GNU Radio is one of those love it and hate it applications. I like how I
can plug in my Pluto learning module and transmit and receive waveforms. Or
my old RTL dongle. It's just amazing.
What I wanted actually is a Quadrature modulator. There's a Quadrature
demodulator, so why not the opposite? No problem, I'm sure someone in the
last 10 years has some code to implement one. Well a google search found
none, but I got side tracked and bought 25 picks and a new strap for my
guitar...
So I coded up a 3200 codec with the default OFDM modulator, and looked at
it using the RTL dongle and gqrx. Here's a link to the waveforms:
Waveform Examples <https://goo.gl/izAZmV>
My 3200 codec is transmitting 1.56 MHz wide. Golly! (433.190 to 434.750).
This is no good. It's a worthless GNU Radio option. I only want to transmit
one sideband.
I read in David's blog where he's not a big fan of IQ Modulators, and I
guess no one else is either. "but I persisted". I happened across the
LTC5599 chip. It's $10 in single quantities, so I guess they aren't selling
a lot of them. It's neat though how you can program its registers and get
the waveform optimized. A little bit more filtering, a 12 watt brick, and
you're ready to go with 1.25 Khz spaced voice channels on VHF.
73
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