# GRCon15 Talk recordings **URL:** \ **Category:** GNU Radio\ **Created:** [August 29, 2015, 11:31pm UTC](https://www.ruby-forum.com/t/grcon15-talk-recordings/243180 "2015-08-29T23:31:40Z")\ **Posts on this page:** 3\ **Page:** 1
**Author:** ![Rafa\_F](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/r/958977/32.png) [@Rafa\_F](https://www.ruby-forum.com/u/Rafa_F)\ **Post date:** [August 29, 2015, 11:31pm UTC](https://www.ruby-forum.com/t/grcon15-talk-recordings/243180/1 "2015-08-29T23:31:40Z")
Hi, For anyone interested into digging into this, here are some recordings of the mic RF signal during talks at GRCon 15 [http://people.osmocom.org/~tnt/grcon/mic-f5.030000e%2B08-s2.000000e%2B06-t20150826090018.cfile](http://people.osmocom.org/~tnt/grcon/mic-f5.030000e%2b08-s2.000000e%2b06-t20150826090018.cfile) [http://people.osmocom.org/~tnt/grcon/mic-f5.030000e%2B08-s2.000000e%2B06-t20150826090030.cfile](http://people.osmocom.org/~tnt/grcon/mic-f5.030000e%2b08-s2.000000e%2b06-t20150826090030.cfile) (Hehe, I bet you didn’t expect that when you clicked on that email title :p) Microphone system is from Shure, their ULXD line of products ( [ULX-D® - Digital Wireless Systems - Shure USA](http://www.shure.com/americas/products/wireless-systems/ulxd-systems) ) FCC filing for the microphone that was used: [https://fcc.io/DD4ULXD1G50](https://fcc.io/DD4ULXD1G50) Modulation is 8-PSK and symbol rate is 156250 sym/s Cheers, ``` Sylvain ``` ---
**Author:** ![Sylvain\_M](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/839c29/32.png) [@Sylvain\_M](https://www.ruby-forum.com/u/Sylvain_M)\ **Post date:** [August 31, 2015, 12:21pm UTC](https://www.ruby-forum.com/t/grcon15-talk-recordings/243180/2 "2015-08-31T12:21:34Z")
> Message: 2 > Date: Sat, 29 Aug 2015 17:30:29 -0400 > From: Sylvain M. > To: GNURadio D.ion List [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) > Subject: [Discuss-gnuradio] GRCon15 Talk recordings > Microphone system is from Shure, their ULXD line of products ( > [ULX-D® - Digital Wireless Systems - Shure USA](http://www.shure.com/americas/products/wireless-systems/ulxd-systems) ) > FCC filing for the microphone that was used: [https://fcc.io/DD4ULXD1G50](https://fcc.io/DD4ULXD1G50) > > Modulation is 8-PSK and symbol rate is 156250 sym/s This brief may confirm a lot of what you already figured out: [http://cdn.shure.com/uploaded\_file/upload/80/Advanced\_Wireless\_Seminar\_July\_2013.pdf](http://cdn.shure.com/uploaded_file/upload/80/Advanced_Wireless_Seminar_July_2013.pdf) [http://cdn.shure.com/uploaded\_file/upload/118/2013-11-19\_Advanced\_Wireless\_Seminar\_Portland\_OR.pdf](http://cdn.shure.com/uploaded_file/upload/118/2013-11-19_Advanced_Wireless_Seminar_Portland_OR.pdf) [http://cdn.shure.com/uploaded\_file/upload/174/advanced\_wireless\_seminar\_may\_2014\_english.pdf](http://cdn.shure.com/uploaded_file/upload/174/advanced_wireless_seminar_may_2014_english.pdf) Slide 70 or 72, in particular, shows the symbol values for a Gray Coded 8-PSK constellation. 8-PSK at 156,250 symbols/sec = 1.25 Mbps. At 44.1 ksps audio, one could still fit 24-bit uncompressed audio samples in 1.25 Mbps and still keep up with some room still for overhead. I’m going to speculate whatever audio coding Shure is using, it is compressing audio to use 16 bits per sample for over the air. Also, Shure mentions in a few places that their audio codec has 2.9 ms latency. On page 26 of the PDF of this journal publication: [http://www.aes.org/journal/sample\_issue/JAES\_V50\_11\_ALL.pdf](http://www.aes.org/journal/sample_issue/JAES_V50_11_ALL.pdf) it notes that 128 samples / 44.1 ksamples/sec = 2.9025 ms. So I’m going to speculate that Shure’s audio codec operates on blocks of samples that are N\*128 samples long. That payload block size might be visible in OTA transmissions. It may be easiest to spot with audio near-silence samples that are at the end of a transmission (when the VOX decides to cut off). I have not looked at the files BTW. Regards, Andy ---
**Author:** ![Sylvain\_M](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/s/839c29/32.png) [@Sylvain\_M](https://www.ruby-forum.com/u/Sylvain_M)\ **Post date:** [September 4, 2015, 12:01am UTC](https://www.ruby-forum.com/t/grcon15-talk-recordings/243180/3 "2015-09-04T00:01:32Z")
On Sun, 2015-08-30 at 13:18 -0400, Andy W. wrote: > > Message: 2 > > Date: Sat, 29 Aug 2015 17:30:29 -0400 > > From: Sylvain M. > > Microphone system is from Shure, their ULXD line of products ( > > [ULX-D® - Digital Wireless Systems - Shure USA](http://www.shure.com/americas/products/wireless-systems/ulxd-systems) ) > > FCC filing for the microphone that was used: [https://fcc.io/DD4ULXD1G50](https://fcc.io/DD4ULXD1G50) > > > > Modulation is 8-PSK and symbol rate is 156250 sym/s FWIW, 8-PSK at 156250 sym/s confirmed. 🙂 It took me long enough. I’m so used to FSK and ASK systems, PSK took a little while to recall. -Andy