STILL THE ANALOG WORLD, BUT RF MICS ARE MAKIN' ME CRAZY!

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STILL THE ANALOG WORLD, BUT RF MICS ARE MAKIN' ME CRAZY!

Postby dbbubba » Fri Mar 07, 2014 3:57 pm

I am working A2 on a large corporate show and I have eight RF mics and a four position RF com (6 channels of freqs.)
The venue is a large hotel in downtown Dallas, Texas.
I AM HAVING FITS FINDING OPEN RF CHANNELS!

I have done a frequency scan each morning and wouldn't you know it... all of the freqs.that I set up for yesterday at set up were good through rehearsals, but my main mics started getting stepped-on at show time.
For those un-familiar with how RF mics behave, they can look good on the RF meters, but if there is a transmitter within a short distance that happens to be on the same frequency things get wacky.
In this case my keynote speaker's RF lav mic started taking hits just after he walked out to do his 50 minute presentation.
The hits cause short drop outs in the signal.
There is no noise because the RF system does an automute when the signal is compromised.
Fortunately, in this case, the talent knew to move to the podium where there were two mics.
The people in the house (audience) probably never noticed the drop outs, but the video record people heard them.

In a busy metropolitan area like Dallas the available frequencies are extremely limited.
Not only are they limited, they are also crowded very close together.
Because of these two things (and other factors as well) keeping everything working gets REALLY complicated.
Suffice to say that my day is busy!

On some shows everything goes smoothly, but this is the first day of the show and all I have done is chase down RF demons. :evil:
Wish me luck and pray for my sanity!
Danny Brown
(I was going call myself Mr. B because I like people to say "MISTER" when they say my name, but then I pitied the fools.)
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Re: STILL THE ANALOG WORLD, BUT RF MICS ARE MAKIN' ME CRAZY!

Postby dbbubba » Sun Mar 09, 2014 1:47 pm

UPDATE!
At the end of the first day I re-scanned the airwaves and re-assigned all of the receiver's frequencies.
This helped to a degree, but because the show was running in the biggest hotel in Dallas and is situated right next to the Dallas Convention Center the available frequencies were limited at best (the show is over now.)
Re-assigning all of the frequencies helped, but I still had to be on my toes.

The up-side was that there were no apparent RF issues as far as anyone else knew.
I did have to be on my toes because although things were manageable, I couldn't sit back and run on cruise control. :roll:

One of the problems with a crowded RF area is the fact the eight transmitters and receivers that I was using had to be situated in a VERY narrow band.
Because of this the transmitters bleed into each other when they are close to the antennas.
There isn't enough bleed to worry about when the transmitters are on stage and away from the antennas, but when I have eight transmitters lit up and sitting ready on a table backstage it is a lot of RF in one small area.

It might seem like I could turn on the transmitters only when they are needed, but the general procedure is to fire up all of the transmitters you will be using through the course of the show and sit on the frequencies.
I generally keep all of my transmitters and mics turned on from the minute I put new batteries in the beltpacks or mics.
This is usually first thing in the morning.
This is marking your territory and one tech that I know turns on the beltpacks with mics and puts them in the rack's pull-out drawer with his tone generator blasting a 1K tone.
Not only does anyone who tries to use the frequency see RF, they are blocked with a 1K tone.

In the future I might try situating the antennas (paddles) as far away from my work table as possible.
Of course, the RF systems are only sent out with maybe 12 ft. (4 meters) of cable for the antennas.

Regardless... I am glad that show is packed-up and on trucks heading back to the warehouse!
Danny Brown
(I was going call myself Mr. B because I like people to say "MISTER" when they say my name, but then I pitied the fools.)
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Postby Dude111 » Thu Mar 13, 2014 7:45 pm

Im glad ya got things working somewhat better buddy :)
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Re: STILL THE ANALOG WORLD, BUT RF MICS ARE MAKIN' ME CRAZY!

