6

Because mathematically, a function like $\sin(\omega t)$ has an angular frequency of $\omega$ and $-\omega$. Consider: $$ e^{i\omega t} + e^{-i\omega t} $$ By Euler's formula this can be expanded to: $$ \cos(\omega t)+i\sin(\omega t) + \cos(-\omega t)+i\sin(-\omega t) $$ By the trig identity $\sin(x) + \sin(-x) = 0$ this simplifies to: $$ \cos(\omega t)+ \...


5

Yes. You're looking for a transverter that will take RF from one source (your radio) and treat it as if it were an IF stage into another system. Here is an example. Obviously, you'll need to take care that you have operating privileges at the output of the transverter, including making sure spurious emissions are appropriately suppressed, etc.


4

That's just the math behind it – everything is alright with these results! You need to write down the formula of the real-valued $\sin(t)$ in terms of $e^{j2\pi t}$ and $e^{-j2\pi t}$, and you'll see that, as shown in your plots, the real-valued harmonic oscillations have a positive and a negative frequency component – so multiplying two of these yields four ...


3

Gnu Radio doesn't really know anything about frequency in cycles per second (Hz), only cycles per sample. The left of the chart is -0.5 cycles per sample, the middle is 0 cycles per sample, and the right is +0.5 cycles per sample. It's up to you to enter the correct numbers for "bandwidth" and "center frequency" if you want the scale on ...


3

This is a consequence of what was discussed in your previous question, that any real-valued function like $\sin(\omega t)$ consists of both positive and negative frequencies. Multiplying by a complex exponential $e^{i\omega t}$ simply shifts frequency by $\omega$. There are many ways to show this, one way is to simply look it up in a table of Fourier ...


1

You won't be able to, basically you'd have to redesign the whole radio. For example even if you somehow increased the frequency, there would be filters that follow that would cut down the signal. Everything is tuned and matched for a certain frequency range. There are other options but not for the Baofeng.


1

A real-valued multiply is the same as an AM modulation, where the result includes both upper and lower sidebands. (Similar to the spectrum of an AM radio station on an SDR waterfall.) A complex-valued multiply is more like an SSB modulation (plus carrier, depending on modulator depth and offset). So you only get one sideband, upper sideband if the ...


1

If I understand your question correctly, the issue is that you have one graph producing a complex output of an FFT and the other producing a floating point output from an FFT. When you produce an FFT from complex data using a floating point output, you will find that the signal is reflected across the y axis at zero. This is because the floating point ...


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