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Is there a strength cutoff for a wireless set to work in a specified band?


MattinSTL

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So you look at the frequency map on lectrosonics and sennheiser... you see there's a TV channel with 15kw tower in your frequency, but it's 60 miles away. Let's say you have a lectro set with one frequency in the middle of that band. Will it be crystal clear or will you only hear that TV station through the receiver? How do you know? Normally I look for channels in a "vacant" block... but what's the cutoff?

Is there a hard number here? Can you expect clean audio even if you're in the middle of a weak TV channel?

I've worked with 411 many times and rarely had to seek out a new channel for clear audio... Let's say I find a bargain 195d for backup, but the frequency is in the middle of a weak band and NOT in the band of the 100kW plus big stations... will it most likely be clean in reasonably close proximity?

What power kW and mileage is the deal breaker for shared bands?

EDIT: Obviously I aim for the "vacant" bands... but as the charts show this distance and signal strength of each band (vs. simply yes and no) I'm assuming there's a strength where even though a band shows occupied, the strength and/or distance is irellevant to the performance of a wireless set that's used in less then 50' distances?

Say Lectro 100mW transmitter in the dead-center of a 15kW TV station (which is very weak for a TV channel, but obviously way stronger then the 100mW)... AT 60 miles away?

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"Will it be crystal clear or will you only hear that TV station through the receiver? "

it depends...

but...

almost all TV stations today are digital, and their signals will not be "heard" on your Lectro RX's, rather. the RX will experience a higher noise floor, the digital signal, which is 6 mHz wide, and thus reduced range...

" Is there a hard number here? "

no

" Normally I look for channels in a "vacant" block... " + " a lectro set with one frequency in the middle of that band. " + " the frequency is in the middle of a weak band and NOT in the band of the 100kW plus big stations... "

wow, your terminology is confusing me... these terms have specific meanings and are not interchangeable..

The Lectrosonics wireless mic guide is required reading, and check the FAQ's, too...

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I don't think you can really tell without doing a scan and trying it. I had a shoot the other day where I was in the back of a limo for a driving scene for which we had to use wireless mics, and we encountered long stretches of Hollywood, West Hollywood, and Beverly Hills that were perfect... and then we'd get slammed in a specific area for about 100 or 200 yards. So it's impossible to say whether the TV transmitter will swamp the wireless frequency or not without actually checking it.

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Thank you very much Senator and Marc! I appreciate your time to answer. I'm sorry, but I should have stated this was in relation to old, fixed frequency units vs. new Lectros.

Senator... I've been using Lectro 411s where I can scan for a channel, but those units are not my own. In the past I've also had good luck with lower models, that can be found pretty cheap on occasion. Recently I came across two CR190's for peanuts. One set was dead center of a vacant band here in STL (Saint Louis). The other was in a lower powered TV station's band. I bought the one that was in a clear band, and skipped the other.

My typical use for wireless is for convenience, when a production is moving really quickly and I have to pop a lav on and off people in about a minute... and we stay in close proximity. Of course I always have redundancy with boom on ch 1.

I realize the obvious answer is $2500 per channel 411 or Zaxcom for as guaranteed as wireless gets, and with any "serious" production I'll still be using 411s if not hardwired.

For lower budget stuff, (or even my own job), I'd still like to have extra wireless sets available, and I wondered if having any TV station as showing on the chart means a TX will be overpowered... or if there was a strength where you pretty much would know it wouldn't matter... i.e. this CR190 is very clean (so far) that I'm tempted to pick up a couple more... and I'm wondering if I should only consider units in a totally vacant band, or if the 100mW TX is enough to be clear even if it's in an occupied, but weak TV channel.

I think you've answered my question well however... especially since I'm already gambling on a unit with only one frequency. I'm going to avoid any extra risk on the issue. I've got several Sennheiser G series sets, but I only use them on lower budget stuff too... as the noise floor is higher then I'd like. If I had a bunch of cheap Lectros with their low noise floor... I'd probably use wireless more then I have been.

(I have a friend who I may be running sound for, for a doc in the Himalayas... and while I'm guessing ANYTHING will have a clear signal there, I'd like to be able to use the set afterwards too... and the rugged build of Lectro, even their older stuff... would inspire confidence in that situation.)

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" dead center of a vacant band "

you need to learn the correct terminology for this stuff...

