JTS wireless mics

[Alec]

OK, to separate off from the previous general purpose topic on cheap wireless mics.

 

I'm considering buying a couple of these, one handheld and one lapel mic, in the 900 series. To save the effort of trundling long distance to see one in the flesh, I could do with a current user answering a couple of questions.

 

Are they simple to turn on and off? We will be using these in instances with no-one manning a mixer, so the talent will be turning them on and off as required. Is the on/off switch exposed, easy to use, and is it hard to do any other more sophisticated reconfiguration by mistake? Also, is the power on/off reasonably silent? I particularly ask this question as other transmitters I've seen hide the power button under a flap, which would be a pane for my situation.

 

How robust is the MH950 handheld transmitter? Is there a plasticky weak point at the base, or is it better than it looks?

 

How I wish that JTS published their manuals on their website as it would make this kind of thing much easier.

 

These will initially be freestanding, but if they serve well will be supplemented with another 2 units plus an antenna distribution amp. I may go for remote antennae - do you know what kind of cable I would need to get, and how long I could run it for (25M?) if I use the active antennae? I'm guessing I just need the best 50 ohm cable I can get, but am I being niaive?

[Simon Lewis]

Hi,

 

The perceived wisdom regarding active antennas to to avoid them like the plague...

Not only do they amplify the wanted signal, but the unwanted too - thus creating considerable problems as the receiver then has to filter out the high level unwanted signal.

 

For suitable cable to remotely mount the passive antennae see Jim Brown's rather useful treatise on Radio Mic systems.

 

Jim may come across a little strong in his views, but actually, he's absolutely correct 99.99% of the time!

 

Regarding the JTS, I've been made aware that the unit we had in the other week (brought by a covers band) could have its capsule sensitivity reduced. However, this wasn't entirely obvious, (we didn't spot it - although we were in a hurry) and the singer had no idea that this was possible.

He also had a Sennheiser system, but the shop had told him that the JTS was far superior to the Senheiser G2 300 series, which is why he bought it ;-)

 

Simon

[david.elsbury]

Are they simple to turn on and off?

 

Yep. Slide switch on the bottom of the mic.

How robust is the MH950 handheld transmitter? Is there a plasticky weak point at the base, or is it better than it looks?

Nope, it seems fairly solid to me. There's certainly no "plasticky weak point" that I'm aware of.

 

How I wish that JTS published their manuals on their website as it would make this kind of thing much easier./quote]

There's not very much in the manuals in the first place....

These will initially be freestanding, but if they serve well will be supplemented with another 2 units plus an antenna distribution amp. I may go for remote antennae - do you know what kind of cable I would need to get, and how long I could run it for (25M?) if I use the active antennae? I'm guessing I just need the best 50 ohm cable I can get, but am I being niaive?

I'm using them with 30m of RG6 (75ohm) coax in a week or so... Testing has shown that it works fine. Increases the range noticeably.

 

Do check out Jim Brown's article on wireless mics.

Oh, and Simon- they are active antennae, not passive :P

HTH

David

[Lamplighter]

Hi,

 

The perceived wisdom regarding active antennas to to avoid them like the plague...

Not only do they amplify the wanted signal, but the unwanted too - thus creating considerable problems as the receiver then has to filter out the high level unwanted signal.

 

This is not always the case. If the front end starts with a decent flter (6 section brickwall) and the following amplifier is carefully designed it is perfectly possible to use distribution amplifiers in severe conditions where even a good receiver and passive aerial will suffer interference.

 

Brian

[Simon Lewis]

This is not always the case. If the front end starts with a decent flter (6 section brickwall) and the following amplifier is carefully designed it is perfectly possible to use distribution amplifiers in severe conditions where even a good receiver and passive aerial will suffer interference.

 

 

True, but how many of these lower cost radio systems have decent selectivity? ;-)

[northernaudioman]

Hi,

 

I have no experiance of the JTS kit ( hunch would be to avoid it as the Sennheiser kit isn't that much more and works very well - but this is nothing more than a hunch! ), but active aerials.....much better to amplify the signal at the aerial than in the DA - then you amplify the signal picked up by the aerials and not the interferance aquired down the cable - especially running the sort of lengths you are talking about. We use Shure UA870 aerials with 'passive DA' and also Sennheiser ground plane aerials with Garwood ADA8 - the active Shure UA870's produce a MUCH better result and half the price.

 

The other issue is why do you need to run such long aerial cables? The loss down 25m of cable will probably cancel out any advantage of moving the aerial 25m closer! If you need to do 25m then use RG8X ( Belden ) - it's the lowest loss 50 Ohm cable I'm aware of, but it's really difficult to get hold of ( we get it from the USA ) and the BNC's can be sourced from VDC ( but they will deny all knowledge unless you speak to Doug! ). Would never recommend 75 Ohm cable ( unless you're stuck in and have to use video cable ).

 

Regards

 

Oliver.

[bruce]

[devil's advocate]

So... we have a difference of opinion. Oliver saying 50 ohm RG8X and to totally avoid 75 ohm unless you have no other option, and the Jim Brown document which says that 75 ohm cable is usually better - because it's more widely available therefore cheaper.

 

So for a given budget, you'll get a better quality 75 ohm cable than 50

 

This increase in quality by far outweighs the small loss introduced by the impedance mismatch. Specifically, if there is 10dB of loss in the cable, a 50:75 mismatch will only introduce a further 0.2dB loss.

 

 

 

Now, it's been over 20 years since I looked at RF transmission theory. And I don't have the gear to do any practical tests.

(Edit: actually, I probably could get access to it. But I don't have the inclination. Or the time. Or probably the ability.....)

 

So what's the general feeling here? What sort of cable is best?

