Simple (I hope) question re wireless systems

Chris Harding · May 4th, 2015, 02:51 AM

Hi Paul

Absolutely ..with weddings I certainly can't afford a drop out when the bride is saying her vows!! I do also need to conceal the transmitter too and clothing does attenuate the signal ... as long as it is rock solid at 30' or less that's all I need at weddings ...the receiver is in free air but the transmitter is usually under the groom's jacket or inside his breast pocket !

Thanks Andrew .. Video Pro are my dealers anyway in Brisbane (I bought my Sony cams from them) but I didn't see anything under Rode on their website.

Chris

Jim Andrada · May 4th, 2015, 11:43 AM

Hi Paul

No, I can't leave the cable in place - have to run it for every concert. Best I could do would be to put it in the night before IF there's no event in the church. And it has to come down right after the concert.

Re the receiver size, my receiver is about 25% as big as the one in the video - it's the camera-top unit.

I'll cover it up tonight and see how it works. I'm also not going to declare a victory quite yet - will definitely give it a try at the church.

Since there's only one output jack (plus a headphone jack) I don't see any way a receiver could handle more than one stream. Now, if I could somehow figure out how to get the transmitter to pair with my PC, we might be able to do some parallel streams.

I picked up one of those little Raspberry Pi $35 linux PC's - about the size of a cigarette pack. I've been wanting to play around with programming again and I MIGHT be able to figure out how to get it to talk to the transmitter. And I think it's capable of handling several audio streams - might be a nice spare time project for the summer when it's too hot to leave the house! (We usually have our 1st 100 degree day by May 15 and June hits 110 or 112 - or more.)

Jay Massengill · May 5th, 2015, 05:59 AM

Well now I know what a Raspberry Pi is... Time to break out the credit card again.

I know this suggestion is adding one more wireless link to the chain, and wouldn't gain any redundancy since it would be in series instead of parallel, but if I had to quickly send one of these single-paired digital wireless systems to a second destination I would use one of the JM 2.4 GHz audio transmitters that I've written about to send the main receiver's headphone output to the JM 2.4 GHz receiver.

Greg Miller · May 5th, 2015, 10:58 AM

From what I've heard and read, the R-Pi does not have very good audio capabilities per se. There's a lot of code out there using the Pi as a controller, data processor, whatever, but always using a USB I/O interface for the actual A/D and D/A processing. I have not confirmed this myself, but it seems to be a widely held belief, based on a lot of internet reading on my part. YMMV.

Jim Andrada · May 5th, 2015, 12:53 PM

Hi Greg.

You're right as best I can determine. Which is why I also got an add-on sound card for the Raspberry. Takes it a bit out of the $35 range though.

Greg Miller · May 7th, 2015, 05:33 AM

It is an interesting concept. Use a $35 linux box (the RPi) to capture the data from the multi-gazillion-dollar USB sound box. Assuming the RPi is fast enough to do it without any glitches, it impresses me as a neat project.

Out of curiosity, what do you envision the RPi will do in regard to the wireless system(s)?

Jim Andrada · May 7th, 2015, 07:27 PM

Good question - FM might be doable.

The gremlin in all this is that A to D to D to A might (has to???) introduce latency above what would be there if everything worked in the Analog Domain. Everyone tends to forget that even with all our digital magic, we still live in an analog world and transitions between analog and digital don't happen in zero time..

I just need to find time to play with the RPi! A zillion years ago I used to write micro-code to drive all kinds of I/O devices - like card punches,disk drives (24 inch diameter!!!), paper tape readers, magnetic tape drives, so if I would just get off my behind and write some code I could probably figure something out.

Chris Harding · May 8th, 2015, 12:13 AM

Hi Jim

Back to the System 10, I was wondering if you have had a chance to throw a jacket over the transmitter yet to see how if affects the range???

Results would be greatly appreciated ... as long as it works to 20' that's good enough for me without any dropouts. I always have line of sight so getting a signal in another room doesn't come into the equation.

Chris

Greg Miller · May 8th, 2015, 11:05 PM

Jim,

I've still got an old Rockwell AIM65 development kit for a 6502 ... that's as far back as I go with actual programming. Before that it was all discrete TTL (CMOS gates were too fragile back then; OTOH TTL was too fast so very susceptible to noise).

