Channel 69 Radio Frequencies

[howartp]

Hi,

 

Firstly I've read all the Radio Mic threads I can find on here but none of them appear to address this question/area. There are a couple with 'which frequencies will work with my existing equipment' etc.

 

We've got a UK Channel 69 Shared License, with the 14 standard frequencies. We're about to purchase around 20 AudioTechnica ATW-3110 systems together with their UHF Distribution Amp system - 10 of them will stay together, the other 10 will be distributed to churches in the area for most of the year.

 

My question is - how many of these are we likely to get working together intermod free? There's a document on Trantec's site which gives you up to sixteen channels from Channel 69 which should theoretically work together. However if you go to Audio Technica's Frequency Checker and put in even just the set of 10 frequencies, it tells you there are 10 intermod clashes. The ATW-3110's cover Channels 67-70, so I was hoping to get at least 12 frequencies working together, using Channels 69 and 70. So far with Audio Technica's checker, I've found 9 which will work from channel 69, but not together with 3 from 70. (ps - do we need a license if we went into channels 67-68?)

 

I've tried the IAS and Sennheiser applications but neither of them make any sense to me whatsoever

 

The reason I need to know is - if I can get more than 12 working together, then I need 4 UHF Distribution Amps, otherwise I only need 3. (They have 4 outputs each, plus a loop-through port for the next Amp.)

 

Oh, and yes I'm aware of all the Ofcom DSO / DDR stuff, but we're going to bite the bullet and go ahead anyway.

 

Thanks in advance for any help you can offer,

 

Peter

Network Manager by day.

A/V Technician by night.

 

Frequencies for reference: 854.900 - 855.275 - 855.900 -856.175 - 856.575 - 857.625 - 857.950 - 858.200 - 858.650 - 860.400 - 860.900 - 861.200 - 861.550 - 861.750

[Simon Lewis]

Peter,

 

The problem here is that each system has different selectivity, so the ability to squeeze the required audio quality out of the smallest slice of spectrum varies by manufacturer and individual model. Some get three systems working in channel 70, others 4.

 

If the Audio Technica intermod calculator is saying 9 from Channel 69, then chances are that's your limit - although you may achieve more by spacing the units apart. Using other manufacturer's data won't really help - their units may be netter or worse than the ATs. Why not call Audio Technica's technical support guys to check?

 

ps - do we need a license if we went into channels 67-68?

 

Yes!

 

Oh, and yes I'm aware of all the Ofcom DSO / DDR stuff, but we're going to bite the bullet and go ahead anyway.

 

Fair enough. The best outcome so far is that we get to keep Channel 69 (i.e. you won't be able to use 67-68). The worst outcome is that they take 69 as well, so you'll be able to use just three or four systems simultaneously ;-)

 

Simon

[Bobbsy]

A couple of points on why the maximum number of radio mics you can use on UHF channel 69 is a variable feast:

 

First, one thing that often seems to be forgotten here is that, when you buy a "Shared" license from JFMG, you are not buying the right to use whatever frequencies you want on the channel. You are supposed to stick to the 14 specified frequencies...and how many of these you can use depends on a number of factors.

 

For a look at these factors, it's probably worth giving a bit of simplified FM theory.

 

When you see a frequency specified for an FM radio system like RF mics, this is just the "centre frequency". Modulating the FM carrier with audio information causes the actual frequencies in use to vary above and below the centre frequency. The higher the level of the input audio signal, the farther the frequencies used move above and below the carrier frequency, up to a fixed maximum which equates to the maximum input level. This variance or frequency range is known as the FM deviation.

 

Different manufacturers use different peak deviations...for example, a Sennheiser Evo 300 system specifies a maximum deviation of 48KHz. This means that on the 854.900 frequency, when the system is working at peak level, it is transmitting on a frequency range between 854.852 MHz and 854.948 MHz. It also means that it will be generating harmonics/intermod products on this full range. Add to this the fact that the filters used to control frequencies in the transmitters and receivers can never be perfect. ETSI and the FCC specify maximum power and bandwidth but, as I said, different manufacturers use different schemes up to these maximums.

