Jump to content
LarryF

Simple antenna distribution 4 way bag setup

Recommended Posts

This question was sent to me and I posting it for general info.

Hi Larry, [snip]

I am about to go out on the road for a show that requires me to have insane distance for my wireless. Last season, I mounted a passive sharkfin and a dipole on a "t-bar" for stereo miking up on my boom pole and ran bnc cables to a [snip] distribution amp. [snip]

Since I have sent it back, it has worked fine, but the success of the show really does rely on my ability to get a lot of range from the wireless. I am using SMQVs at 250mW, and four 411s.

My question is, what kind of a system would you recommend using the splitters and amplifiers that Lectro makes for my bag? Ive seen then and Ive seen people use them, but I don't know how they are implemented; i.e. would I put a UFM 230 somewhere in the mix (my bnc cables are only 14'), before or after a mini circuits splitter? I'm just not entirely sure how I would go about wiring that sort of setup.

Thanks for your help!

Jon

Hi Jon,

You will have about 9 dB of loss, assuming your 14 foot cable is RG58 type (5mm or 0.2" size). Fourteen feet will have 1.7 dB of loss and the 4 way splitter will be about 7 dB. This is enough loss that you need an amp at the antenna for maximum range. Given that you are even talking about maximum range, then the surrounding environment must be fairly RF quiet. Again, this says you need an amp at the antenna.

The ideal setup would be two sharkfins with a short cable to a UFM50 (UFM230) to your 14 foot cable back to an inline bias T http://www.lectrosonics.com/85-BIAST/View-details.html to get power up the cable to the amps or you will need to run lightweight DC power cable up to the amps. This power cable can be light weight zip cord from 18 to 24 gauge. It can be zip tied to the coax. Set the amps for 8 dB since that is the closest to your 9 dB of loss. From the bias T or from the 14 foot cable, go into the MiniCircuits 4 way splitter to one of the 411 antenna inputs. Wash and repeat for the other antenna and go to the other input on the 411's. Oddly enough, this diagram on the Lectro site shows your setup (without a bias T):

http://www.lectrosonics.com/182-UFM230/View-details.html

Best,

Larry F

Lectro

Share this post


Link to post
Share on other sites

" a show that requires me to have insane distance for my wireless "

" the success of the show really does rely on my ability to get a lot of range from the wireless. "

aka: unreasonable expectations

and a good time to discuss appropriate payments!

Share this post


Link to post
Share on other sites

The ideal setup would be two sharkfins

Read the spec sheets on your sharkfins. Only 4dbd gain? Wouldn't yagis be a much better and cheaper solution?

Share this post


Link to post
Share on other sites

Read the spec sheets on your sharkfins. Only 4dbd gain? Wouldn't yagis be a much better and cheaper solution?

Bandwidth, gain, size: pick any two. Yagis can have more gain in the same size antenna but have narrower bandwidth. They need to be matched to the block (or two) you are using. Log periodics with wide bandwidth and moderate size have low gain, i.e., 4 dB. But yes, Yagis can be good choices matched to the frequency block(s).

Best,

Larry F

Lectro

Share this post


Link to post
Share on other sites

Hi all

This is one of the better explanations that I've seen for the various antenna designs and theory's.

It may help, it may not, but I sure learned a lot from watching it...

Rgd's

Andrew

Share this post


Link to post
Share on other sites

Andrew

I didn't watch all the video but a typical yagi pattern has side and back lobes and will look more like this than the linear graphics in the video.

sample-radiation-plot-of-a-typical-Yagi-antenna.png

Share this post


Link to post
Share on other sites

perhaps...

At 560mhz, a 2 wavelength yagi would be around 45 inches and deliver 14 db of gain.

Of course as Larry said the trade off is bandwidth.

Optimally use more antennas and dump the power divider.

Without the power divider the need for a LNA at the antenna is debatable.

Now the trade off is how much gear do you want to pack and set up.

Share this post


Link to post
Share on other sites

At 560mhz, a 2 wavelength yagi would be around 45 inches and deliver 14 db of gain.

Of course as Larry said the trade off is bandwidth.

Optimally use more antennas and dump the power divider.

Without the power divider the need for a LNA at the antenna is debatable.

Now the trade off is how much gear do you want to pack and set up.

Definitely the 4 way splitter is the loss culprit. Without it, as you say, there is little need for the amps. The best amps will add a little noise to the antenna signal and another possible place for intermod. So with only 1.8 dB of cable loss, the amps would do as little good as harm, but both small.

