16 UHF Radio Mics in Ch. 69 ?

[jradley]

Hi,

 

I'm afraid this is yet another UHF radio mic question, but one I couldn't find an answer for from searching usual resources including here.

 

I'm looking to use 16 UHF radio mics for a production I am working on. The mics I have available are an eclectic mix of Sennheiser evolution, with 10 100's, 2 100 G2's and 4 300 G2's.

 

I have a license for the channel 69 shared frequencies and am well aware of the standard 14 frequencies available. However, on the Trantec website they list a possible 16 frequencies in channel 69, the usual 14 plus 858.975 and 859.500. Has anyone tried these sucessfully to build a set of 16 in total ?

 

If I am stuck with just 14 in ch.69, is there any preferred frequencies (or ones to avoid particularly) from the license free ch.70 set, or is it all just too hit and miss to predict ?

 

In testing yesterday I had all the 100's running in Ch. 69 and the 4 300's running in Ch. 70 and although it all started out ok there were problems later on in the evening with one of the ch. 70 mics, which didn't entirely surprise me. Am I pushing the boundaries of luck somewhat ?

 

Cheers,

 

John

[Shez]

I believe Sennheiser themselves are very helpful at sorting out these things & if you give them a call, they'll explain exactly what is & isn't possible with their kit.

 

It varies between manufacturers so a channel plan for Trantec may not work for Sennheiser & vice versa. I suspect you'll struggle to do this without additional expenditure though. I don't think the Evos will work on more than 8 of the ch.69 frequencies simultaneously without intermod products becoming problematic.

[jradley]

I've had no problems at all in the past running 10 evo 100's. Unfortunately when I have spoken to Sennheiser in the past I'm sorry to say my experience has not been too good - they have generally advised me to buy evo 300s or 500s (for receiver/frequency issues) or MKE2 gold capsules (for capsule issues).

 

John

[Shez]

I've had no problems at all in the past running 10 evo 100's. Unfortunately when I have spoken to Sennheiser in the past I'm sorry to say my experience has not been too good - they have generally advised me to buy evo 300s or 500s (for receiver/frequency issues) or MKE2 gold capsules (for capsule issues).

 

I guess it depends on your expectations for the kit and the level at which you work. If you're happy with the bundled capsules, then fine. The MKE2s are commonly used in pro circles because they sound decent, are small and are reasonably tough. The (bundled) ME2s aren't used in these circumstances because they don't meet the criteria for pro users.

 

Same with frequencies - you can use more than they recommend. If the resulting intermod distortion isn't a problem for you (or even audible in the circumstances that you're using them), then go for it!

 

I think the best answer I can give is that if you can arrange a frequency plan for the frequencies that you have available that works for you, then use it. The professional advice would be to use a frequency plan that the manufacturer recommends; if it means more kit, then more kit is needed.

 

I assume this is for an amateur production?

 

Can you cut down the number of channels needed by swapping packs?

[Graham Threader]

Sennheiser recommend running a maximum of 8ways in a TV Channel ie ch69. More than this pushing your luck.

 

The SK50/1046 range is generally rated for 12 channels without much difficulty. Trantec say they can get more channels - and I think they can - but there is far more involved that just frequencies. For example, the maximum deviation also affects this issue. As a rough guide, the greater the deviation, the greater the data transfer, the higher the quality. Thus if you reduce deviation you can often squeeze in more channels, while the theroretical loss of quality may not be obvious.

 

If you contact JFMG it is often possible to Licence extra TV channels for your use. This will ease you intermod problems.

 

Remember that conditions change with an audience present, and if you are 'on the edge' at rehearsal, you may find it falls apart in performance.

[StevieR]

I'll try to answer this as concisely as possible but will probably waffle at some point...

 

Firstly, legally there are only fourteen frequencies that can be used in channel 69 under a shared microphone license. There are other frequencies in this band but you will require a separate fixed site license to use these.

 

Secondly, the evolution series supports up to 8 frequencies per channel without risk of intermodulation problems. It is possible to sometimes squeeze in an extra two to get ten but after that your going to start getting problems. To get the full 14, you are going to need to move up to the 3000 or 5000 series to get that density of frequencies.

