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OK2SCS > PACKET 26.03.10 20:02l 16 Lines 642 Bytes #999 (0) @ EU
BID : 11009_OK0NMA
Read: GUEST
Subj: Re: USB or LSB on 20m?
Path: IZ3LSV<IW0QNL<OK4PEN<OK0PHL<OK0NHD<OK0NMA
Sent: 100326/1756Z @:OK0NMA.#MOR.CZE.EU #:11009 [Brno] $:11009_OK0NMA
From: OK2SCS@OK0NMA.#MOR.CZE.EU
To : PACKET@EU
HF packet is AFSK. Using USB instead of LSB means only that you
swap mark with space - same as inverting data. AX.25 uses NRZI coding
before modem (because of synchronous serial). NRZI means that 0 is
coded as signal change (1 to 0 or 0 to 1), 1 is coded as no change
(1 to 1 or 0 to 0). So what happens if we invert the NRZI? Nothing because
1 is inverted to 0, ok, but... 1 to 0 change mean 0 same as 0 to 1 change.
And no change means 1, 0 to 0 same as 1 to 1.
So using LSB is equal to USB but you have to dial diferent frequency to have
mark on the same frequency.
73 de Karel OK2SCS
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