Postby dbbubba » Tue Mar 18, 2014 4:07 pm

On the second day if the event everything ran fine because I re-assigned all of the frequencies.
Still, I am concerned with the issue of the transmitters bleeding onto one another.
I had a total of eight RF mics, 4 RF COM x-mit and 2 RF COM recieve channels.
I had no issues with the COM RF bleeding into the RF mic channels although the assigned freqs. were just as close in the band as the RF mic channels.

I need to get to the bottom of this because it is not un-common for us to have eight RF mics in use.
Even on a smaller show I will usually have four RF mics lit up.
I never know what we will need until show day and the requirements are fluid.
I try to keep all of the RF units that I have available on show days.

I'll report back if I discover anything pertinent to the issue...
Danny Brown
(I was going call myself Mr. B because I like people to say "MISTER" when they say my name, but then I pitied the fools.)
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Re: STILL THE ANALOG WORLD, BUT RF MICS ARE MAKIN' ME CRAZY!

Postby dbbubba » Wed Mar 19, 2014 12:34 pm

Well, I must have impressed the "powers that be" with the last company that handled RF for (the one I mentioned in these previous posts.)
I have been requested to travel out-of-town to handle RF (as A2) for an event.
Oh, boy! Seven days of RF fun!
The good side is that it is in San Antonio, Texas which I think is maybe a bit less crowded frequency-wise than Dallas.
However, I will again be in a convention center in a downtown area.

Since I will be working A2 I will have plenty of free time while the presenters are onstage..
I will report my experiences as they happen.
Danny Brown
(I was going call myself Mr. B because I like people to say "MISTER" when they say my name, but then I pitied the fools.)
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Re: STILL THE ANALOG WORLD, BUT RF MICS ARE MAKIN' ME CRAZY!

Postby dbbubba » Sun Mar 23, 2014 9:41 am

Thank God the RF gods are smiling down on us in San Antonio... 8-)

We have THIRTEEN channels of RF MICS and fourteen channels of RF COM... :roll:
It is also ALL working (I hate to say that because I might jinx myself.)

We actually have four channels of COM plus a few special stems for IEMs and other "private channels.)
It is a VERY complicated system to say the least.

I have to say that without the additional help of Nick Duran (A1 on event) and the rest of the Freeman Austin, Texas branch guys everything would have been a bit more of a challenge.
They made everything go quite smoothly and were a pleasure to work with.

I have four racks each with it's own COM system.
Three working and one spare (in theory, at least.)
When we set up ONLY ONE base station would work! :evil:
One unit had badly modulated audio on TRANSMIT
Another unit wouldn't power on.
The third had the BNC connector pulled off of the antenna.

After jacking-around with the unit that had bad TRNSMT audio for an hour I moved on to trying to rig the antenna wire on the unit missing the BNC.
Because it was Saturday and the BNC is an oddball type I couldn't make it work 100% and a replacement wasn't an option.
Next I moved on to opening up the unit that wouldn't power up.
Thank God I can diagnose and repair electronic equipment fairly well. :ugeek:
I re-seated a few daughter boards and the box came to life. :D
This gave us enough working channels of COM.

A GREAT IDEA GIVEN TO ME:
I did learn a VERY cool idea and possible solution to RF mics modulating between channels.
I have not had to try the idea on this show because the spectrum is much less crowded in San Antonio, so cross modulation is not an issue.
HERE'S THE IDEA:
Get a bunch of aluminum pie pans at the grocery store.
Lie each one out on your work table and put each RF BELTPACK in it's own pie pan.
The pie pan "contains" the RF (the edges of the pan do this?)
You could also put felt or something in the bottom of the pans.
Supposedly this works very well for keeping the RF from all of the transmitters from cross modulating.

I am working backstage and have to use the personal hotspot on my iPhone, so I will upload some pics of my world when I get home next week.
My backstage audio world is quite impressive.
Danny Brown
(I was going call myself Mr. B because I like people to say "MISTER" when they say my name, but then I pitied the fools.)
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