Hi Joe and all, Thanks for making this paper available:
> Pitch-based methods for speech detection and automatic > frequency recovery > > Douglas J. Nelson and Joseph Pencak > Dept. of Defense (USA) . . > A by-product of the pitch-based detection process is a > method for automatic recovery of frequency offset of > mistuned analog speech. Mistuning is a condition > which can arise in the demodulation of single-side-band > amplitude-modulated (SSB-AM) speech if the precise > carrier is not used in the demodulation process. . . Unfortunately my efforts to use this method have failed. Step 1. A complex auto-correlation on the spectrum gives a peak at zero with phase=0 (of course) it also gives peaks symmetrically distributed around zero and these peaks correspond to the fundamental of the voice frequency. So far fine - but when this comb-like function is cross- correlated with the original spectrum to provide a curves like fig 15 in the paper, the narrow first peak does not correspond to the carrier frequency. Surely it shifts when the signal is moved within the passband. A strong signal and a wide passband allows this test. Indeed the result follows the tuning error although with a shift. But when a narrow filter is used and part of the signal is prevented from reaching the correlators, the magnitude of the shift is altered. Linrad-02.18 will have no automatic bfo setting for ssb. It does not seem to be worth the effort.... 73 Leif / SM5BSZ ############################################################# This message is sent to you because you are subscribed to the mailing list <linrad@antennspecialisten.se>. To unsubscribe, E-mail to: <[EMAIL PROTECTED]> To switch to the DIGEST mode, E-mail to <[EMAIL PROTECTED]> To switch to the INDEX mode, E-mail to <[EMAIL PROTECTED]> Send administrative queries to <[EMAIL PROTECTED]>