If you do want to pursue broadcast band FM, let me know and we can talk about specifics. I will be out of town and probably offline completely until next Wednesday or Thursday, so hopefully you aren't in a time crunch.

John Willett · May 9th, 2015, 06:13 AM

Quote:

Originally Posted by Jim Andrada

The gremlin in all this is that A to D to D to A might (has to???) introduce latency above what would be there if everything worked in the Analog Domain. Everyone tends to forget that even with all our digital magic, we still live in an analog world and transitions between analog and digital don't happen in zero time..

Agreed - but the new Audio Limited digital 1010 system has a "through the system|" latency of just 2ms !

Jim Andrada · May 9th, 2015, 11:21 AM

Thanks John

That looks really good. I don't know anyone who would raise a fuss over 2ms.

On the other hand, I don't know what they're using for a processor. but I'd bet it's faster than the cellphone chip in the Raspberry. I wonder what an acceptable latency would be? At 29.97 one frame = 33.4ms so maybe 10 to 12ms total latency would work.

Any thoughts?

Jim Andrada · May 9th, 2015, 11:40 AM

@chris

Sorry - it slipped my mind (or what's left of it) a not so infrequent thing lately!

I'll try it today

By the way, I found the following write-up by Ty Ford - sounds like he likes it! He claims to have gotten usable signal at 200 - 250 feet.

Ty Ford Audio and Video: Audio-Technica System 10 - Now With Battery-powered Receiver & More

@Greg - according to Ty's info there's 3.8ms latency in the system 10

I really need to start playing with the Raspberry instead of just looking at it sitting forlornly on the shelf over my desk!!!!!! Even the cat seems to be ignoring it lately.

By the way, found the following re acceptable latency FWIW

https://tech.ebu.ch/docs/r/r037.pdf

Jim Andrada · May 10th, 2015, 12:31 AM

Hi Chris

As promised, I tried the AT System 10 tonight - covered the transmitter up with (well, not a coat - this is Tucson and I don't think I have one anymore) but with a very heavy 6' long bath towel wrapped around a few times - maybe 4 inches of cloth. Then I went 50 feet down the hall and into another room and recorded from the receiver. The lav mic they included was just casually tossed onto my desk near my monitors.

And it was right under my wireless access point and near the computer fans ( which you can hear clearly) which is supposedly a no-no.

Here's a link to a quick and dirty recording

https://www.dropbox.com/s/l1jpfaph45...pring.mp3?dl=0

I recorded into my Sony PCM-D50. There's a bit of noise at the start which is me walking around the office after starting a file playing (1st movement of the Beethoven "Spring" Sonata that I recorded a couple of years back performed by my wife on piano and a violinist friend.)

I didn't think it was too bad - would like to figure out how to use a better mic or pick up the output from my SD702 though instead of the lav

Anyhow, have a listen and see what you think

Chris Harding · May 10th, 2015, 03:43 AM

Hi Jim

Many thanks indeed ..I certainly didn't detect any interference or drop outs and grooms at weddings will only have a light jacket where the transmitter is dropped into so nothing like a heavy bath towel multi-wrapped

I'm impressed and it doe show that the unit can handle attenuation from clothing without any issues.

You test is greatly appreciated!

Chris

Greg Miller · May 10th, 2015, 05:03 AM

Is there really much attenuation from clothing or fabric? I would expect none.

OTOH close proximity to a human body could very well attenuate an RF signal, probably more likely at UHF than at VHF.

If the transmit antenna is in the pocket of a coat, which is hung on a plastic hanger, hanging on a rope in the middle of an open field, I would expect little or no attenuation. But the same coat, on a groom, with the antenna 1/2" from the groom's body, might be a significantly worse situation. I know from experience that making a cylinder of one's hand (as if gripping a broomstick), with a VHF antenna in the middle of the cylinder, can seriously attenuate that RF signal.

