JTS US-1000D and JTS US-9001D MUTE

[jts]

Hello,

I am using a wireless headphone transmitter to transmit audio to another room on 850mhz, but when I try to receive the audio using my JST US100D true diversity receiver plugged in to an amplifier via the AF out unbalanced socket there is no audio at all, the signal strength is 90% and on the JTS US-1000D screen it says mute, what exactly does mute mean and can it be turned off on the receiver? or is that option only available using JTS transmitters or similar? I also have a JTS US-9001D which also will not receive audio and says mute on the screen. Am I missing something obvious? perhaps the bandwidth the JTS is trying to receive is much wider than the transmission?

I can hear the audio fine on my SDR, (the bandwidth is 1mhz)

Thanks

[sandall]

I'm not familiar with this particular range, but I assume you mean a headset mic plugged into a belt-pack transmitter, which should have a little Mute switch on it to kill the mic but leave the transmitter switched on, which is why you are seeing a signal on your receivers (an aerobics headset, where the transmitter is built into the headband, should also have a Mute option). This is a feature on most radiomic systems & is there to allow the artist or speaker to turn themselves off without the engineer noticing (it's a recognised cause of hair-loss among audio engineers) :(. "Mute" on the receiver display could also mean that the transmitter & receiver aren't on exactly the same frequency.

 

850 MHz (in TV channel 68) is no longer legal in the UK. Do your mics have the option of switching to between 863-865MHz (channel 70), which is legal & license-free?

[bruce]

JTS radio mics use a pilot tone muting system, as do most others. The mic, when unmuted, adds a 30kHz (or thereabouts) pilot tone to the audio, which is filtered at the receiver end. If the receiver does not detect this pilot tone, it mutes the output.

 

On some receivers, you can disable this function via a menu - I know I’ve done that on Sennheiser. But I remember trying to do so on a JTS receiver, without success.

 

I think you’re saying that you’re using a random transmitter with a JTS receiver on the same frequency. If your tx isn’t adding the pilot tone, the rx will not come out of mute.

[jts]

I'm not familiar with this particular range, but I assume you mean a headset mic plugged into a belt-pack transmitter, which should have a little Mute switch on it to kill the mic but leave the transmitter switched on, which is why you are seeing a signal on your receivers (an aerobics headset, where the transmitter is built into the headband, should also have a Mute option). This is a feature on most radiomic systems & is there to allow the artist or speaker to turn themselves off without the engineer noticing (it's a recognised cause of hair-loss among audio engineers) :(. "Mute" on the receiver display could also mean that the transmitter & receiver aren't on exactly the same frequency.

 

850 MHz (in TV channel 68) is no longer legal in the UK. Do your mics have the option of switching to between 863-865MHz (channel 70), which is legal & license-free?

 

Thanks for the info Sandall, Actually its transmitting on 863.5MHz , I just rounded it off for the post. its not a mic, its a headphone transmitter which feeds audio from a radio or whatever is plugged in to it. which so happens works on the same freqs as the JTS. there is no mute option, only a switch to switch between the frequencies 863MHz and 865.MHz

 

JTS radio mics use a pilot tone muting system, as do most others. The mic, when unmuted, adds a 30kHz (or thereabouts) pilot tone to the audio, which is filtered at the receiver end. If the receiver does not detect this pilot tone, it mutes the output.

 

On some receivers, you can disable this function via a menu - I know I’ve done that on Sennheiser. But I remember trying to do so on a JTS receiver, without success.

 

I think you’re saying that you’re using a random transmitter with a JTS receiver on the same frequency. If your tx isn’t adding the pilot tone, the rx will not come out of mute.

 

Thanks for the info Bruce, Yes its a random transmitter. do you happen to know what exactly the pilot tone is? does it stay on or is the tone sent briefly to turn the mute off and again to turn it on? perhaps I could generate the tone if I knew the tone frequency, I am guessing it just sits aside the audio as a carrier? as I don't have a JTS transmitter I cant analyse the spectrum to see the tone. Would be an interesting project to create the tone to unmute the JTS.

 

Thanks

[bruce]

Don’t know the frequency offhand - it’s well above audible.

I’d be checking the various menus on the receiver to see if there is an option to disable pilot.

If not, prob easiest to look for another receiver.

