On Sep 5, 2011, at 11:46 AM, "Marcus D. Leech" <address@hidden
> On 05/09/11 10:19 AM, John Ackermann N8UR wrote:
>> I'm generating two NBFM signals, offsetting them plus and minus 25 kHz
>> with FreqXlatingFilters, and combining the output in an adder which
>> then drives a USRP sink. It seems sensible to put a bandpass filter
>> on the result.
>> I have a basic conceptual confusion. I would think that you'd specify
>> a bandpass filter around zero with a low cutoff of, say, -40e3 and a
>> high cutoff of +40e3. However, this doesn't work -- the bandpass
>> filter seems to require a number >0 for the lowpass frequency.
> Make sure that you specify complex-taps. I assume you're using GRC. By
> default, it uses the version of
> the bandpass filter with real taps. But if you specify complex taps,
> you can use negative frequencies.
> Principal Investigator
> Shirleys Bay Radio Astronomy Consortium
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