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11

It depends on what you mean by "stronger". Ignoring actual limitations of your hardware and just considering the theory of communications, if you have 25 W of transmit power, then you can spread that over as much bandwidth as you want, and you're always transmitting 25 W of power. The quantity which is 25 times higher in the 100 Hz case than the 2500 Hz ...


8

The short answer is "absolutely!". :-) I started out using Digipan on Windows, but other software such as Fldigi has been released since then. Audio from the sound card to the mic input --and from the transceiver's audio out to the sound card's input-- is usually used. To prevent hum from a ground loop, it is recommended to use 600:600 ohm isolation ...


4

So, to maximize SNR you'd use a matched filter (which is the conjugate complex of the time-reversed TX pulse shaping filter), and assuming the pulse shaper has been reasonably chosen, that'd also a ISI-minimizing filter. Now, psk31.txt from the original DOS program says The solution is to filter the output, or to shape the envelope amplitude of each ...


4

This question is far too general to merit definite answers. There are free propagation prediction tools that can help you understand the possibilities. I recommend PropView, a component of the DX Lab Suite. With this tool, you can evaluate propagation paths between geographic locations based on solar weather conditions, operating mode, transmitter power, etc....


4

That was just added by someone who's primary language probably isn't English. What they meant to say is "QPSK31, a mode that is related to PSK31, uses..." Other than that, the claim "it uses more constellation points, that's a means error-correction coding", is plain wrong. The error coding used is this, just one sentence later: A ...


3

If by "strength" you mean "subjective volume as determined by a human operator", then reducing the bandwidth of the transmission while keeping the transmitter power constant does indeed produce a "stronger" signal. This is because noise is typically assumed to have a constant power spectral density over some range of frequencies of interest. Meaning, every ...


2

In this case, "allied mode" can be replace with "associated mode" or "kindred mode." The phrase indicates that there is a relationship between the two modes, BPSK and QPSK, without specifying the particulars of the relationship. "Allied mode" is not meant to convey or identify any specific technical content.


2

Transmission distance isn't limited by mode. It is limited by frequency, and sometimes power. Even given frequency and power, you can only give broad generalities on distance, because band conditions can make propagation vary in both directions by orders of magnitude. Having said that, psk31 is a narrower bandwidth than many modes, which allows power to ...


2

Yes, that's mathematically and technologically possible. Because Mike already said the latter, let me elaborate on the math side: Remember that SSB is really just AM, with one half of the transmit spectrum suppressed. Now, do the following thought experiment: You want to transmit a single RF tone at frequency 100.5 kHz. All you have is a SSB transmitter ...


2

I was not able to find very much history on these filters, but I did track down two sets of coefficients from popular implementations, and for your pleasure, I'll present them here. Transmit Filtering The pulse shape transmitted by a PSK31 transmitter is effectively a raised cosine, twice the symbol duration. That is, we can imagine a PSK31 transmitter as ...


1

Your reasoning is correct: in principle, given identical bit rate and signal power, the BER for BPSK and QPSK are identical. The Wikipedia article on PSK puts it nicely. The author there points out that you can think of a QPSK signal as two BPSK signals in the same channel, since they are orthogonal (one is built from sines, the other from cosines). You ...


1

I am sorry that I cannot provide a concrete reference but I seem to recall that it is around 80 based on some receiving software requirements.


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