Re: HF Digital Voice Modulation modes
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Gmsk is really very simple. First, it picks two frequencies that the carrier switches between. Second, the frequency is switched preciselt where the signal hits the zero voltage. Thus, it avoids the abrupt ending of one frequency waveform and start of the next. - f
As I understand it, GMSK as used by D-Star is just two tones.??
In GMSK, the transition from one tone to the other is made as soft as possible
to reduce the bandwidth of the resultant signal, the key click filter on a?
CW transmitter does something similar.
Looking around the web, I don't see much talk about D-Star modulation for HF.
My guess is that anybody using D-Star on HF just uses the same modulation scheme
as on VHF, ignoring the FCC's 300 baud max symbol rate.? ? Does anybody know for sure?
If AM phone is still legal, I suppose they would argue that a 6khz wide D-Star
transmission should be too.? Or perhaps I am wrong about the 300 baud max.
Jerry, KE7ER
On Mon, Oct 18, 2021 at 05:38 AM, Tom, wb6b wrote:
On Mon, Oct 18, 2021 at 05:18 AM, Evan Hand wrote:
I thought that FreeDV was a multiple carrier mode and would require a linear amp.
I was proposing to use the FreeDV codec but use the GMSK modulation type. Or another FSK type it it is better.?
I don't think there's any reason not to mix and match codecs (voice encoders) and modulation schemes.
Tom, wb6b
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