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The question of passive or active antenna distribution


Spin360
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Hello!

I have been thinking of how to get antenna distribution for a few months, but have yet to actually pull through because everybody seems to be telling me something different.

 

What I have is two DCR822 lectros with sna600a (which I plan to replace with betso bowtie), and currently I'm using the antennas just on one receiver. 

I work from a bag.

 

Now, I was told at my local retailer to definitely get a BSRF system, which they sell, because I lose 4dB gain in a distro wlsewise.

But another retailer in Germany (kortwich) that make passive and active systems specifically told me not to go active if I don't plant to use long cables.  My only issue is, that all these distribution systems are huge and if at all possible I would like to shrink down stuff as much as possible.

 

Now in the Facebook group somebody suggested this one:

https://www.minicircuits.com/WebStore/dashboard.html?model=ZFSC-2-2-S%2B

 

Which, if it is the correct one, should be ideal I think?

 

So what I need is advice on what system I should get or avoid...

Should I definitely go passive? Is there a system like the BSRF AS-62 but smaller?

Or should I go active to fix gain lost from distribution?

Thanks a lot!

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"Now, I was told at my local retailer to definitely get a BSRF system, which they sell, because I lose 4dB gain in a distro wlsewise." and they would lose an expensive sale if you don't.

 

Definitely go passive. If you are not running long cables and/or splitters with 10 dB or more loss, passive is the right choice. You will have no intermod in an amplifier (you don't have one), lower current draw, a system smaller and lighter, at lower cost. Furthermore, at 99% of your distances, you will have plenty of signal. 

 

By the way, MiniCircuits is a classic company and their products are so solid, Lectro resells them as an aid to our customers.

Best Regards,

Larry Fisher

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Thank you for the response, Larry!

23 minutes ago, LarryF said:

they would lose an expensive sale if you don't.

Yes, that's is why I mentioned it...

 

 

Would you mind stating which ones to get? I don't mind buying the "resold" ones, since I can easily order them through a store here from you guys.

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2 hours ago, Spin360 said:

 

Now in the Facebook group somebody suggested this one:

https://www.minicircuits.com/WebStore/dashboard.html?model=ZFSC-2-2-S%2B

I completely agree with this (except get the BNC version, that's my personal preference rather than dealing with the slightly more finicky SMA connector. Also, the BNC version is slightly cheaper).  Get two of them, one for each antenna.

 

If you needed to supply power to your antennas and/or have long runs of cable (short runs shouldn't be a problem, say if you're putting your bag on a mini sound cart, and want to run your SNA600a antennas 7ft up into the air for better line of sight, that's fine to do) and/or use even more receivers at once (than simply the 2x DCR822 you are planning to use), then I'd recommend you get something else than the ZFSC-2-2+

 

But for your purposes, sounds like the ZFSC-2-2+ would be perfect. 

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I'm using BSRF AS-62 in my bag, with 1 x Zaxcom QRX, 1 x Wisycom 42, 1 x Audio A10, the BSRF AS-62 itself has power supply for active antenna, but you can turn it off, so in this case it's a passive system. 

 

the AS-62 has no amplifier build in, but only power supply for active antenna, in this case, it's not an active splitter+amplifier system, but a passive splitter with 470-700MHz Bandpass filter. I think you can even unplug the power for AS-62 and it works as a passive splitter (have tried once and it worked).

The Mini-Circuits one has no band-pass filter, which can cause some problems if you are very close to Walki-Transmitter or Mobile-Tower. 

Like the post above mentioned, I would never use active Antenna or use active amplifier in a bag, also Glenn from Zaxcom mentioned that one should not use active Antenna or amplifier with digital wireless systems. 

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7 hours ago, Tong0615 said:

[snip]

The Mini-Circuits one has no band-pass filter, which can cause some problems if you are very close to Walki-Transmitter or Mobile-Tower.

---{LEF -It doesn't need a filter since there is no active devices in the MiniCircuit units to creat intermod or overload} 

Like the post above mentioned, I would never use active Antenna or use active amplifier in a bag, also Glenn from Zaxcom mentioned that one should not use active Antenna or amplifier with digital wireless systems. 