Cheers,

Larry F

Lectro

Share this post


Link to post
Share on other sites

Expectations will keep getting higher. Its is our job to meet them. That is why TC recording at the source "transmitter" is something I can not work without. I bet in the future the TX recording will be a tool that all of us will have to have.

Share this post


Link to post
Share on other sites

I bought the TRX-RX system a few years ago exactly for that reason, BUT Tx recording has proven, for me, to be almost never used in the end since most of the documentaries or shows I did wouldn't take the time to manage the files of these ''additionnal'' memory cards (load of files) I lended to them. It's more of a backup plan than anything else and since I get way more range with my 411 kits i usually get more usable audio in the end, *practically* speaking on a day to day basis (leaving *theory* and brochures on the side).

Fact is, they ask for more on our side of the chain, but they also cut a lot on time for post, at least here where I live and work so these separate files you give'em, well, you figure.

An other thing to think of is the additionnal work you have to actually manage these files; I did tell post houses to download Zaxconvert so they do all the job because charging for this half hour wasn't always, mmm, possible (but curioulsy it was for post, go figure; maybe they ended up not using the files or just try to find the good ones when there was a hiccup, I don't know and don't care).

Where it's practical now, is using for camera send in a small package as a backup (plus it's with timecode; very good!) : 302 (with occasionnally a MixPre-D if needed) plus TRX-STA is the best way to go compact... For now.

They announced the Maxx, let's see what the competition brings in april too.

Share this post


Link to post
Share on other sites

I bought the TRX-RX system a few years ago exactly for that reason, BUT Tx recording has proven, for me, to be almost never used in the end since most of the documentaries or shows I did wouldn't take the time to manage the files of these ''additionnal'' memory cards (load of files) I lended to them. It's more of a backup plan than anything else and since I get way more range with my 411 kits i usually get more usable audio in the end, *practically* speaking on a day to day basis (leaving *theory* and brochures on the side).

Fact is, they ask for more on our side of the chain, but they also cut a lot on time for post, at least here where I live and work so these separate files you give'em, well, you figure.

An other thing to think of is the additionnal work you have to actually manage these files; I did tell post houses to download Zaxconvert so they do all the job because charging for this half hour wasn't always, mmm, possible (but curioulsy it was for post, go figure; maybe they ended up not using the files or just try to find the good ones when there was a hiccup, I don't know and don't care).

Where it's practical now, is using for camera send in a small package as a backup (plus it's with timecode; very good!) : 302 (with occasionnally a MixPre-D if needed) plus TRX-STA is the best way to go compact... For now.

They announced the Maxx, let's see what the competition brings in april too.

if the production requires extreme range they should be prepared to the the extra work. My situation is different since we have an on location media manager/editor who I trained how to use zaxconvert and waveagent. But even on other jobs I do on the side I spend an extra 10 minutes to convert and deliver. As far as range: I get better range then 411 with my current setup - trx900la,qrx100 in single mode, going in to micplexer and dipoles. But that is a different story...

Share this post


Link to post
Share on other sites

I would love to do that! Been to the Lectro site... But trying to work this out and purchase something while I am on this job. Anyway, figuring it out on my own, but if he is around to advise, I am receptive... :)

Share this post


Link to post
Share on other sites

Hi Denielle,

1. We always enjoy visitors and, I assure you, the brain picking goes both ways. We aren't far away and I think you could pick up enough info about our products and RF in general to make it well worth the trip. If it is anytime around noon, you can probably get lunch out of us too.

 

2. I've have always liked the UFM50 as it has a narrower front end but users by far prefer the UFM 230 because it can be used with almost any blocks. The UFM230 can be made to duplicate exactly the narrower bandwidth of the UFM 50 by using one of our passive filters in front of the unit.  See the PF25 and PF50 in the link below:

 

http://www.lectrosonics.com/In-Line-RF-Amplifiers/

 

If I have to give one answer, I'd have to recommend the UFM 230 because of its greater flexibility. It uses a very strong amplifier and is very resistant to intermod and overload even if it is wide band.

Best Regards,
Larry Fisher
Lectrosonics

Share this post


Link to post
Share on other sites

>if the production requires extreme range they should be prepared to the the extra work<

I have not noticed production ever stepping up in this way

Share this post


Link to post
Share on other sites
 If it is anytime around noon, you can probably get lunch out of us too.

 

I can attest this. Every visit I have made to Rio Rancho over the years have included a visit to a good eatery or two. I think these guys use going to work as an excuse to go to lunch every day. ::)

Share this post


Link to post
Share on other sites

Create an account or sign in to comment

You need to be a member in order to leave a comment

Create an account

Sign up for a new account in our community. It's easy!

Register a new account

Sign in

Already have an account? Sign in here.

Sign In Now

×