The question of passive or active antenna distribution - jwsoundgroup

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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!

"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

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. 

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. 

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....

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.

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 

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.

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.

I've been looking over past discussions on the topic of antennas and active and passive combiners but still feel a bit in the dark and am hoping for some more discussion.

What I am looking at for the cart I am building is a stand alone unit that will distribute 2 Dipoles or LPDAs to 4-6 Lectro 411's

I often need to take receivers out for bag work so am looking at these 4 options:

A) 2 x PSC RF Multis (1 per Antenna)

Lectro UMC16BL Rack mount ADA

C) Audio Technica half rack unit ATW-DA49

http://www.audio-technica.com/cms/accessories/b2f1e766e2abec42/index.html

D) 2 x Mini Circuit 4 way passive splitters

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I am quite intrigued by the Audio Technica unit, they seem to go for around $400 but am not sure if the Lectro equivalent UMC16B is better or not, hoping some users can comment!

Hi Johnathan,

I'd feel better about the AT's if they gave some performance specs. Distribution amps lead a hard life since users have pretty well made the manufacturers go to wideband units. This means the distribution amp will see every RF signal between DC and light (440 MHz to 900Mhz for the AT, 450 MHz to 900 MHz for the PSC), including any 50kW TV stations that are in the locality. Because of this, you'd like to have a distribution amp with a tough RF amplifier as well as low self noise. Neither AT or PSC specifies 3rd order intercept which is the universal measure of overload and/or intermod resistance. They may be great but without specs how can you tell? They do have the distinct advantage of being more "reasonable" in price. Also, both the AT and PSC units are made for all markets rather than the U.S. market which currently is 470 MHz to 700 MHz. Letting the upper end go out to 900 MHz is not wise, IMHO, because of more and more garbage in the 700 to 900 MHz area.

Obviously, I am biased here, but partly because I know what goes into the Lectro units. A lower cost suggestion would be to use one of the other two units units and put one of our passive filters (PF25 or PF50) in the antenna line before the distribution amp antenna input. That will cut down tremendously on the unwanted RF going into these units. That will restrict your operation to one (PF25) block or two (PF50) blocks. You can select different filters if you move around and match the filters to the blocks you will be using. That isn't a bad idea also for our distribution amps if you can stand 25 or 50 MHz of operating bandwidth.

The Mini-Circuits passive splitter won't have any overload or intermod problems but you will have 6 dB of overall loss. If the talent is relatively close to the antennas, this is workable. It is equivalent to cutting the transmitter power by four or doubling the antenna to transmitter distance. It is a solid low cost alternative with the provisos above. In really noisy urban environments, this loss may not even be noticeable since the loss affects both the signal and the noise.

If this has created more questions than answers, ask on.

Best,

LarryF

Lectro

I've been looking over past discussions on the topic of antennas and active and passive combiners but still feel a bit in the dark and am hoping for some more discussion.

What I am looking at for the cart I am building is a stand alone unit that will distribute 2 Dipoles or LPDAs to 4-6 Lectro 411's

I often need to take receivers out for bag work so am looking at these 4 options:

A) 2 x PSC RF Multis (1 per Antenna)

Lectro UMC16BL Rack mount ADA

C) Audio Technica half rack unit ATW-DA49

http://www.audio-tec...ec42/index.html

D) 2 x Mini Circuit 4 way passive splitters

I am quite intrigued by the Audio Technica unit, they seem to go for around $400 but am not sure if the Lectro equivalent UMC16B is better or not, hoping some users can comment!

I have been using the Mini-circuits 4-way passives for a while now with great success. They are used only with my cart really, but were easy to adapt anywhere on the cart from their small size. I have them feeding x2 411's and an SRa. If I knew about AT's multi-coupler at the time, I might have gone with that instead, being that it says it includes cables as well. I've heard some bad reviews from those that have used the smaller PSC Multi boxes, however their Multi-Dual is excellent. Given that you're wanting to feed up to 8 receivers, I think you'll be better off getting like a PSC Multi-Dual, or the Lectro UMC16B, using a passive splitter with more than 4 outs seems to be too great of a loss.

Thanks for the replies gentlemen:)

Larry I was hoping you would throw in a word or two. I did feel like specs were on the vague side with the AT and PSC RF Multi units and I did download the UMC16B manual and noted the 3rd order intercept etc

Seeing as I will be operating 4 UCR411s on my cart for now but later would like to expand to 6 and more it does seem wise to go with a unit that can grow with my cart so to speak.

