Blog Entry dated 10/25/2012 12:49 PM

This is a Function Test Post

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Remote Wireless Photoflash Switches

A Reader Asks

“I own a Nikon strobe. Can I use the same radio trigger I use on the Nikon to power my Canon strobe?”

Firstly to clarify: Radio Triggers really do not “power” anything. One cannot easily transmit power wirelessly (although Nikola Tesla would argue that fact). They are basically relays or switches that are controlled by a radio signal.

Radio controlled flash triggers are “device agnostic.” It is just an extension of your camera’s synch switch and circuitry. They have worked with most any photoflash device I have teamed them with — Canon, Nikon, Norman, Photogenic, Lumedyne, Broncolor and more. 

One thing to consider, some wireless flash triggers will serially transmit your camera’s exposure data along the  data stream in multi-lighting setups using the same flash and camera system (i.e. Nikon to Nikon, Canon to Canon) If you cross systems you will likely still be able to trigger the remote flash but it may not or will not be able to transmit the exposure data. -33-

Using Video in a Theatrical Application

A Reader Asks

“I’m debating using projections or a series of stacked televisions for an upcoming theatrical production.  I’m picturing a tower of televisions of multiple sizes on either side of the stage. The images on the televisions would be the same.  Nothing fancy like an image traveling down from the top to the bottom or one image being stretched over multiple televisions.
 
Initial thoughts: They are all daisy chained together and hooked to a single DVD or VCR.  But, how do you control them if there are periods where they wouldn’t be used?”

What you are describing is a pretty common setup. I would not recommend simply turning your video monitors on and off because some televisions will reset to a default state if they are disconnected from power and that default state might not be what you want it to wake-up in. What you need is a vertical interval video switch and a black burst generator. These devices will send black video to mute the screen when not in use. You also may want to mute the sound too. A solution for this would be a vertical interval “Audio Follow Video” switch. All “vertical interval” means is that it will switch your video seamlessly without a big break-up (glitch) on the screens.  
 
As far as interconnection, when you are sending the same source signal to all the video monitors it is seldom a good idea to “Daisy-Chain” an audio or video signal, especially when it comes from a relatively weak source device like a consumer DVD or VCR. I strongly recommend a device called a Video Distribution Amplifier. You also would need an Audio Distribution Amplifier if you are going to send the same audio to all the television monitors.  
 
I know you said you had a single source but if you wanted to send a different signal to all the monitors or do fancy images that would go from a different picture on every screen to a big blow up of a single image using all the screens there is a solution for that too. You could get software driven system that would do this automatically for you. They are expensive but rentable at a fairly reasonable cost if you are a one and done kind of user. -33-

Television Reception Calculator

Want to find out the signal reception strength of TV stations that serve your area? Check out the calculator on the FCC’s Website:

http://www.fcc.gov/mb/engineering/maps/

Enter your Zip Code or address and get the TV stations and signal strengths that can be received at your location. This takes both distance and topography into consideration and is great for procuring and aiming the correct antenna for your locale. Linked to Google Maps you can actually target your house or location using the satellite maps and dragging the teardrop to your exact area. -33-

A Disaster Plan For Television Viewing

You have Cable, Fiber or The Dish and think you are set for the new digital television cutover. Your service providers have assured you through their marketing ads that you do not have to worry about the digital transition and should just relax, sit back and enjoy the show when everyone with an antenna on their roof will be scrambling to get a signal when the government finally decides to shut down analog TV. Don’t allow yourself be lead down the primrose path because your service provider is only telling you part of the story.

 

As all services do, your television service will occasionally suffer from outages from natural and manmade disasters. Imagine for a moment that you lose your television signal but still have power or have backup power available. Imagine further that you are in need of emergency information or just want to watch your favorite show that appears on a broadcast station. What do you do when your signal from your service provider dies? The smart viewer will have a backup plan in place.

 

A backup plan consists of the following:

 

·      A “Rabbit Ear” type of TV antenna.

·      A digital to analog (DTV) converter box or a digital tuner in your television.

·      Necessary cables to make the connections between a DTV Converter and your antenna and TV.

·      Instructions on how to connect everything to your TV and scan for TV channels.

 

This may seem like a lot of trouble but you will be very happy you have your plan in place if and when you need it. You won’t be able to receive all your fancy and expensive premium channels with this setup but it is comforting to know that you will be able to receive basic broadcast television and more importantly emergency information when it is needed most. Oh, and the most important thing is not to wait for a problem before you try to make your connections and setups. Try it now when there is no stress to perform in an emergency. You will be happy you did. -33-

Digital Television Reception Simplified

Editor’s Note: This article from a broadcast engineer in Eugene, Oregon is reproduced here with permission. It does an excellent job at explaining problems about receiving digital television signals and offers some good ideas on solving the problem without technobabble.

Understanding Digital Television Reception Problems

 by Carl Sundberg – KMTR TV Engineer

 

As the acting Chief of an NBC affiliate (KMTR, Eugene, OR), I get the calls when listeners have problems making their DTV receivers and converter boxes work. Over time, most of the problems I have found were related to ATSC’s greatest weakness, Multipath.

 

Since I thought (sic) (taught) high school broadcast engineering for 28 years, I found that anyone can understand even the most complex concepts if it was put in a way they could relate. Toward that end, I have written a simple explanation of why DTV is difficult for some to receive it well and reliably. I have found that when people understand the challenge, they find ways to cope with it better and have more success.