 

Steve

[jradley]

Many thanks for all the replies.

 

It looks like my best bet will be to get a 48 hour site license for say 4 or 6 of the mics, which should take the pressure off ch69 and ch70.

 

I assume as I'm already a license holder JFMG can do that with a couple of days notice ?

 

Cheers,

 

John

[Shez]

I assume as I'm already a license holder JFMG can do that with a couple of days notice ?

 

I think they can do it at short notice but there may be an additional charge to rush it through. Give them a bell.

 

Shez

[Solstace]

Wow!

 

I've seen 12 Evolution G2 500's and 1 Evolution 300 (previous generation) run together on channel 69 before now, without coming across serious intermod problems. Admittedly this was for an amateur show, but still!!

 

C.

[J Pearce]

I recently worked on a production that had 29 channels of UHF radios.

The answer really is to go to someone who knows what they are doing and say this is what I want, how much?

 

Our whole sound rig was provided by Delta, and they sorted out licenses, frequencies and what radios to use. We had 15 Trantec S5000s and 15 Sennheiser somethings.

 

I don't know what bands we were running in, I was FOH and on lighting, so didn't really see the radios.

[Shez]

I've seen 12 Evolution G2 500's and 1 Evolution 300 (previous generation) run together on channel 69 before now, without coming across serious intermod problems. Admittedly this was for an amateur show, but still!!

 

Can anyone describe exactly what intermod distortion sounds like? I know that's not an easy question, but I'm beginning to wonder how much of an issue it is. Quite a few people have posted stories of success using more channels than the manufacturers recommend; presumably any problems have been sufficiently inaudible for those people that it's not been an issue.

 

I know that in the pro world, ears are much keener, speaker systems are more revealing, occasional fizzes are totally unacceptable etc, so problems may be more apparent than in a typical amateur show. Even so, I'd be interested to know just how much of a problem it is.

[Chappie]

I recently worked on a production that had 29 channels of UHF radios.

The new Lord Of The Rings show in Toronto uses 155. What a nightmare.

[northernaudioman]

Hi,

 

I regularly use the standard set of 14 JFMG ch: 69 frequencies on Evolution G2 500 Series without any problems....for more frequencies you can also get away with using the de-regulated frequencies to get to 18 channels at a push. They are used with directional aerials to minimise some external RF.

 

Sennheiser say that there is no difference between the 100/300/500 G2 series in terms of RF performance - it's functionality that is reduced on the cheaper series. I' not sure how much difference there is between the G1 & G2 series.

 

Try running the system up keeping the transmitters apart from each other ( a foot or so ) to avoid too much harmonic interaction and see if you can hear any odd twittering / interferance, and also try to keep any spare / unused packs off when you can during the show ( don't put them on the radio rack when they are not in use! ) to minimise excess RF.

 

Hope this helps.

 

Oliver.

[gingertom]

Maybe I've been mis-informed... but everytime I've no2'ed or run radios (and the way I was taught) was to always keep reduntant packs on, to maintain the same amount of "traffic". I've certainly had 12/14/16 way SK50 sets that have gone belly up when turns have powered their Tx's down.

[Shez]

It's a cardinal rule for me that once the packs go on at the start of the show, they never go off until the end. At some point, someone will forget to switch one back on again, and once they're on stage, there's nothing you can do about it. Been there, slapped the actors about afterwards.

 

I've even had a performer have a go at me because he switched off his own pack after soundcheck (against my instructions) and forgot to switch it back on (I didn't have a no. 2 during that show). The SM managed to make him aware of this whilst he was on stage, and he insisted that he did switch it on "6 times" whilst on stage... It was a Sony freedom with the timer that clocks how long it's been switched on so I checked after the show; a total of 5 minutes after his 20 minute spot. Coincidentally, the soundcheck lasted about 5 minutes...

 

In summary, DON'T SWITCH THEM OFF! EVER!

 

(Yes, you have touched a sore point here :( )