# Setting up a simple packet radio in 3.7.7.2 **URL:** \ **Category:** GNU Radio\ **Created:** [August 24, 2015, 9:06pm UTC](https://www.ruby-forum.com/t/setting-up-a-simple-packet-radio-in-3-7-7-2/243131 "2015-08-24T21:06:40Z")\ **Posts on this page:** 6\ **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 24, 2015, 9:06pm UTC](https://www.ruby-forum.com/t/setting-up-a-simple-packet-radio-in-3-7-7-2/243131/1 "2015-08-24T21:06:40Z")
Hello, I am trying to get a simple packet radio GRC working but so far have had no luck with the following scheme: tcp-source (port 9000) -\> packet encoder -\> gmsk mod -\> gmsk demod -\> packet decoder -\> tcp-sink (port 9001) If I remove the encoder/decoder and the gmsk mod/demod and go directly between the ports, then I am able to clearly see everything (I am using two terminals, one for tcp source and one for tcp sink). If I add back in the gmsk mod/demod I see stuff in my other terminal window (although it is garbled). Once I add the packet encoder nothing gets through again. I’ve been trying to follow some examples of this done in the past, but they were with much older versions of GNU radio and some of them used GR-extras which is no longer supported in GnuRadio 3.7. Any help would be greatly appreciated. Thanks! Priyank Patel ---
**Author:** ![PatelS\_Priyank](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/da6949/32.png) [@PatelS\_Priyank](https://www.ruby-forum.com/u/PatelS_Priyank)\ **Post date:** [August 24, 2015, 9:17pm UTC](https://www.ruby-forum.com/t/setting-up-a-simple-packet-radio-in-3-7-7-2/243131/2 "2015-08-24T21:17:47Z")
Hi Priyank, The packet decoder is checking for a preamble sequence in the data stream. If there is no output coming from the decoder the preamble is probably not being detected. How does the output of the gmsk demod look like? Also, are you transmitting the signal or are you just simulating locally? Cheers, Julian ---
**Author:** ![PatelS\_Priyank](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/da6949/32.png) [@PatelS\_Priyank](https://www.ruby-forum.com/u/PatelS_Priyank)\ **Post date:** [August 25, 2015, 11:05am UTC](https://www.ruby-forum.com/t/setting-up-a-simple-packet-radio-in-3-7-7-2/243131/3 "2015-08-25T11:05:35Z")
* * * Discuss-gnuradio mailing list removed\_email\_address@domain.invalid [https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) ---
**Author:** ![PatelS\_Priyank](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/da6949/32.png) [@PatelS\_Priyank](https://www.ruby-forum.com/u/PatelS_Priyank)\ **Post date:** [August 24, 2015, 9:48pm UTC](https://www.ruby-forum.com/t/setting-up-a-simple-packet-radio-in-3-7-7-2/243131/4 "2015-08-24T21:48:44Z")
Hi Julian, Thanks for responding so quickly! I’ve attached a picture of the current setup (if it gets through). I’ve tried looking at the output of the encoder and am seeing nothing come out of it and so there is no signal from that point on (through the gmsk mod-\>gmsk demod-\>decoder-\>tcp-sink). Is there something I need to do for the terminal messages I am sending through the tcp-source in order for the encoder block to properly process it? I am currently just simulating it locally by going directly between the gmsk-mod-\>gmsk-demod as I wanted to make sure everything goes through before I add in the USRPs. Thanks, Priyank * * * From: removed\_email\_address@domain.invalid [removed\_email\_address@domain.invalid](mailto:removed_email_address@domain.invalid) Sent: Monday, August 24, 2015 3:16 PM To: Patel, Priyank Cc: removed\_email\_address@domain.invalid Subject: Re: [Discuss-gnuradio] Setting up a simple packet radio in 3.7.7.2 Hi Priyank, The packet decoder is checking for a preamble sequence in the data stream. If there is no output coming from the decoder the preamble is probably not being detected. How does the output of the gmsk demod look like? Also, are you transmitting the signal or are you just simulating locally? Cheers, Julian Am 24.08.2015 um 21:05 schrieb Patel, Priyank \: Hello, I am trying to get a simple packet radio GRC working but so far have had no luck with the following scheme: tcp-source (port 9000) → packet encoder → gmsk mod → gmsk demod → packet decoder → tcp-sink (port 9001) If I remove the encoder/decoder and the gmsk mod/demod and go directly between the ports, then I am able to clearly see everything (I am using two terminals, one for tcp source and one for tcp sink). If I add back in the gmsk mod/demod I see stuff in my other terminal window (although it is garbled). Once I add the packet encoder nothing gets through again. I’ve been trying to follow some examples of this done in the past, but they were with much older versions of GNU radio and some of them used GR-extras which is no longer supported in GnuRadio 3.7. Any help would be greatly appreciated. Thanks! Priyank Patel ---
**Author:** ![PatelS\_Priyank](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/da6949/32.png) [@PatelS\_Priyank](https://www.ruby-forum.com/u/PatelS_Priyank)\ **Post date:** [August 25, 2015, 7:07pm UTC](https://www.ruby-forum.com/t/setting-up-a-simple-packet-radio-in-3-7-7-2/243131/5 "2015-08-25T19:07:36Z")
* * * Discuss-gnuradio mailing list removed\_email\_address@domain.invalid [https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio) ---
**Author:** ![PatelS\_Priyank](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/p/da6949/32.png) [@PatelS\_Priyank](https://www.ruby-forum.com/u/PatelS_Priyank)\ **Post date:** [August 25, 2015, 4:18pm UTC](https://www.ruby-forum.com/t/setting-up-a-simple-packet-radio-in-3-7-7-2/243131/6 "2015-08-25T16:18:45Z")
* * * Discuss-gnuradio mailing list removed\_email\_address@domain.invalid [https://lists.gnu.org/mailman/listinfo/discuss-gnuradio](https://lists.gnu.org/mailman/listinfo/discuss-gnuradio)