May 4th, 2015, 02:51 AM	#31
Chris Harding Inner Circle Join Date: Jul 2009 Location: Perth, Western Australia Posts: 8,441	Re: Simple (I hope) question re wireless systems Hi Paul Absolutely ..with weddings I certainly can't afford a drop out when the bride is saying her vows!! I do also need to conceal the transmitter too and clothing does attenuate the signal ... as long as it is rock solid at 30' or less that's all I need at weddings ...the receiver is in free air but the transmitter is usually under the groom's jacket or inside his breast pocket ! Thanks Andrew .. Video Pro are my dealers anyway in Brisbane (I bought my Sony cams from them) but I didn't see anything under Rode on their website. Chris

May 4th, 2015, 11:43 AM	#32
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	Re: Simple (I hope) question re wireless systems Hi Paul No, I can't leave the cable in place - have to run it for every concert. Best I could do would be to put it in the night before IF there's no event in the church. And it has to come down right after the concert. Re the receiver size, my receiver is about 25% as big as the one in the video - it's the camera-top unit. I'll cover it up tonight and see how it works. I'm also not going to declare a victory quite yet - will definitely give it a try at the church. Since there's only one output jack (plus a headphone jack) I don't see any way a receiver could handle more than one stream. Now, if I could somehow figure out how to get the transmitter to pair with my PC, we might be able to do some parallel streams. I picked up one of those little Raspberry Pi $35 linux PC's - about the size of a cigarette pack. I've been wanting to play around with programming again and I MIGHT be able to figure out how to get it to talk to the transmitter. And I think it's capable of handling several audio streams - might be a nice spare time project for the summer when it's too hot to leave the house! (We usually have our 1st 100 degree day by May 15 and June hits 110 or 112 - or more.)

May 5th, 2015, 05:59 AM	#33
Jay Massengill Trustee Join Date: Jul 2003 Location: Burlington Posts: 1,976	Re: Simple (I hope) question re wireless systems Well now I know what a Raspberry Pi is... Time to break out the credit card again. I know this suggestion is adding one more wireless link to the chain, and wouldn't gain any redundancy since it would be in series instead of parallel, but if I had to quickly send one of these single-paired digital wireless systems to a second destination I would use one of the JM 2.4 GHz audio transmitters that I've written about to send the main receiver's headphone output to the JM 2.4 GHz receiver.

May 5th, 2015, 10:58 AM	#34
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,786	Re: Simple (I hope) question re wireless systems From what I've heard and read, the R-Pi does not have very good audio capabilities per se. There's a lot of code out there using the Pi as a controller, data processor, whatever, but always using a USB I/O interface for the actual A/D and D/A processing. I have not confirmed this myself, but it seems to be a widely held belief, based on a lot of internet reading on my part. YMMV.

May 5th, 2015, 12:53 PM	#35
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	Re: Simple (I hope) question re wireless systems Hi Greg. You're right as best I can determine. Which is why I also got an add-on sound card for the Raspberry. Takes it a bit out of the $35 range though.

May 7th, 2015, 05:33 AM	#36
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,786	Re: Simple (I hope) question re wireless systems It is an interesting concept. Use a $35 linux box (the RPi) to capture the data from the multi-gazillion-dollar USB sound box. Assuming the RPi is fast enough to do it without any glitches, it impresses me as a neat project. Out of curiosity, what do you envision the RPi will do in regard to the wireless system(s)?

May 7th, 2015, 07:27 PM	#37
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	Re: Simple (I hope) question re wireless systems Good question - FM might be doable. The gremlin in all this is that A to D to D to A might (has to???) introduce latency above what would be there if everything worked in the Analog Domain. Everyone tends to forget that even with all our digital magic, we still live in an analog world and transitions between analog and digital don't happen in zero time.. I just need to find time to play with the RPi! A zillion years ago I used to write micro-code to drive all kinds of I/O devices - like card punches,disk drives (24 inch diameter!!!), paper tape readers, magnetic tape drives, so if I would just get off my behind and write some code I could probably figure something out.

