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Author Topic: Antenna splitters  (Read 10356 times)

Russell Ault

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Re: Antenna splitters
« Reply #30 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
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Lyle Williams

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Re: Antenna splitters
« Reply #31 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.

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Diogo Nunes Pereira

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Re: Antenna splitters
« Reply #32 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
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Diogo Nunes Pereira
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Lyle Williams

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Re: Antenna splitters
« Reply #33 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?  :-)
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Jason Glass

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Re: Antenna splitters
« Reply #34 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.
« Last Edit: May 20, 2016, 01:06:31 pm by Jason Glass »
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Russell Ault

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Re: Antenna splitters
« Reply #35 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
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Keith Broughton

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Re: Antenna splitters
« Reply #36 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 :)
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Russell Ault

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Re: Antenna splitters
« Reply #37 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
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Lyle Williams

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Re: Antenna splitters
« Reply #38 on: May 28, 2016, 06:33:55 pm »

Googling active CATV splitters I find that input IP3 values are typically 20 to 24dBm.




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Re: Antenna splitters
« Reply #38 on: May 28, 2016, 06:33:55 pm »


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