Re: [Discuss-gnuradio] Adding offset to frequency messsage?

[Tom Rondeau]

On Sat, Nov 1, 2014 at 5:43 PM, madengr <address@hidden> wrote:

I'm using the freq message output of the QT GUI Frequency Sink to drive the
freq message input of the Frequency Translating FIR Filter.  Since I have
set the the Center Frequency of the QT Frequency Sink to 7E6 Hz, that means
I need to subtract that value before I send it to the channelizer so it only
falls between -Fs/2 and +Fs/2.

I tried converting the message to float via PDU to Tagged Stream but that
does not work:

thread[thread-per-block[1]: <block pdu_to_tagged_stream (8)>]: pmt_length:
wrong_type : 7.12348e+06

Is there a proper way to do this, i.e. convert to float, add the offset, and
convert back to message?

Or is there a way to do this within the Xlating FIR Filter center frequency
field.

Thanks,
Lou
KD4HSO

No, the only way to use that feature currently would be to set your center frequency of the gui sink to 0. I suppose I could see adding another configuration option to tell the message interface to use or not use the center frequency. It'd be easy enough, but more configuration options tends to lead to more confusion. If you really want to display the RF frequency in the sink, though, this would be your only option. If you do it, feel free to send us a patch via github (with good documentation to explain the different modes) and we'll see about incorporating it.

Tom