 

Also, when using mismatched Tx and Rx, be aware that there will be some companding going on. A typical radio mic will apply compression to the signal, and the receiver will apply corresponding expansion. But if the tx and rx are not matched, then the compression and expansion may not match. If you search on this forum, you’ll find some discussion, including a couple of brands where the mismatching sounds quite “sweet”....

[jts]

Don't know the frequency offhand - it's well above audible.

I'd be checking the various menus on the receiver to see if there is an option to disable pilot.

If not, prob easiest to look for another receiver.

 

Also, when using mismatched Tx and Rx, be aware that there will be some companding going on. A typical radio mic will apply compression to the signal, and the receiver will apply corresponding expansion. But if the tx and rx are not matched, then the compression and expansion may not match. If you search on this forum, you'll find some discussion, including a couple of brands where the mismatching sounds quite "sweet"....

 

I figured it out, I injected a 26 KHz sign wave at the input of the transmitter using a signal generator and the mute was turned off on the JTS receiver but with a beeping noise!. I upped the tone to 52 kHz and the mute was turned off again and all was fine. :)

The sound is not fantastic though as maybe the bandwidth is not matched. or as you mention companding. Im guessing a JTS or similar transmitter has a wider bandwidth than the 1 MHz transmitter I am using. or perhaps less bandwidth, more like broadcast fm which is 200khz

Thanks for pointing me in the right direction with the tone.

[Lamplighter]

The generally used pilot tone frequency is around 32 KHz, this being a subdivision of the synthesizer used as part of the RF frequency generation process. Possibly 5 x 6.25 = 31.25 ?

Brian

[jts]

The generally used pilot tone frequency is around 32 KHz, this being a subdivision of the synthesizer used as part of the RF frequency generation process. Possibly 5 x 6.25 = 31.25 ?

Brian

 

Its interesting to note that the human ear can hear tones up to around 20 kHz but when I inject a 32kHz tone into the transmitter I can hear an audible tone on the JTS receiver along with the audio which I am feeding in, maybe the tone I can hear is a harmonic frequency. The mute is turned off with a tone added between 25 kHz and 28 kHz and again around 52 kHz give or take 3 or 4 kHz again some harmonics at work here. No audible tone is heard on the receiver at 52 kHz.

[sunray]

The generally used pilot tone frequency is around 32 KHz, this being a subdivision of the synthesizer used as part of the RF frequency generation process. Possibly 5 x 6.25 = 31.25 ?

Brian

 

Its interesting to note that the human ear can hear tones up to around 20 kHz but when I inject a 32kHz tone into the transmitter I can hear an audible tone on the JTS receiver along with the audio which I am feeding in, maybe the tone I can hear is a harmonic frequency. The mute is turned off with a tone added between 25 kHz and 28 kHz and again around 52 kHz give or take 3 or 4 kHz again some harmonics at work here. No audible tone is heard on the receiver at 52 kHz.

32KHz is also used for the return frequency on speaker alarms.

[Alec]

Blimey, talk about a load of hard work just to avoid spending the money to get a matching pair of Tx & Rx!

 

Interestingly, the user manuals for JTS kit does say "Adjustable Pilot tone squelch control can effectively reduce the noise", but this is misleading, as there's nowhere in the interface (unless it's very well hidden), so I believe it's all preset and not defeatable. Works a treat when you use the right Tx & Rx together, though.

 

Actually its transmitting on 863.5MHz , I just rounded it off for the post. its not a mic, its a headphone transmitter which feeds audio from a radio or whatever is plugged in to it. which so happens works on the same freqs as the JTS. there is no mute option, only a switch to switch between the frequencies 863MHz and 865.MHz

And, while we're at it, why on earth would you round off a frequency for posting??? Detail matters!

[jts]

Blimey, talk about a load of hard work just to avoid spending the money to get a matching pair of Tx & Rx!

 

Interestingly, the user manuals for JTS kit does say "Adjustable Pilot tone squelch control can effectively reduce the noise", but this is misleading, as there's nowhere in the interface (unless it's very well hidden), so I believe it's all preset and not defeatable. Works a treat when you use the right Tx & Rx together, though.

 

And, while we're at it, why on earth would you round off a frequency for posting??? Detail matters!

 

its nothing to do with avoiding spending money and in this case the exact freq is not relevant as I just wanted to turn off the mute which I have successfully done by introducing a tone.