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Antenna Distros in the bag


Tim Hays

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I am interested in the same setup Jong. I own three Srb and so I would need six cables with angled connectors SMA to connect the receiver to the distributor PSC.

 

But in this case I would use only three of the eight connectors for each antenna. There should be a terminator load in the other connectors empty?

 

Sergio.

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  • 3 months later...

attachicon.gifImageUploadedByTapatalk1365333047.837019.jpg

Here's my antenna distro. RF pass thru from the VRField into 2 Mini-Circuits RF amps and 8 Way splitters.

Im trying to figure out what is better the invest in a VRField or keep going the srb route and then just set up antenna distro. Never set up antennas for my bag before. So was hoping you might have more info or pics that could help me piece together everything I would need to get. Any feedback would be great! Thanks. Also was thinking of trying out the RFVenue Diversity Fin Antenna just to save on space and money. But still not sold its the best route to take and have also been reading up on that.

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Nice one Michael!

I'll post some photos when I have a chance.

Sergio, you would not need terminators for unused spots. Fortunately for me I've never had to connect eight RX to the PSC, but I've done six a few times. On the show that I do I generally use three. The range I get is fantastic.

I purchased the components found on Texas sound guy's blog to use as a backup in the event that my PSC fails (which it has not done since it received its update from the mother ship), which was the subject of my letter to Larry.

The one thing that I find interesting about both setups is that in both cases the amp is located after the BNC run. Seems to me that it should be up on the fins before the BNC cables to push an amplified signal though and not amplify any noise picked up along the length of the cables.

In my setup the cables aren't very long, so I doubt that it matters too much. One thing that does matter however is that you need to use the same length cables for each antenna.

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Just some general comments:

1. A good combiner/splitter will tolerate unterminated ports or shorted ports. In a perfect world you would terminate the ports but you probably couldn't tell the difference in the field.

2. The usual LPDAs from us and others are not that directional. They will work well at + or - 90 degrees off axis, particularly if the talent gets closer as they move to the sides. The only real dead zone is at the rear. Data sheet here:  http://www.lectrosonics.com/file/426-alp-series

3. The amp should be at the antenna unless the cable is short, i.e., the cable loss is low, such as 1 to 2 dB. Loss before the amplifier can never be made up. It adds directly to the noise figure.

4. Cable lengths can be different, since the diversity doesn't care. The signals at the antenna are kinda random and random plus 3 feet is still just random. Unless one cable is so long that you get large losses.

 

Best Regards,

Larry Fisher
Lectrosonics

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Dont mean to go off topic however wasn't able to find much about the 211 and dipole antennas & distro. I read one antenna is needed per receiver. I wanted to know if there is a benefit to getting 2 dipoles for the 2 receivers in my bag.

I just bought those units and i intend to keep them till i can upgrade to SRBs.

My other question will i in fact need a distro too and will the dipoles give a significant advantage by using them on the bag.

Thank you

Sent from my iPhone using Tapatalk

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Do you mean- 1 whip and 1 dipole per receiver?

You won't hurt anything, but you won't likely experience and improvement either.

Dont mean to go off topic however wasn't able to find much about the 211 and dipole antennas & distro. I read one antenna is needed per receiver. I wanted to know if there is a benefit to getting 2 dipoles for the 2 receivers in my bag.

I just bought those units and i intend to keep them till i can upgrade to SRBs.

My other question will i in fact need a distro too and will the dipoles give a significant advantage by using them on the bag.

Thank you

Sent from my iPhone using Tapatalk

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Rf venue antena: I still don't get how you can have a proper tuning (and boost) with the "dipole" part of the antenna if you're using, say, receivers 4 blocks away from each other... I guess only the "lpda part" of the antenna would be doing the job most of the time... How is diversity achieved then ?

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I have tried many different things when it comes to antenna system and distro for a bag ( LPDA, dipole, coaxial dipole, mini-circuits and Psc rf multi ). The real benefit comes from remoting the antennas up in the air and removing as many obstacles in between the antennas of the receivers and the transmitters, regardless of what you use, this is what gives you better reception. Indeed LPDA have better signal reception by a couple of Db, dipoles works great in situation where you are moving ( car chase, etc ). As far as distros, a correctly engineered mini-circuits/lectro UFM rig is the same as a PSC rf multi.