 

However, it is pretty rare to push a radio mic system to its max deviation constantly and even more rare to have every mic in a multi channel system at max deviation at the same time. This is why it is sometimes possible to use more than a theoretical maximum number of mics.

 

I know that with my old Sony mics I often used all 14 shared frequencies without ever having a problem. This was done after consultation with Sony and one of their major distributors about "real world" experience (as opposed to a spread sheet calculation).

 

...so, in effect, I've just taken all the above writing to suggest you ring the technical department at AT. They should be able to give you an accurate answer for their mics...and no info from another manufacturer is going to help you at all.

 

Bob

[dnaudio]

Quoting Bobbsy: I know that with my old Sony mics I often used all 14 shared frequencies without ever having a problem. This was done after consultation with Sony and one of their major distributors about "real world" experience (as opposed to a spread sheet calculation).

 

 

Dave Asks:

Hey Folks, I've got a set of ten Senny G2's and 3 Sony, umm err

(oh you know - the Tx beltpacks go with the Sony MB-806A reciever rack).

net net net oh yeah > WRT-805A

 

I've plotted out 14 frequencies from the Senny SIFM

(one extra for the inevitable video guy that shows up at 10 minutes to doors with a Tx that makes the lead actor go "sing sing splat buzz splat").

 

But: I can't get the Sony Tx frequencies to park on anything in the Senny SIFM list.

 

And I can't find a list of the Sony frequencies.

You pick the Sony frequencies by Channel and (Sub Channel??) eg Channel 68::03.

I can find that TV channel 68 covers half the slab of frequencies that the Senny's park within. But I can't seem to find a list of eg:

68::01 = 794-800

68::02 = 794-950

 

Does Sony have an Intermod calculator that they are hiding?

Is there a list somewhere that I haven't trawled up?

Or do I have to sit down with this rig and page through every frequency and write my own list. (the frequencies are shown on a back page, but you have to select by "channel and sub").

 

Yeah - probably I should have put the 3 Sony frequencies into SIFM and then parked the Senny's around the Sony's. - but I stupidly did it the other way and now I don't want to retune the whole rig.

 

 

All help gratefully apreciated.

 

Dave

 

As they say in co-op theatre:

"If a jobs worth doing, It's worth half doing twice."

[Dave]

Here's an old document (no longer on JFMG web site) giving some useful info - see frequency group tables at the end: http://web.archive.org/web/20030513010953/...ics/pin48_3.htm

 

The newer doc doesn't have as much detail: http://www.jfmg.co.uk/pages/Docs/Channel69IntermodFree.pdf

 

For a description of how intermodulation products are calculated, see http://en.wikipedia.org/wiki/Intermodulation

 

I'm amazed that anyone can get more than 9 channels into ch69. The ATW-3110 is not a high-end radio mic, so I'm impressed that they say 9 will be OK.

[Bobbsy]

Sorry I can't be of much specific help. When I moved to Australia I sold my old Sony mics and their manuals (which I'm sure had actual frequency lists in the back). I do recall that the legal Channel 69 frequencies for a UK Shared license were labelled something like UL1-7 and UH1-7 (for UK Lower and UK Higher). The frequencies on these corresponded to the JFMG list posted above.

 

The bad news is that, in my experience the Sony and Sennheiser mics don't "play nicely together". In the past, when I've needed to use a mixture, I've had to buy an extra license for frequencies completely separate from the Channel 69 batch.

 

As for SIFM, the problem (as you're encountering) is that it only really works if you stick to Sennheiser mics. Even if you get the Sony centre frequencies, SIFM will be assuming the same deviation, filter steepness, etc. as their mics...and Sony will be different.

 

A company that used to be good with Sony queries was TOTAL AUDIO SOLUTIONS. I used them for modifications and any maintenance I couldn't handle myself. I only say "used to" because it's six or seven years since I've had any dealings with them but they're still worth a try.