---{LEF- The Lectro amps, active antennas and RF distribution systems have excellent linearity and work just fine with digital wireless systems. However, we have had numerous complaints from users using non Lectro RF amps and distribution systems. It's one of the first questions the service techs ask about in poorly performing digital setups. However, with any amp or distribution system, it is necessary to keep the overall RF gain to reasonable values. For instance, 20 dB of extra gain is about 18 dB too much, even if it is Lectro gain.} 

 

Best Regards,

Larry Fisher

 

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9 hours ago, Philip Perkins said:

This.  My Personal RF Guru (Mr. Bill Ruck) advises against any unnecessary electronics or added cable in an RF system.  Keep it as simple as you can.

 


that make sense, any adding electronic parts could cause problem. but in the real world it’s all about compromise, in the best case would be no RF at all but everything cable. 
 

I would be interested, things like Zaxcom MicPlexer, SoundDevices SL and Audio Wireless DADM, they are all powered RF distributors, I would not assume that all these Products will ruin the RF with their electronics and the capability of powering active antenna. 

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Looking for a splitter solution myself. Now, I have a two double Sony DWX (so also digital) receivers, and i am wondering if it's better to use 2 way ZFSC 2-2+ passive splitter from Mini Circuits with about ~3.5 dB loss, or future proof myself and go for the 4 way ZFSC-4-1-BNC+ already (about 7dB loss)   

 

Larry, am I right that the loss in these expensive active and passive splitters is just  a fact of life, and all they do later is gain up what is left? Sorry If this is obvious, but it's good to reassure the basics sometimes.

Also, the digital systems are not as sensitive to the signal loss as long as there is sufficient distance from noise? So the digital receivers do not have to 'see' as much signal as the analog ones to work alright? 

 

Thank you so much for your knowledge and time folks, I learned so much on this forum.

 

Hope the Senator is fine also....

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6 hours ago, resonate said:

Looking for a splitter solution myself. Now, I have a two double Sony DWX (so also digital) receivers, and i am wondering if it's better to use 2 way ZFSC 2-2+ passive splitter from Mini Circuits with about ~3.5 dB loss, or future proof myself and go for the 4 way ZFSC-4-1-BNC+ already (about 7dB loss)   

My personal view would be to get the ZFSC 2-2+, as if you're using four receivers at once, then you shouldn't really be using a passive splitter. Should get an actual RF Distro instead, such as say the DADM226-DT V2 is very nice with not just a RF distro, but a power distro too, and a selectable filter! https://www.gothamsound.com/product/dadm226-digitally-tuned-diversity-antenna-distribution-module Lots of other options such as a PSC RF Multi or BSRF AS-122 etc etc, check out your local sound store and see what they have to offer.

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I was now also suggested BNC T-Pieces, incidentally I even have one and they cost just a tenth of the mini-circuit parts.

What's the reason for going for the mini circuit parts?

Or do the simple BNC splitters do the same?

Thank you :)

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The MiniCircuit parts split the input power into two outputs, each having half the power. That is why the "insertion" loss is 3 dB or half the power. There is very little loss, it's just split in half (-3 dB). The single input to the MiniCircuit part remains at 50 Ohms even though you are outputing to two 50 Ohm devices so you have an excellent match to the 50 Ohm antenna. Also, the two output ports are isolated from each other by about 20 dB or more, so accidental garbage (local oscillator) on a  receiver input doesn't interfere with the other receiver.

 

The BNC "T" does none of these. The input impedance and output impedances are at best 25 Ohms, there is little isolation between ports to receivers and the losses will be greater than 3 dB. The fact that the antenna and receivers aren't seeing 50 Ohms, may shift passbands or filters of the antenna and receivers. 

 

Now the disclaimer: All these effects may be small (other than isolation) and totally unnoticeable in an environment with good signals. On the other hand, the 2 way MiniCircuit splitter is not very expensive and is the correct solution. However, if I were in a situation where one antenna had to drive two receivers and all I had was a BNC "T" , I'd use it in a microsecond.

