# Tx\_ofdm doubts

**URL:** <https://www.ruby-forum.com/t/tx-ofdm-doubts/234669>\
**Category:** GNU Radio\
**Created:** [March 20, 2015, 1:57pm UTC](https://www.ruby-forum.com/t/tx-ofdm-doubts/234669 "2015-03-20T13:57:07Z")\
**Posts on this page:** 1\
**Page:** 1

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**Author:** ![addis\_a](https://www.ruby-forum.com/letter_avatar_proxy/v4/letter/a/c4cdca/32.png) [@addis\_a](https://www.ruby-forum.com/u/addis_a)\
**Post date:** [March 20, 2015, 1:57pm UTC](https://www.ruby-forum.com/t/tx-ofdm-doubts/234669/1 "2015-03-20T13:57:07Z")

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hey Marcus,  
Thanks for all your help, now we are able to create our own custom block  
in  
GNU radio.  
While working on given example tx\_ofdm.grc, we have some conceptual  
doubt  
regarding chunk to symbol block…

1. Could you explain me what exactly Symbol table means and how does it  
function and also its significance, and what does payloads\_mode()  
mean…?  
2)and for packet header generator what does Formatter object mean…?

screen shot is shown in the attachment  
tx.png for 1st  
and payload\_mod.points().png for 2nd