HFU HF Underground
Loggings => European Pirates and Private Stations => Topic started by: Ray Lalleu on October 17, 2018, 1016 UTC
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on 5780,0 in AM, also NBFM
1012 music, 1014 ID, music, 1016
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NBFM? It's not using that mode. AM only. Some receivers will detect AM in Fm mode though using slope detection, that's probably what you're hearing.
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NBFM? It's not using that mode. AM only. Some receivers will detect AM in Fm mode though using slope detection, that's probably what you're hearing.
I think that this comes from the new AM modulation systems. For example, the ampliphase use 2 carriers at full power, but modulated in phase symetrically. Then, by adding the two carriers, that should give a fixed carrier and two sidebands. But it's very difficult to make that work exactly as it should do, and any difference makes the carrier dirty. Generally, I get some bad audio in NBFM mode, but at times the audio is good (except in the fades - squelch helping about that). The audio of Zenith on 5780 is one of the best audios I can get in NBFM mode, as soon as the signal level is good. Apart of that, the signal on 5780 seems clean and specially free from any drifting.
Well, I will cease to publish NBFM results if there is nothing bad otherwise in AM listening and no splashing outside of the normal sidebands.
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Indeed, I have worked on an Ampliphase tx, they are pigs to set up but sound good when done. Its a bit of an old technique now, modern commercial TXs use PDM (or PWM) usually. No big mod transformers any more!
I think you're hearing slope detection in your rx, not fm being transmitted as such. With a PLL exciter it's highly unlikely to get any incidental FM.
A