Best Regards,

Larry Fisher 

 

 

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50 minutes ago, LarryF said:

The MiniCircuit parts split the input power into two outputs, each having half the power. That is why the "insertion" loss is 3 dB or half the power. There is very little loss, it's just split in half (-3 dB). The single input to the MiniCircuit part remains at 50 Ohms even though you are outputing to two 50 Ohm devices so you have an excellent match to the 50 Ohm antenna. Also, the two output ports are isolated from each other by about 20 dB or more, so accidental garbage (local oscillator) on a  receiver input doesn't interfere with the other receiver.

 

If a MiniCircuit with 3 (or more) outputs was used, but only two of the outputs were hooked up, would each output still only see a -3dB decrease? 

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36 minutes ago, IronFilm said:

If a MiniCircuit with 3 (or more) outputs was used, but only two of the outputs were hooked up, would each output still only see a -3dB decrease? 

I'll let Larry chime in, but I believe with more splits the decrease is there regardless if the ports are used. FWIW - I have both a 2-way and a 4-way, but use the 4-way splitter between 2x SRC in the bag rig, only because the layout of the bag makes this work better in a practical sense with the way the bag is set up (all 3 ports on the 2-way sits on the same side, and the chassis is actually somewhat more bulky). I have terminators on the un-used ports, but apparently this makes no difference (still makes me *feel better* and probably doesn't hurt anything). Works very well for me, but YMMV. I even have the "wrong" length antennas on this rig, but again - no problems for several years... the bag rig of course does the type of jobs where I can be close enough. Always scanning for clean freqs and coordinating with FreqFinder.

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Thanks for the feedback of your experiences @Johnny Karlsson!

32 minutes ago, Johnny Karlsson said:

the bag rig of course does the type of jobs where I can be close enough.

Why then do you use the MiniCircuits as an RF distro of sorts, if you're always close enough, do  you even need a RF Distro?

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9 minutes ago, IronFilm said:

Thanks for the feedback of your experiences @Johnny Karlsson!

Why then do you use the MiniCircuits as an RF distro of sorts, if you're always close enough, do  you even need a RF Distro?

Mostly because it makes the bag more streamlined + the two antennas sit on the opposite sides of the bag, which I also feel helps, even though it's just about a foot vs 3 inches. Also, these whips fold down inside the bag so when the zippers are closed - nothing sticks out.

I'll try to post a picture when I get to it, so maybe it will make more sense than my clumsy attempts to describe it in writing.

 

And even though I said "close enough", I do in fact get decent range with this setup.

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11 hours ago, IronFilm said:

If a MiniCircuit with 3 (or more) outputs was used, but only two of the outputs were hooked up, would each output still only see a -3dB decrease? 

Sorry but no such luck. There are internal balancing resistors that come into play when ports are unterminated or poorly terminated, i.e., not 50 Ohms. You still have a 3 dB loss with a single out but the input is balanced to 50 Ohms.

Best Regards,

Larry Fisher

 

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I bought a pair of the mini circuit splitters from lectro and combined them into a small 2 way splitter that worked wonderfully for me for years.  I sometimes use it to split in front of my micplexer if I need to add a 5th receiver.  If I only needed 2 receivers this would be my go to.

 

PXL_20220605_180156638.jpg

 

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On 5/30/2022 at 2:14 PM, IronFilm said:

I completely agree with this (except get the BNC version, that's my personal preference rather than dealing with the slightly more finicky SMA connector. Also, the BNC version is slightly cheaper).  Get two of them, one for each antenna.

 

If you needed to supply power to your antennas and/or have long runs of cable (short runs shouldn't be a problem, say if you're putting your bag on a mini sound cart, and want to run your SNA600a antennas 7ft up into the air for better line of sight, that's fine to do) and/or use even more receivers at once (than simply the 2x DCR822 you are planning to use), then I'd recommend you get something else than the ZFSC-2-2+

 

But for your purposes, sounds like the ZFSC-2-2+ would be perfect. 

 

Do you think the ZFSC-2-4+ would work equally?

Or is it the BNC version you meant?

Thank you :)

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