device with 4 inputs; four zones, and therefore four antennas. The input is a passive combiner.
Then you have a BNC connection after the combined input for filters and attenuators. How much loss do you incurr here, usually?
You then amplify this (I suppose because of split, atennuator and/or filter losses) 20dB as seen in ZFL-1000VH spec sheet. Isn't this too much?
Then you feed this signal to up to four Telex (or whatever) receiver inputs.

What do you do if you have less than 4 zones and/or less than 4 comm units? Do you insert 50 ohm terminators in all empty ports?

Thanks, and sorry to bring the feed back up after months of burried. I'm myself in the process of buying used Mini-Circuits stuff in the internetz: waiting for a directional coupler to arrive...

Cheers,

Diogo
Title: Re: Antenna splitters
Post by: Lyle Williams on May 20, 2016, 05:38:41 AM
ZFL-1000 is 17dB gain, passive attenuator/filter/splitter are about 10dB loss.

Unused ports should be terminated as best practice, but when was the last time you saw a home TV splitter with terminated ports?  :-)
Title: Re: Antenna splitters
Post by: Jason Glass on May 20, 2016, 09:16:59 AM
Hi Jason,

So, if I'm getting this right...

this seems to be a device with 4 inputs; four zones, and therefore four antennas. The input is a passive combiner.
Then you have a BNC connection after the combined input for filters and attenuators. How much loss do you incurr here, usually?
You then amplify this (I suppose because of split, atennuator and/or filter losses) 20dB as seen in ZFL-1000VH spec sheet. Isn't this too much?
Then you feed this signal to up to four Telex (or whatever) receiver inputs.

What do you do if you have less than 4 zones and/or less than 4 comm units? Do you insert 50 ohm terminators in all empty ports?

Thanks, and sorry to bring the feed back up after months of burried. I'm myself in the process of buying used Mini-Circuits stuff in the internetz: waiting for a directional coupler to arrive...

Cheers,

Diogo
Hi Diogo,

Lyle nailed it!  Although my fastidiousness mandates that I always terminate all unused ports. ;-)

Edit: Actually, each four-way split/combine loss is 6dB, so total losses through the passive parts of the rig end up around 12-15dB depending on the inserted external device(s).

Usually I insert rotary stepped attenuators at each input so that I can adjust each zone's sensitivity, prevent amp input overload, and assure that the system output is not too hot for the receivers.

Sent from my mobile phone. Please excuse the inevitable spelling and grammatical errors.
Title: Re: Antenna splitters
Post by: Russell Ault on May 26, 2016, 05:06:40 PM
Just to provide a quick update on the DIY antenna distro using CATV distro amps:

I haven't yet been able to track down a VNA to actually test the rig out on, but the initial results have been very, very promising. As I suspected, the advantages of getting the antennas out of the rack and into close-to-ideal positions have entirely made up for any disadvantages of not using an off-the-shelf solution. Since the distro system was installed in the rack, the wireless rig has performed with zero on-stage drop-outs for rehearsals and two performances totalling several hours of use, which is a far cry from the drop-out every 10-15 minutes (or worse) I was getting before. Only time will tell if this continues, but so far I'm very, very happy with the results.

If I can find someone with a VNA in town I still hope to test this thing out properly, and I'll post back with the results if/when that happens.

Thanks again everyone for the advice!

-Russ
Title: Re: Antenna splitters
Post by: Keith Broughton on May 26, 2016, 05:48:44 PM
Just to provide a quick update on the DIY antenna distro using CATV distro amps:

I haven't yet been able to track down a VNA to actually test the rig out on, but the initial results have been very, very promising. As I suspected, the advantages of getting the antennas out of the rack and into close-to-ideal positions have entirely made up for any disadvantages of not using an off-the-shelf solution. Since the distro system was installed in the rack, the wireless rig has performed with zero on-stage drop-outs for rehearsals and two performances totalling several hours of use, which is a far cry from the drop-out every 10-15 minutes (or worse) I was getting before. Only time will tell if this continues, but so far I'm very, very happy with the results.

If I can find someone with a VNA in town I still hope to test this thing out properly, and I'll post back with the results if/when that happens.

Thanks again everyone for the advice!

-Russ
Just to confirm, you used remote antennas AND the CATV splitters.
Looks like the remote antennas were the solution to your problem and you still have no actual comparison of the CATV and "pro" splitters.
The differences may come out in tough RF conditions that your situation doesn't provide.
Nice to hear you have a solution though :)
Title: Re: Antenna splitters
Post by: Russell Ault on May 26, 2016, 06:00:33 PM
Just to confirm, you used remote antennas AND the CATV splitters.
Looks like the remote antennas were the solution to your problem and you still have no actual comparison of the CATV and "pro" splitters.
The differences may come out in tough RF conditions that your situation doesn't provide.
Nice to hear you have a solution though :)

Yup, I'm using Sennheiser antennas (an omni close to the rack and an LDPA + 100' of RG6 for the far side of the stage) that feed into the CATV distro amps, and the improved antenna location has done wonders. It's not a real comparison of CATV vs pro audio RF equipment, except to say that both appear to get the job done for this application (i.e. both would be enough rig for the gig). Things might start to suffer a bit under duress (especially in the absence of any real filtering at the distro), but I'd start by blaming the wireless equipment itself (which I'm not a fan of) rather than the distro. In any event, the group that owns the rig tends to require clients to provide "proper" RF when the gig demands, so I'm not too concerned.

If nothing else, I can say with some certainty that my 8-way antenna distro has fewer active stages than almost all the standard commercial offerings! :D

I'll update this thread if I run into any problems down the road, or if I can find someone with a VNA to (dis)prove my admittedly unscientific "real world" results.

-Russ
Title: Re: Antenna splitters
Post by: Lyle Williams on May 28, 2016, 06:33:55 PM
Googling active CATV splitters I find that input IP3 values are typically 20 to 24dBm.