[hpsdr] Gnuradio 3.7 updates

[Tom McDermott]

One of the blocks, QT GUI sink is broken in the latest version of Gnuradio.
Thais breaks one of the application demo examples. A bug repost has been submitted
to gnuradio.  You can replace QT GUI Sink by QT GUI Frequency Sink to fix
the issue until gnuradio issues a bug fix.

I've created some useful utility blocks, which are in the GRC3.7 directory. They've been
tested under 3.7 but not under 3.6, so beware...

1. Static Phase shift.  This shifts complex I,Q samples by a constant amount in the
range -PI to +PI. I've used it to compensate for local oscillator phase offsets.

2. Fast Autocorrelation. This computes the autocorrelation of a signal using FFT and IFFT,
so it's much faster than convolution. No zero-padding performed, so circular wrap around
exists, but not a big deal. Helps identify periodic components in an unknown signal.

3. CWKeyboard. This takes a line of text and emits a real-valued time-domain signal at
the selected sample rate and WPM. If you Float-to-Complex this and inject into
the baseband I,Q of Hermes/Metis, it will give you CW at a zero-hertz offset from the transmit
frequency selector value.  You should low pass filter this before sending it to your
HPSDR module or you will have incredibly clicky CW (rise/fall is 1/sample_rate unless
you LPF).  Right now it does not buffer lines of text, you have to wait for the CW to finish
before hitting enter for the next line of text.  This is written entirely in Python, and shows
how to use numpy arrays to interface with gnuradio streams and make relatively fast
Python code.


-- Tom, N5EG
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