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Professional Wireless Checking In


Carl Cordes

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Just a few words to let you know I signed up and will check the pulse of RF discussions from time to time. ;)

I'm the General Manager for Professional Wireless Systems which was founded by James Stoffo. Most of you know us by our Helical antenna which Dan described as lookiong like "something out of Babylon 5" and others called it the "top hat". To my knowledge, the only two antennas on the market today for UHF utilizing circular polarization is our Helical and the Sennheiser A5000CP dome. 

A couple answers to questions or misquotes I have seen:

1. The Helical is a passive antenna, no power required. True for the A5000CP, also.

    1a. For long runs (greater than 100FT of quality cable--not RG58), you might desire a line amp.

2. You can use it for recieve or transmit applications.

3. Shure does not license or make the Helical. They stock and distribute them. But every Helical is made right here in our Orlando Floirda shop. We sell direct, as well.

If you have any questions feel free to call or write.

In the meantime, I'll settle into the lower quadrant of the pond in alligator mode.

Thanks

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Welcome, Carl, and thank you for taking the time to sign up here. I am pleased that you will be able to keep us informed from the perspective of a knowledgeable manufacturer. The more information we have and from as many sources as possible, is always a good thing.

I still have the question, and maybe you can shed some light on this, why we don't see more helical-type antennas in use in production sound recording. Is that Zaxcom, Lectrosonics, and so forth do not promote a line of antennas that incorporate helical technology? I imagine that some point Larry Fisher from Lectro may chime in here (he does read these posts I believe) and maybe we can get some answers from him.

Regards,  Jeff Wexler

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I have that question also, what would be the typical spacing between 2 helical antennas? In practice, with log periodic (shark-fin) antennas, people have been recommending all sorts of differing distances. I have made several antenna T-bars to mount 2 antennas and I have always been reluctant to adhere to one of the recommendations of 36" --- just to wide a bar to lug around. I also know that Zaxcom delivers their 2 antennas on a very narrow, maybe 12" to 16" bar, and this has always worked (though many others have claimed that this is definitely wrong).

So, with a PWS helical setup being used with a receiver diversity system like my Zaxcoms, what would be a recommended spacing?

-  Jeff Wexler

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Question,

  Why don't more people just run the units out to set and mic cable them....  No line loss and it works great...  Done it this way for  many, many, years.....

There is a time and place for the antenna situation, but day to day recording on sets, I run the tower with the stand on set.  No Problems....  Works great for me...  but to each is own...

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Question,

  Why don't more people just run the units out to set and mic cable them....  No line loss and it works great...  Done it this way for  many, many, years.....

Lots of people do it this way even today. I learned of that way first while working in New York (one of the first birthplaces of major RF Hell) where lots of sound mixers would mount their receivers on a palette and walk them close to to the talent. All the advantages of running the signal back as audio are obvious and you have none of the problems of RF signal loss on long cables, etc. That said, here are some of the reasons I know of why it is NOT done:

1. wireless work has gotten much more complex (one of the reasons why we are looking for solutions like helical antennas) often requiring many more receivers than w used to have on a palette close to the actors (typically this would have been 4 in a quad box and no more would be needed).

2. frequency searches and coordination changes would have to be done by the boom op or utility person who has access to the receivers that are now far away from the main cart the mixer is sitting behind

3. the snake required to run the audio back to the cart will have to be larger (unless you have already incorporated some sort of CAT-5 system)

4. a separate cart of some sort is needed with an appropriate powering system, etc.

I know that none of these things are problems that cannot be dealt with and the positive results of getting the receivers out close to the transmitters is well known --- I am just offering up some observations as to why this is not done more often these days

- Jeff Wexler

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Jeff,

I use no cart, but have a mini one with a spud standing by just in case....  That's nice for long nights on a backlot... Snake and all the radio mic and mic mounting gear can go on it. A nice workstation for my boom op. We sometimes put the little Honda Geni on it as well....

I use a stand with a plate and the units with  up to 5 units

Freqs are done at the beginning of the day or at each location.

Snake has 5 mic lines AND... AC. My boom op nor I mind the large snake...  If a mic line fails, it can be swapped out overnight at home..  I love this system...

Responsible Boom op meters and monitors battery usage by clock and meter on units..  No problem... and once set up, I don't need to see 'em...

Again, to each his own, but on the MANY situations where I am on the other side of a home, or outside a  small bar or location,  I run it indoors and I am done!  I prefer to stay AWAY from the filming tension,  in a nice quiet spot, whenever possible...