So I will probably go with the UMC16B. I am operating on block 22 and 24 is there a filter that can operate from 563 - 638Mhz or can that pass band be custom ordered built in to that unit?

Also regarding antennas, I have read that 1 dipole and 1 LPDA can work well with a diversity system. Any discussion on antenna types would be interesting

Hi Johnathin,

We don't have a 75 MHz filter. As filters get wider, the out of band rejection gets worse anyway. Split blocks is a good reason for a strong distribution amp. If you are going to 6 channels, then the extra outputs of the UM16B makes sense. You don't need to terminate unused outputs, by the way.

My recommendation is to use two similar antennas. The SNA dipole will stretch to cover 22 and 24. Simply set them for block 23. They are compact and easy to mount up in the air where you can get excellent range.The LPDA has sligthly more gain (+4 dB) than the dipole with more back rejection, but not as portable. They also cost more bucks. There are some other sharkfin LPDAs on the market and while they may not be as brute strength rugged, are still strong, good performers and very good buys. The ventilated units are better outside if wind is a factor.

There is nothing wrong with first buying the dipoles. The price is good and e,ven if you end up with LPDAs or other directional antenna at some point, the dipoles are still a handy part of your kit.

Best,

LarryF

Lectro

Thanks for the replies gentlemen:)

Larry I was hoping you would throw in a word or two. I did feel like specs were on the vague side with the AT and PSC RF Multi units and I did download the UMC16B manual and noted the 3rd order intercept etc

Seeing as I will be operating 4 UCR411s on my cart for now but later would like to expand to 6 and more it does seem wise to go with a unit that can grow with my cart so to speak.

So I will probably go with the UMC16B. I am operating on block 22 and 24 is there a filter that can operate from 563 - 638Mhz or can that pass band be custom ordered built in to that unit?

Also regarding antennas, I have read that 1 dipole and 1 LPDA can work well with a diversity system. Any discussion on antenna types would be interesting

I must chime in here and say when I got my initial high-gain antennas I went with the PSC multi-dual with the PSC sharkfins. (The UMC16BL was not to be available for a few years.) Then I got PW helicals and boy what an improvement in performance, but I would still see some "noise" (little blips in the RF spectrum display on the 411s) when I turned on the Comtek BST-216, and also the Lectro T4, which was two full blocks away from any of the 411s.

Then I decided to get back ups of everything, and instead of another PSC multi-dual I went with the Lectro UMC16BL for my eight 411s. I am so happy I did. I saw a dramatic increase in signal strength / range and zero noise when I turn on other wireless devices (or put their antennas) right in front of the helicals. I run them up to 100' (only on RG8 cable of course) when I have to, but usually they live on the cart on 15' RG8 cables. But I will still keep the PSC Multi_Dual as a back up; after all I had several successful years with it.

Dan Izen

I've been looking over past discussions on the topic of antennas and active and passive combiners but still feel a bit in the dark and am hoping for some more discussion.

What I am looking at for the cart I am building is a stand alone unit that will distribute 2 Dipoles or LPDAs to 4-6 Lectro 411's

I often need to take receivers out for bag work so am looking at these 4 options:

A) 2 x PSC RF Multis (1 per Antenna)

Lectro UMC16BL Rack mount ADA

C) Audio Technica half rack unit ATW-DA49

http://www.audio-technica.com/cms/accessories/b2f1e766e2abec42/index.html

D) 2 x Mini Circuit 4 way passive splitters

I am quite intrigued by the Audio Technica unit, they seem to go for around $400 but am not sure if the Lectro equivalent UMC16B is better or not, hoping some users can comment!

I recently redid my whole antenna set up and got the shure equivalent of the above audio tech unit, I got the whole kit including 2 x active sharkfins from BH Photo for about $. In practice the rig works very well and I would happily recommend it, I currently use it to feed 2 x Zaxcom QRX's and a Lectro venue. The only bad thing I'd say is the shure sharkfin antenna are quite flimsy and thin, they have a high wind rating but I'm yet to test that as to date all their use has been studio based.

Through a bit of a communication error I did end up importing 2 complete systems so have one for sale if anyone local (NZ or Aussie) is reading, if you're in the US got to BH, they have the best price.

Regards,

Chris.

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