# 802.15.4 transmitted signal structure **URL:** \ **Category:** GNU Radio\ **Created:** [March 25, 2014, 10:44pm UTC](https://www.ruby-forum.com/t/802-15-4-transmitted-signal-structure/240053 "2014-03-25T22:44:47Z")\ **Posts on this page:** 4\ **Page:** 1
**Author:** ![Detlef\_R](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/d/58f4c7/32.png) [@Detlef\_R](https://www.ruby-forum.com/u/Detlef_R)\ **Post date:** [March 25, 2014, 10:44pm UTC](https://www.ruby-forum.com/t/802-15-4-transmitted-signal-structure/240053/1 "2014-03-25T22:44:47Z")
Hello GR, Is there any one who has monitored the signal generated by transceiver.py related to the 802.15.4 implementation. I want to understand the meaning its structure. I find out that it consist of a bursty transmission of a signal compound of 11 to 12 msec of wide-band signal followed by a narrower 400 Khz signal that lasts around 10 msec and is 20 db stronger then the wide-band signal. - Another unrelated point: I need to decrease at minimum the signal transmitted, if I choose the gain at transmission at 0 dB. Is there a way to even go beyond that: Does it make sense to have the “blocks.multiply\_vcc” in the transceiver.py flowgraph values between 0 and 1 ? or that have nothing to do with decreasing the magnitude of the signal transmitted ? Regards, Ruecan – View this message in context: [http://gnuradio.4.n7.nabble.com/802-15-4-transmitted-signal-structure-tp47199.html](http://gnuradio.4.n7.nabble.com/802-15-4-transmitted-signal-structure-tp47199.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![naeo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/57b2e6/32.png) [@naeo](https://www.ruby-forum.com/u/naeo)\ **Post date:** [March 26, 2014, 6:47am UTC](https://www.ruby-forum.com/t/802-15-4-transmitted-signal-structure/240053/2 "2014-03-26T06:47:20Z")
> I find out that it consist of a bursty transmission of a signal compound of > 11 to 12 msec of wide-band signal followed by a narrower 400 Khz signal that > lasts around 10 msec and is 20 db stronger then the wide-band signal. The wideband signal is the packet. Actually, it should be terminated with a tx\_eob tag. Do you see any Us on you console? AFAIK, if the packet does not end with an tx\_eob tag you might see the oscillator as narrow band signal. > - Another unrelated point: I need to decrease at minimum the signal > transmitted, if I choose the gain at transmission at 0 dB. Is there a way to > even go beyond that: > Does it make sense to have the “blocks.multiply\_vcc” in the transceiver.py > flowgraph values between 0 and 1 ? Yes, that works. Bastian ---
**Author:** ![naeo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/57b2e6/32.png) [@naeo](https://www.ruby-forum.com/u/naeo)\ **Post date:** [March 26, 2014, 3:05pm UTC](https://www.ruby-forum.com/t/802-15-4-transmitted-signal-structure/240053/3 "2014-03-26T15:05:49Z")
Hi Bastian, Bastian B.-2 wrote > The wideband signal is the packet. Actually, it should be terminated with > a tx\_eob tag. Do you see any ‘U’s on you console? AFAIK, if the packet > does not end with an tx\_eob tag you might see the oscillator as narrow > band signal. Yes I see 'U’s on the console. However I am not sure that the implementation contain such element (tx\_eob). I’ve checked the mac.cc code but did not found something referring to a tag or end of burst. May be that’s why I may see that narrow band signal. If may understanding is correct that should be fixed right and I should add such tag in the packet structure. Bastian B.-2 wrote > > Does it make sense to have the “blocks.multiply\_vcc” in the > > transceiver.py > > flowgraph values between 0 and 1 ? > > Yes, that works. But If for example I try to use 0.5 as value (blocks.multiply\_vcc(0.5)) I got this error: TypeError: in method ‘multiply\_cc\_make’, argument 1 of type ‘size\_t’ Ruecan – View this message in context: [http://gnuradio.4.n7.nabble.com/802-15-4-transmitted-signal-structure-tp47199p47223.html](http://gnuradio.4.n7.nabble.com/802-15-4-transmitted-signal-structure-tp47199p47223.html) Sent from the GnuRadio mailing list archive at [Nabble.com](http://Nabble.com). ---
**Author:** ![naeo](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/n/57b2e6/32.png) [@naeo](https://www.ruby-forum.com/u/naeo)\ **Post date:** [March 26, 2014, 3:25pm UTC](https://www.ruby-forum.com/t/802-15-4-transmitted-signal-structure/240053/4 "2014-03-26T15:25:09Z")
> May be that’s why I may see that narrow band signal. If may understanding is > correct that should be fixed right and I should add such tag in the packet > structure. You have to open the PHY block. The pdu\_to\_tagged\_stream block inserts a pdu\_length tag. Later the burst\_tagger block inserts tx\_sob and tx\_eob tags based on the pdu\_length tag. You can use the tag\_debug block to see where things go wrong. Also check the tag names in the blocks parameter. > But If for example I try to use 0.5 as value (blocks.multiply\_vcc(0.5)) I > got this error: > TypeError: in method ‘multiply\_cc\_make’, argument 1 of type ‘size\_t’ I think you want something like blocks.multiply\_const\_vcc((.5,))