 

Without question, it’s easier to receive the old analog TV channels than the new DTV channels. The reason is very easy to understand. If you are listening to drum beat where there is a very loud echo, you can count the beats easily as long as the beat is very slow. As the drum beats speed up, it gets harder and harder to tell if you are hearing the primary beat or the echo and at some point, that echo makes it impossible to be able to count the actual beats.

 

Analog TV had one primary signal that locked up the entire receiver. That signal pulsed at 60 times a second. The new digital signal has 8 beats that pulse at a total rate of over 19 million times a second. Because television signals can’t be heard by our ears, we don’t realize that television signals can have echoes just like sound. With an old television signal, we could see those echoes. They appeared as a secondary image that made the picture look like there were ghosts in the background of all images. Because the main signal that caused the receiver to work was at a rate of only 60 times a second, most TV receivers could lock up to that slow rate signal even when there was an echo present. Like you, listening to a slowly beating drum, the receiver could readily properly figure out what was the main beat it needed to use.

 

Since TV signals can literally bounce off of everything, signal echoes are every where. You can not eliminate them completely. Like a person listening to a drum beat where echoes can be heard, you can reduce the number of echoes by making your ears more directional by cupping the palm of your hand over your ear. If you use a funnel to listen through, you can really make your hearing very directional. We utilize this concept to make microphones more directional. Microphones used to record orchestras are usually very long tubes with the pick up element in the end of the tube.

 

Since your new digital TV or converter box is trying to receive multiple pulses that are cycling at an extremely fast rate, it gets very important for your antenna to be like the orchestra tube microphone. It needs to be pointed at the strongest signal and it needs to eliminate as much echo as possible. The traditional rabbit ear and loop antenna is a little more like a human ear. They pick up signals that come from all directions. If you use one of these devices with an amplifier, you not only amplify the signal, but the echoes as well. So, amplified antennas of this design can actually make it harder for your digital TV to work in cities where there are strong signals.

 

When the digital channels everyone is using switch to some VHF (channel 2 through 13) and some UHF, these channels will require a different type of antenna. Directional antennas will be important for the VHF channels, but they suffer less from echoes than the higher UHF channels because their wave length is longer and it takes bigger objects for their signals to bounce and make an echo.

Signals can be blocked by anything. Some objects block signals better than others. Metal objects and hills block signals very well, but you can even see a change in signal when a person walks by an antenna. For this reason, to get the best and most steady signal, an outside antenna, at least 15 feet from the ground is the best kind of antenna. By being at least 15 feet above the ground, you will be reducing echoes that come from passing cars and trucks. Another reason outside antenna’s work best is because they have more room to be larger. To make an antenna very directional, the pick up elements need proper spacing. This spacing takes length. The antennas above have many elements, but it would be even more directional if they were longer for better element spacing.

 

Don’t be surprised if an outside antenna works best when you point it in a direction away from a station. Many antenna installers will tell you they have pointed antennas at metal roof tops or water towers to get the best signal. If you have a hill in the way, sometimes you can find a metal roof top on a hilltop house that will make a good signal reflector for that hard to find, clean, echo free signal.

 

Good luck with this new technology. And always remember, echoes are what cause a signal to be difficult to receive. Very directional antennas work the best.

 

 

Article used with permission -33-

DTMF Touchtone Telephone Tones Relating to Notes on a Piano

A Reader Asks

 

“Which Piano Notes do Touch-Tone Dial Frequencies Generate?”

 

There are 8 frequencies that, when set in an X-Y Matrix combine to produce 16 dual tones. The frequencies are set in two groups. (All frequencies are in Hz).

 

High Group

 

1209

1336

1477

1633

 

Low Group

 

941

852

770

697

 

The combinations and what they create are as follows:

 

1=697+1209

2=697+1336

3=697+1477

A=697+1663

4=770+1209

5=770+1336

6=770+1477

B=770+1663

7=852+1209

8=852+1336

9=852+1477

*=941+1209

0=941+1336

#=941+1477

D=941+1663

 

SIDEBAR — The letters A, B, C and D are not commonly found on your typical telephone set. They are used for special signaling and switching operations the consumer might need with special software or home equipment.

 

Let’s use the given that A4 is 440Hz and Middle C is 256Hz. These also happen to be standard audio calibration frequencies used for certain calibrations and setups.

 

Cheating a bit an equation was not used to calculate the frequency vs. musical notes. I did a comparison against some technical information I have in my Standards and Practices tech files. This will get us in the ballpark. Most of these have a tolerance of +/- 50 cents. Here is what we discover:

 

1209 (High side of D6)

1336 (High side of E6)

1477 (Low side of F#6)

1633 (Low side of G#6)

 

941 (Low side of A#5)

852 (High side of G#5)

770 (Low side of G5)

697 (Low side of F5)

 

As you can see the frequencies do not match musical notes exactly. This is because the frequencies were chosen by design to avoid dialing mistakes by familiar ambient sounds picked-up by the telephone’s receiver (microphone). Technically, if the frequencies matched exactly, misdialing might occur if there was music playing while one was dialing. The frequencies were also chosen so as not to interfere with other telephone tones used in the network for operations like billing, call transfers and other telemetry used to advance telephone calls. -33-