I had to reread both your posts several time to fugure out that you meant vacant TV channel.

Now that you have explained, and I have figured out some of your terminology, your results in your city with the second 190 series unit will be variable, depending on your exact location.

Keep in mind, that Television broadcasters are only a small part of the overall interference picture, which varies from place to place, and from time to time...

" but I only use them on lower budget stuff ..."

I don't agree with that as a philosophy. If it is what you have and it works, use it.

keep in mind that of it works, no one listening to the finished product will be able to tell just by listening to it what brand, or price it was...

I demonstrate that to my students, and point out that the Senn Evolution series wireless is an excellent value, and a cost effective option. You have probably heard lots of stuff recorded using them, as they have been a popular alternative and thousands are in daily use.

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Thank you again Senator. I should probably phrase my questions more carefully rather than typing off the cuff, so to speak. I've had 5 sets of Sennheiser G series and I've used them on some reasonably serious gigs, and whether or not this was wise, I clarified for the client in advance on what they were getting, for what they were paying... and offered to do the gig with all Lectro, and forward the rental cost. They chose the 5 Sennheisers.

I don't put Sennheiser's sound on the level of Lectro, but I'm glad to hear your endorsement of the Sennheisers. I may be selling them short unnecessarily with clients that wouldn't know the difference.

I've been doing sound for the same client for a few months now, and we haven't even broke out the Sennheisers based on the cam-op's criticism of them. (This guy is someone I highly respect and I had no battle to win, and so far our sitiations have accomodated hardwired lavs).

I've got a budget shoot coming up next week where we anticipate run and gun on boom only, but if there's nothing to lose I may put the new Lectro on it's own channel and see how it does.

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Buying fixed freq is risky these days, at least if you may be near any kind of urban area. That's why they are pretty inexpensive. That said, there are still a bunch in use, and if the transmitter isn't too far away, you should be fine in *most* cases.

You can look up the transmission map of a specific transmitter, the FCC has that map, and stations have it in their public access file. IIRC there are a few 3rd party websites that tried to make that info easier to look at.

DigitalTV may be a bit different, but FM radio, and analog TV were very much influenced by geography, and even the time of the year. There is a LOT of math when considering the effective broadcast range of a transmitter, and at the end of the day an engineer (and possibly the FCC) will drive around and do signal strength readings. Those transmission maps are generally where the station is to be at "full signal strength", though the transmission may go well beyond that. Often the extra range depends on how close something else is on that frequency. If it's a bit of a no man's land, then the closest station will get some coverage (or to us, interference).

So your transmitters are usually pretty close to the receivers? For example, a lot of interviews to camera, or lock-off talking head? That close range should make things easier. I don't know what "peanuts" you are finding those old Lectros for, but you could also look at a 200 or 400 series of a Lectro LM transmitter and a 401 (or 201) receiver. New a LMa and 401 should still be under $2000. A few years ago I got a set for about $1,700. If you go to the 200 series used, that should save a good bit and still give you the flexibility of tuning and visual scanning. I don't know if that's out of your budget, but something to look at.

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Marc... I use THE SENNHEISER FREQUENCY CHECKER to try to predict any problems for a base-line. The reason I'm linking it is wow... I didn't realize LA was as packed with signal as it is! I've only done about a dozen gigs there... and I just used what I had for wireless, and scanned for a "clear" frequency. I also had some issues. Jeez, you guys are FULL out there!

Senator, thanks for the reassurance. I did a gig this week that was very run 'n gun, being shot for broadcast... I needed every mic I had and decided to put the Sennheisers into use... you know what? They sounded great and I didn't get a single hit! I probably got lucky... *shrug*... but I was planning to sell them as I convert my bag to all Lectro... now I think I'm keeping them. (Still bought several Lectros this week however).

Thanks again to you guys and JWsound for this great resource of shared experience and knowledge.

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Jeez, you guys are FULL out there!

And sometimes full OF it!

Yes, I have been slammed on occasion, even on Blocks 19 and 21. Almost always, though, I can carve out enough space for as many as 8 wires and 2 channels of camera hop, which is my normal limit to my sanity. Very likely, I couldn't do it without the tracking front end in the Lectro VRT/411's. I also cheat with the camera hops, which I usually run at 250mw.

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