May 8th, 2015, 12:13 AM	#38
Chris Harding Inner Circle Join Date: Jul 2009 Location: Perth, Western Australia Posts: 8,441	Re: Simple (I hope) question re wireless systems Hi Jim Back to the System 10, I was wondering if you have had a chance to throw a jacket over the transmitter yet to see how if affects the range??? Results would be greatly appreciated ... as long as it works to 20' that's good enough for me without any dropouts. I always have line of sight so getting a signal in another room doesn't come into the equation. Chris

May 8th, 2015, 11:05 PM	#39
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,786	Re: Simple (I hope) question re wireless systems Jim, I've still got an old Rockwell AIM65 development kit for a 6502 ... that's as far back as I go with actual programming. Before that it was all discrete TTL (CMOS gates were too fragile back then; OTOH TTL was too fast so very susceptible to noise). If you do want to pursue broadcast band FM, let me know and we can talk about specifics. I will be out of town and probably offline completely until next Wednesday or Thursday, so hopefully you aren't in a time crunch.

May 9th, 2015, 11:21 AM	#41
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	Re: Simple (I hope) question re wireless systems Thanks John That looks really good. I don't know anyone who would raise a fuss over 2ms. On the other hand, I don't know what they're using for a processor. but I'd bet it's faster than the cellphone chip in the Raspberry. I wonder what an acceptable latency would be? At 29.97 one frame = 33.4ms so maybe 10 to 12ms total latency would work. Any thoughts?

May 9th, 2015, 11:40 AM	#42
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	Re: Simple (I hope) question re wireless systems @chris Sorry - it slipped my mind (or what's left of it) a not so infrequent thing lately! I'll try it today By the way, I found the following write-up by Ty Ford - sounds like he likes it! He claims to have gotten usable signal at 200 - 250 feet. Ty Ford Audio and Video: Audio-Technica System 10 - Now With Battery-powered Receiver & More @Greg - according to Ty's info there's 3.8ms latency in the system 10 I really need to start playing with the Raspberry instead of just looking at it sitting forlornly on the shelf over my desk!!!!!! Even the cat seems to be ignoring it lately. By the way, found the following re acceptable latency FWIW https://tech.ebu.ch/docs/r/r037.pdf

May 10th, 2015, 12:31 AM	#43
Jim Andrada Inner Circle Join Date: Feb 2007 Location: Tucson AZ Posts: 2,211	Re: Simple (I hope) question re wireless systems Hi Chris As promised, I tried the AT System 10 tonight - covered the transmitter up with (well, not a coat - this is Tucson and I don't think I have one anymore) but with a very heavy 6' long bath towel wrapped around a few times - maybe 4 inches of cloth. Then I went 50 feet down the hall and into another room and recorded from the receiver. The lav mic they included was just casually tossed onto my desk near my monitors. And it was right under my wireless access point and near the computer fans ( which you can hear clearly) which is supposedly a no-no. Here's a link to a quick and dirty recording https://www.dropbox.com/s/l1jpfaph45...pring.mp3?dl=0 I recorded into my Sony PCM-D50. There's a bit of noise at the start which is me walking around the office after starting a file playing (1st movement of the Beethoven "Spring" Sonata that I recorded a couple of years back performed by my wife on piano and a violinist friend.) I didn't think it was too bad - would like to figure out how to use a better mic or pick up the output from my SD702 though instead of the lav Anyhow, have a listen and see what you think

May 10th, 2015, 03:43 AM	#44
Chris Harding Inner Circle Join Date: Jul 2009 Location: Perth, Western Australia Posts: 8,441	Re: Simple (I hope) question re wireless systems Hi Jim Many thanks indeed ..I certainly didn't detect any interference or drop outs and grooms at weddings will only have a light jacket where the transmitter is dropped into so nothing like a heavy bath towel multi-wrapped I'm impressed and it doe show that the unit can handle attenuation from clothing without any issues. You test is greatly appreciated! Chris

May 10th, 2015, 05:03 AM	#45
Greg Miller Trustee Join Date: Jan 2011 Location: Pennsylvania Posts: 1,786	Re: Simple (I hope) question re wireless systems Is there really much attenuation from clothing or fabric? I would expect none. OTOH close proximity to a human body could very well attenuate an RF signal, probably more likely at UHF than at VHF. If the transmit antenna is in the pocket of a coat, which is hung on a plastic hanger, hanging on a rope in the middle of an open field, I would expect little or no attenuation. But the same coat, on a groom, with the antenna 1/2" from the groom's body, might be a significantly worse situation. I know from experience that making a cylinder of one's hand (as if gripping a broomstick), with a VHF antenna in the middle of the cylinder, can seriously attenuate that RF signal.