UHF vs 2.4Ghz

[Haris Pallas]

Hallo everyone,

 

I got a very simple but important question that I believe that many of you can answer just for the fun!

 

What is the band/interfierence differences between the UHF and 2.4Ghz?

 

For example => Transvideo Titan SD 2.4Ghz vs Transvideo UHF Hermes/Pegasus or Canatrans/Tandem?

 

And what about the interfierence between a 2.4Ghz wireless follow focus systems that works combined with UHF wireless video?...Is there any or not?

 

Thanks,

 

- Haris -

[Santiago Yniguez]

Hey Harris,

 

For most of the channels we use, we're in the 400-900MHz channels on UHF. 2.4 is in the GHz. So they're far apart on the wavelength spectrum.

 

 

As far as interference, in a nut shell, its all environmentally dependent. Honestly its very hard to compare the two. UHF is good for short, line of sight distances. If you know your in an environment that has "heavy microwave", UHF might be the way to go. But how are you gonna know that? There are devices that read whats floating around, but are you really gonna have that in your kit? The other day I was practicing with a friend that had a titan and I had a UHF unit. We were going the same distance and mine was rock solid. His had break up throughout the move. Not to say the Titan sucks, it doesn't. Here in the US, 2.4 is a VERY saturated frequency. On set, even more so. I believe the Titan has 4 channels to switch to. I had 30. I had places to go to, he really didn't. There are so many variables as to why one works and the other doesn't. In this case the house we were in could have had a 2.4 wireless phone or the wireless internet unit was probably on 2.4. Having higher gain antennas to switch to might have done the trick. If you want to see around corners, the UHF cannot compare. Its mostly line of sight. If I'm using UHF, I make sure my unit is on the top of rig. The least amount of obstacles between the antennas, the better.

 

You'll never get interference between UHF and a wireless follow focus thats on 2.4. My only concern would be be if you had a Bartech which lives in the 900MHz range and if your VTR guy has his own TX/RX system that is on the same. If I could afford it, I'd go with a 5.8 microwave. Its safe and legal to use in addition, not as saturated as 2.4...especially on set where it counts.

 

Hope this all helps

[Haris Pallas]

Hallo dear Santiago,

 

Thanks for all the info.It's really helpful and answers more than I expected!!

 

I have a 2.4GHz follow focus and Titan SD video link which is also 2.4GHz as you know.

 

I had an incident recently that when the FF motor was calibrated and ready to go,I switced on the Tx and the motor instantly died...I try it several times with the same resault.

We had no time to change the Tx/Rx to a different channel because we had to catch the sunset and because it was the wrap shot I just unpluged the Tx and went on with the shot without director's monitor!!..But I didn't liked that at all!!

 

Maybe if I had the time to test another channel they both could have worked.

 

Many thanks again!

 

Greetings from Greece,

 

- Haris -

[Robert Starling SOC]

Hello Haris:

 

The difference in a UHF (400 mhz +/-) signal and a 2.4 GHZ signal is the wavelength of the signal. The higher the wavelength, the more apt that signal is to be absorbed by physical and atmospheric objects. That can be something as solid as a wall or even thinner items such as foliage or even rain and humidity.

 

For instance, the lower you go in frequency, say down into the Ham Radio bands, the longer distance the signals travel and the better able they are to cut right through foliage, walls and even propagate (bounce) off the ionospheric layers of the earth. Higher frequencies do travel and in fact they can even bounce off solid objects but it is almost exclusively line of sight.

 

As an example, Ultra Low Frequency (ULF) between 300 hertz and 3 kilohertz is so capable of penetration that it is used by the military for secure communications with submarines because the antenna arrays are embedded in the bedrock of the earth and the signals penetrate bedrock and even water. Another example is 28 mhz (slightly above CB radio) is used in textile manufacturing to dry the jeans you and I wear after the fabrics are dyed or after they have been "stone washed". It's like a giant microwave tunnel but not microwaves.

 

So physically, the UHF / 400 mhz signal will be more robust and capable than a signal in the 2.4 Ghz range and a VHF 135 mhz signal better than either of the two. This is why television stations used a VHF and later UHF band of frequencies; they simply reached out and penetrated better.

 

The difference you are seeing today is the quality of the 2.4 ghz transmitter circuitry and the quality of the transmitting antenna(s). That combined with the quality of the receiver circuitry and receiver antenna(s). Old technology VHF / UHF products can or at least could get by on brute strength of a more powerful wavelength going through less dense objects. The problem is that those frequencies became over crowded with users which pushed everyone up to higher frequencies which required more sophisticated components and design.