 

[/devil's advocate]

Bruce.

 

Edit: tried to clarify a little. didn't do to well...

[electronicsuk]

If you need to do 25m then use RG8X ( Belden ) - it's the lowest loss 50 Ohm cable I'm aware of, but it's really difficult to get hold of ( we get it from the USA )

 

Both HDF400 and HDF200 have a considerably better spec than RG8X and are available at a cost of £2.12/£0.94 per metre in the UK respectively. For example, at 900Mhz RG8X has an attenuation of 12.8dB/100ft whereas HDF200 is 9.9dB and HDF400 3.9dB.

[Alec]

The other issue is why do you need to run such long aerial cables? The loss down 25m of cable will probably cancel out any advantage of moving the aerial 25m closer!

 

This is exactly the challenge I face. This would be for a permanent install so I have 2 choices:

 

1) Locate the RX kit in an equipment cupboard by the stage, with a lovely short antenna cable run. Only problem is no visibility of the displays - especially the battery level meter.

 

20 Locate the RX kit at the mix position, allowing full access to all control & display from the RX units. Not really viable to have the antennae here as it's an exposed position where it would be aesthetically difficult to position them. Only alternative is a 20-30M cable run up to the stage.

 

> Are they simple to turn on and off?

Yep. Slide switch on the bottom of the mic.

> How robust is the MH950 handheld transmitter?

Nope, it seems fairly solid to me. There's certainly no "plasticky weak point" that I'm aware of.

 

Most excellent. Can anyone with a bodypack TX confirm that it's as easy to turn on/off?

 

For suitable cable to remotely mount the passive antennae see Jim Brown's rather useful treatise on Radio Mic systems.

 

So, going to the budget possibilities, how workable would it be to use passive TV splitters such as http://www.screwfix.com/app/sfd/cat/pro.jsp?id=79447# and decent 75 ohm TV aerial cable http://www.screwfix.com/app/sfd/cat/pro.jsp?id=37838 ?

 

It's almost tempting to try this as an almost no-cost option to see if it avoids the need to purchase the expensive branded kit.

[Lamplighter]

Only alternative is a 20-30M cable run up to the stage. --

how workable would it be to use passive TV splitters such as http://www.screwfix.com/app/sfd/cat/pro.jsp?id=79447# and decent 75 ohm TV aerial cable http://www.screwfix.com/app/sfd/cat/pro.jsp?id=37838 ?

 

Alex

 

This would work though not ideal. The 4 way splitter would have a loss of approx 7.5 dB, cable loss at UHF around another 6dB and say 0.5dB for mismatch. Total 14dB. With the aerial on stage assuming a decent dipole then the extra pickup would likely balance this out. If your receivers are diversity then you should duplicate with an aerial at each side of stage.

 

Brian

[Alec]

how workable would it be to use passive TV splitters such as http://www.screwfix.com/app/sfd/cat/pro.jsp?id=79447# and decent 75 ohm TV aerial cable http://www.screwfix.com/app/sfd/cat/pro.jsp?id=37838 ?

This would work though not ideal. The 4 way splitter would have a loss of approx 7.5 dB, cable loss at UHF around another 6dB and say 0.5dB for mismatch. Total 14dB. With the aerial on stage assuming a decent dipole then the extra pickup would likely balance this out. If your receivers are diversity then you should duplicate with an aerial at each side of stage.

 

Yup, I'm aware that it's not the perfect solution, but it's still only a tenner's worth of a pair of splitters, plus I've already a bundle of decent spare TV cable - this compared with over £250 worth of dedicated splitter makes it worth having a quick go. Obviously it'd be doubled up for diversity. I figure I've got nothing to lose, if it works we're quids in, and if it doesn't I've only wasted about a tenner and go out and buy the appropriately specced branded distribution amp.

 

Thanks for the input.

[Pete Alcock]

Alec,

 

If you're seriously considering the JTS mics, price up the JTS antenna distro - you'll be surprised. It has two BNC sockets on the front and eight on the back (to feed both inputs of up to 4 receivers). It also powers all the receivers so you do away with all the crappy little power supplies. Comes with all the necessary BNC and power cables.

 

You could then use a couple of lengths of RG-whatever-it-is to feed down from your remote aerials.

 

I've said here before that the JTS stuff is very well built and performance exceeds expectation at this price point.

 

I don't know what the show is, but if it's dancey or requires a lot of sharing of the bodypack, have a look at the new JTS headset mic. Very neat and sounds amazing.

 

Pete.

 

Hi,

 

I have no experiance of the JTS kit ( hunch would be to avoid it as the Sennheiser kit isn't that much more and works very well - but this is nothing more than a hunch! ),

Thanks for that... Illuminating.

[Light Console]

I am told that JTS make Sennheiser kit anyway! They are very similar. I have recently bought a Mh-950 second hand for £200. So far I haven't got around to using it, but the sensitivity can be reduced by up to 30dB. Come to think of it, I didn't get the manual either....

I once worked with a trantec ADU (Airel Distrobution Unit) but the power supply bit packed up as soon as a reciever was plugged in! This meant I lost all mics! The only option was to source the original PSU's, which took 4 months!

[Rich]

I've said here before that the JTS stuff is very well built and performance exceeds expectation at this price point.

 

Couldn't agree more Pete. I bought a JTS kit on your recomendation and have been very satisfied with it. Extremely good value for the £200 I paid for it, I can only thank you!

 

Rich

[northernaudioman]

Hi,

 

Sorry Pete didn't mean to offend. Just an opinion.

 

Also

 

JTS do not make Sennheiser Evolution kit, it's made by Sennheiser in Germany and USA.

 

Regards

 

Oliver.