It is my experience that unless you can move the antenna up in the air over everybody head ( no really practical for a run the gun gig ) or that you can mount LPDA on your bag, you will not experience a lot of gain by doing it over whips. Now this is thinking that your bag is correctly frequency coordinated and that your recorder is not spraying a lot of RF. I use a 664 which is really clean, I have a 3x SRA ( 22-24-26 ) as talent receivers in the bag and 2x LMA block 470 as camera hop transmitters. This is correctly spaced and coordinated and gives me no real trouble for shoots. When I need more range then what the camera can shoot with a sensible lens, then I get my PSC rf multi out, a small tripod and my two Lectro LPDA. Range then triples if not more but I am stationary.

My two cents

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I think another thing to keep in mind when dealing with an RF distro setup is to minimize your cable loss from antenna to receiver input. I see some posts above where multiple adapters, elbows, patches, and excessively long cable lengths are in use. All of these attenuate the signal some. Best to use the shortest cable possible and no adapters. From what I understand, the type of cable makes a big difference as well and each cable type has a different loss spec listed in dB per foot. You'll notice that the longer antenna cables that lectro supplies are much more expensive than rg58 and this is due to the better spec.

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post-2650-0-83124900-1375984340_thumb.jp

 

Here is a shot of what my bag normally looks like on the road for a show that I do. Just three wireless, and of course I keep a couple spares in my peli along with all the cabling just in case. This setup works amazingly well, and no need for caps or terminators on the unused SMA connectors on my PSC.

 

post-2650-0-62145300-1375984840_thumb.jp

 

Here is a shot of me on the road using my system with the antennas up in the air. A combo of a PSC sharkfin and Lectro dipole really seem to be the winning combination, as more often than not, the cast will wander off into the woods and up/down mountains and out of view. With this combo I get a maximum of range and I wont lose reception if they go too far left or right, as I can use the reception meters on the Lectro RX to gauge where the cast is.

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In the photo above, which was the first season of the show, I am using a 411a, 411, and 211. They all worked great.

I have recently been using an SRb in place of the 211 system, and although the PSC system increases the performance of the SRb, it is still no match for a 411 or 211, though the quality if the audio of the SRb has been argued to be better than the 211.

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JonG, I like the setup. That is the way of taking advantage of an antenna system in a bag. I would add that also having a set of coaxial dipole ( a set of dipole made with a piece of coaxial cable ) ready in case you need to get mobile and small again.

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In which mode?

400? Dual? Many modes to choose from...

 

 

How do you have the antennas attached to you?

For this show I have them mounted on a stereo t-bar up on my boom pole. There is no booming in this show since I have to be so far away from the cast (first person shooter, plus lots of go-pros and other types of cameras pointed every which way). So I basically just hold the ol' boom up and rotate it around to get the best reception. I wish I could find a good way to mount these without having to hold the pole, which is why I tried out the setup in the first photo I posted on this thread, which has the two Shure omni dipoles mounted to the sides of my bag (again with the same stereo t-bar, but this time it ran underneath my RX). I was hoping that I could get something "better than what the standard whip antennas would give me", but alas this was not the case, as I got basically the same reception as I would have with standard whips. However, if mounted higher, I am confident that reception would have improved a good deal.

 

pvanstry, I am definitely considering trying out the coax antenna idea. Ive seen a few people do it and they seem to be happy with that system, though I don't see anyone jumping for joy over it. Either way, it cant hurt exploring.

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JonG, the coax dipole are ok.  They give you an easy and portable antenna design but they have very little advantage over the 1/4 wave whip unless they are mounted up high and away from obstacles.  I see them as a way of being able to run an LPDA set when possible and then having the option of going mobile by disconecting the LPDA's and going to them.  Once mounted on your shoulders or anywhere else around your body or bag, they really don't give you more then the Whip's.  But they are really fast to connect since you are running a distro and dicontecting every cables to put the whips back on is long and messy.

 

My experiences.

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JonG, the coax dipole are ok.  They give you an easy and portable antenna design but they have very little advantage over the 1/4 wave whip unless they are mounted up high and away from obstacles.  I see them as a way of being able to run an LPDA set when possible and then having the option of going mobile by disconecting the LPDA's and going to them.  Once mounted on your shoulders or anywhere else around your body or bag, they really don't give you more then the Whip's.  But they are really fast to connect since you are running a distro and dicontecting every cables to put the whips back on is long and messy.

 

My experiences.

Coax antennas look like a great option for changing over from cart antenna to bag antenna quickly but only if your receivers are in the same block, no?  Or at least within a couple blocks? 

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