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BobD, nothing wrong with your way, many like RVD do it that way, as well as the Mark Ulano cat 5 method. I do it as well when I feel it has the highest chance for success. I want all the options and if the helical system is that much better for range, then I want it as well. At this point in time I am leaning towards the Ulano cat 5 method.

CrewC

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The Helical system sounds great for really long throws, like at a stadium...  They use them for Supercross and the like... they work very well from what I understand...  I seldom need such a long throw, but would like to have the option...

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Hi Carl, and thanks for the better info update!  When I began seeing your Helicals in Shure booths at trade shows, (and with Shure part numbers!) I asked, and was told that they were licensed from PWS, and I thought it curious they still had PWS markings.  When Shure began marketing Sound Devices mixers, they were specially manufactured units from SD with Shure markings, and no SD markings.  Shure also sells countryman lav mics with Shure part numbers...

apologies, also, for misspelling my old friend James' name!!

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I agree, but there is something comforting about being able to see the Rx display.

Back in my A/V days, I always ran my Rx rack backstage.

Reminds me of the film, The Untouchables. Jim Tanenebaum (mixer)- how he had to "walk the wireless recievers" on a baby plate rigged to a jr stand just off the camera frame, to get reception.

later,

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Reminds me of the film, The Untouchables. Jim Tanenebaum (mixer)- how he had to "walk the wireless recievers" on a baby plate rigged to a jr stand just off the camera frame, to get reception.

later,

All the "walk-and-talks" that were the staple in almost every Woody Allen film were done this way. Jimmy Sabat had the receivers on a palette, looked like a pancake, and this would be walked right off frame.

- JW

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  • 2 weeks later...

Here's my antenna placement practice. Let me preface it with results and circumstances vary based on constraints that may be beyond your control including but not limited to antenna cable lengths, transmit power, "the look", line of sight obstructions, space restrictions etc. For directional antennas such as Helicals or paddles I try to use the moving X pattern whenever possible. Assume a rectangle stage. One antenna is rear left corner aimed at front right corner and the other is rear right aimed at front left. Height of both is 7FT or more. The higher I can go the imaginary center of the antenna is aimed at a spot about five feet above that front corner. Aiming height will be different when mounting in truss or lighting grid. Around the center of the stage will be the intersection of the two RF pickups. Ideally, a transmitter in this spot 'X' would be picked up equally by both antennas. As you move left/right or front/back the 'X' moves. Now the pickup will favor one antenna or the other depending on the 'X' position. The antennas provide two unique "views" of the transmitter and maximizes the diversity function which is to avoid drop outs.

Helicals and the A5000CP are circular polarized antennas. As such, when you have two side by side there will be more overlap of pickup patterns than with paddle antennas which are linear polarized. Imagine two circles moving toward each other versus two vertical lines moving toward each other. In our diversity scenario, in either instance you are moving toward the same 'view' of the transmitter and defeating any advantage that diveristy offers. The antennas are not 'fighting' each other but depending on the diversity switching method of your receiver it may sound or look like a battle with the internal relay changing rapidly between the two antennas and/or the antenna A/B LEDs flashing rapidly.

If my placement width is restricted, I would still attempt whatever X pattern I could achieve. Assuming a four foot bar with antennas on each cross them to give that X in the middle of your desired pickup area. Again you take advantage of the moving X at the transmitter moves, If you aim both antennas straight ahead you will end up operating on only one antenna as the transmitter moves left or right and potentially experience a drop out.

Omni antennas - the whips on the receivers or a dipole like the Lectrosonics SNA600 - have a pickup pattern like a doughnut. Most manuals tell you to position the whips at 90 degrees to each other. Imagine those doughnuts tilted at 90 degrees. See how they are picking up different in different planes? Both straight up would have a larger intersecting area. Now not to alarm anyone with receivers that have fixed whip antennas you can't move. That's okay. These receivers can also be looking at the time or phase difference of the received signal relative to each whip. But enough higher learning for one post.

I hope I haven't confused anyone more than necessary. Any omissions are the fault of the author who is not a professor and has never played one on TV. ;)

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I wonder if a previous poster used the term "fighting each other" because he saw the lights flashing a lot, which really means that the diversity is working!

Also, Larry at Lectro did some thorough testing (discussed a while back on ramps, that found the 2 vertical whips seemed to outperform the "at right angles" placement combo

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