 

Bob

[TeeJay]

You may also want to try Audio Related Technology (linky - I always dealt with Simon Griffett) or even sony pro audio themselves ...

[soundo26]

Just a couple of quick points, Sony do a disk which comes with the receivers when you buy them, this has all the intermod frequencies on it! The other thing is that Total Audio Solutions are one of the companies that went into liquidation recently so Idoubt you can get much info there!

 

otherwise, most of it's been said already"

[dnaudio]

I got a student to go through and write down all the frequencies in the SONY groups.

(For the WRT Transmitter Beltpacks)

All the Best.

- Dave Newman

 

So, if you're searching threads for hard info- Here it is:

 

Sony Radio Frequencies By Group

 

A1

792.375 66.02

792.625 66.04

793.625 66.12

795.125 66.24

799.375 67.02

802.750 67.29

803.500 67.35

804.625 67.44

 

A2

799.875 67.06

801.000 67.15

801.750 67.21

803.125 67.32

804.875 67.46

805.375 67.50

 

A3

792.875 66.06

794.000 66.15

794.750 66.21

795.125 66.32

797.875 66.46

798.375 66.50

 

L1

792.250 66.01

792.500 66.03

793.250 66.09

793.875 66.14

794.375 66.18

794.750 66.21

 

L2

792.375 66.02

792.625 66.04

793.375 66.10

794.000 66.15

794.500 66.19

794.875 66.22

 

M1

796.000 66.31

796.250 66.33

797.000 66.39

797.625 66.44

798.125 66.48

798.500 66.51

 

M2

796.125 66.32

796.375 66.34

797.125 66.40

797.750 66.45

798.250 66.49

 

H1

799.500 67.03

799.750 67.05

800.500 67.11

801.125 67.16

802.375 67.26

803.500 67.35

803.875 67.38

804.375 67.42

 

H2

799.875 67.06

800.125 67.08

800.625 67.12

801.875 67.22

802.250 67.25

803.250 67.33

804.125 67.40

804.750 67.45

 

11

792.375 66.02

793.000 67.07

794.250 66.17

794.500 66.19

796.500 66.35

797.500 66.43

800.125 67.08

801.500 67.19

803.250 67.33

804.000 67.39

804.375 67.42

804.875 67.46

 

12

799.250 67.01

799.500 67.03

800.500 67.11

801.125 67.16

802.000 67.23

802.500 67.27

804.250 67.41

804.625 67.44

805.375 67.50

 

13

792.250 66.01

792.500 66.03

793.500 66.11

794.125 66.16

795.000 66.23

795.500 66.27

797.250 66.41

797.625 66.44

798.375 66.50

 

Note: Group 00 is User Defined

Starting at:

792.250 66.01

to

805.500 67.51

stepping up by 000.125

with:

799.250 67.01

 

A concurrent post has been automatically merged from this point on.

 

Oh yeah:

 

So I get the Radio rig working nicely with a couple of Sony Happy frequencies turning up to match with the Sennheiser SIFM preset frequencies and everything is hunky dory.

 

Then I turn up to work next day and there's like 5 film trucks parked outside the building. D'Oh!

 

"G'day mate, what are you shooting?"

 

"Ahh, it's just some feature."

 

"So, uh. You using any radio mics on set?"

 

"Why do you ask, Two Dogs?"

 

Turns out the venue was just a parking lot for them.

They're shooting at the far end of the campus with the theatre building as a distant background.

Ahh the school on the hill . . .

 

So all good.

 

All the best,

- Dave Newman

[Shez]

I got a student to go through and write down all the frequencies in the SONY groups.

(For the WRT Transmitter Beltpacks)

All the Best.

- Dave Newman

 

So, if you're searching threads for hard info- Here it is:

 

Sony Radio Frequencies By Group

 

A1

<snip>

 

Perhaps worth pointing out that all of those frequencies are in channels 61 and 62 - any of the Sony systems that work on ch.69 will have an entirely different set.

Still a useful reference though!