 

While I'm not formally educated in RF, I spent many years as a competitive Ham Radio operator building large scale antenna arrays and I still hold a more than 25 year world record for the most contacts and most countries worked in a 48 hour period, including bouncing UHF signals off the trails of meteor showers from the 4th call district.

 

I hope this is somewhat helpful for you to understand the efficacy of frequency versus advanced circuitry design.

 

Robert

[Santiago Yniguez]

....What Rob said

[Haris Pallas]

Hallo Robert,

 

Many thanks to you also for the useful details!

 

I can understand the difference much clearer now..

 

Thanks guys for your time!

 

- Haris -

[William Demeritt]

While I'm not formally educated in RF, I spent many years as a competitive Ham Radio operator building large scale antenna arrays and I still hold a more than 25 year world record for the most contacts and most countries worked in a 48 hour period, including bouncing UHF signals off the trails of meteor showers from the 4th call district.

 

[Robert Starling SOC]

Careful Willy... you might be waking up with that llama one morning after NAB in Vegas with that odd taste of fur in your mouth! B)

[William Demeritt]

Careful Willy... you might be waking up with that llama one morning after NAB in Vegas with that odd taste of fur in your mouth! B)

 

Yea yea, I've stayed at the Circus Circus before...

[Ed Liew]

Can I chip in my two cents. First off need to clarify I'm no expert on this but my experience using wireless setup.

Sometime back I bought a 5.8Ghz wireless from a company in US which promise very good coverage. Result was disappointing. When I send the set for test with the local authority governing it licensing I was told it is actually operating in the analog 5.8Ghz FM range. The seller was coming out with lots of excuses when I complain and I kind of give up on getting a refund from them.

Recently I bought the BoxxTV Meridian wireless system which also operate in the 5.8Ghz range. Difference is this setup is in full digital and I can work faultless within the range of 200 meters line of sight. Down side is it cost a bomb to own one.

What I'm getting at is, most 2.4 or 5.8Ghz setup you find in the market are working in FM frequency. If the seller can't confirm if their setup is working in full digital range, do expect constant signal lost especially when working in crowded places. Also, at the end of the day it also boil do to if the investment is justifiable with the return 8)

[William Demeritt]

Can you share who the first company you had the experience with? Also, was that first transmitter an HD transmitter, or an SD transmitter operating in 5.8GHZ?

 

Sounds like the first company was transmitting using the 5.8GHZ spectrum with simple modulation (one antenna TX, one antenna RX, frequency modulation). The Titan TX transmitters advertise 2.4GHZ spectrum, but it's still an analog signal transmitted in that range. A simple television can't tune to it because they're looking for VHF and UHF; 2.4GHZ and 5.8GHZ are outside of their antenna's spectrum.

 

Boxx Meridian, IDX Camwave, Transvideo Titan HD, Switronix Recon Ultra, and others based on the AMIMON chips are different in that they broadcast a digital signal, broken into 4 pieces, using OFDM (orthogonal frequency-division multiplexing) and 4 antennas to transmit (MIMO: multiple input multiple output).

 

The antennas transmit in the 5.8GHZ range, but it's digital, not just because it's transmitted in 5.8GHZ but because the HD-SDI or HDMI signal is digitized, split up, blasted out 4 antennae, received by up to 5 antennae, mixed back together (multiplexing) to reconstitute the original signal.

 

If the first transmitter you were encountering was 5.8GHZ and simple trying to transmit the HD-SDI signal, digitally, I would imagine it would fail horribly because of the incredibly data throughput of HD-SDI. OFDM transmission works so well because it's 4 antennas broadcasting 1/4 of an HD-SDI signal with no compression, at up to 1mW on 5.8GHZ.

 

A full HD-SDI signal transmitted at 1mW over 5.8GHZ becomes INCREDIBLY susceptible to interference, and because it's a digital transmission, if you lose a part of it, you lose THE WHOLE THING (monitor turns black and says "No Input" instead of showing varying degrees of snow over a composite signal).

 

If you're looking at transmitter alternatives, and it's some company you haven't heard of, check these things out. HD, MIMO antenna, OFDM, 5.8GHZ range, etc.

[Ed Liew]

This is the first unit I've http://prairietech.us/ENG.html is a SD wireless setup. With accessories, I think I paid less than US$2,000.00. It's single antenna.

The BoxxTV Meridian is a diversity setup with four antenna on the transmitter and five on the receiver. It's SD and HD compatible. On HD, the signal is about half that of SD.