Hello,

I am trying to implement an SSB phasing receiver using the GNU Radio
toolkit [1]. I do not have an RF frontend yet, so I had to depend on
those fortunate folks who had the required hardware to get some real
world samples. They samples are captured as given below:

50.25 mhz
cos
---- x ------- I
|
|
fc=50.30Mhz ADC -
|
|
---- x ------- Q
sin
50.25 mhz

The LSB signal which was transmitted at 50.30 mhz is digitally
downconverted with an IF of 50.25mhz. The complex samples I have is
centered at 50 khz. Now
I do exactly as described in the KK7B article on phasing receiver[2].
The I and Q signals are downconverted to baseband, and lowpass
filtered. The I channel is delayed and Q channel is passed thru hilbert
filter.

I get the audio output, when the I and Q are subtracted. Fine. But I
get audio even when they are summed together!!! i.e There is no
sideband suppression. I am wondering what the problem is. I looked at
the hilbert transformer freq response. It looks okay (allpass, with
nulls at zero and fs/2), could this null at zero cause a problem,
because the input is already at baseband?

Any advise/help will be greatly appreciated.

Thanks
Ramakrishnan

[1] htp://www.gnu.org/software/gnuradio/
[2] http://www.arrl.org/tis/info/pdf/t9301032.pdf