Lines Matching +full:signal +full:- +full:to +full:- +full:noise
1 <!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 4.01 Transitional//EN">
4 <meta http-equiv="content-type" content="text/html;charset=iso-8859-1">
13 <!-- #BeginDate format:En2m -->15-Nov-2012 06:42<!-- #EndDate -->
20 Autotune Port: <tt>/dev/icom</tt>; 1200/9600 baud, 8-bits, no parity<br>
23 …to one of these frequencies or, in the case of ICOM receivers, the receiver can be tuned automatic…
24 …-law companding to demodulate the data. This is the same standard as used by the telephone industr…
25 …to the broadcast time when tracking a station. However, variations up to 0.3 ms can be expected du…
26 …to the PPS signal from a GPS receiver, the mean offset with a 2.4-GHz P4 running FreeBSD…
27 … performs a number of error checks to protect against overdriven or underdriven input signal level…
28 …ctable audio codec port and signal monitoring capabilities. For a discussion of these common featu…
30 …-kHz μ-law companded codec samples using maximum-likelihood techniques which exploit the consid…
31 …-8-1, University of Delaware, August 1997, 25 pp. Available from <a href="http://www.eecis.udel.ed…
32 …to a conventional clock and the probabilities of received decimal digits. The result is a performa…
33 <h4>Baseband Signal Processing</h4>
34 …-Hz pulses and 100-Hz subcarrier are first separated using a 600-Hz bandpass filter centered on 11…
35 …-Hz subcarrier relative to the second pulse is fixed at the transmitter; however, the audio stage …
36 …signal is determined from the matched filter subcarrier envelope using a pulse-width discriminator…
37 …signal is exponentially averaged in a set of 60 accumulators, one for each second, to determine th…
38 <h4>Maximum-Likelihood Decoder</h4>
39 …to each of the valid decimal digits in this position. If any of the four bits are invalid, the cor…
40 …-likelihood digit, likelihood vector and other related data. The maximum-likelihood digit for each…
41 …-likelihood digit. If a digit likelihood exceeds the decision level and compares with previous dig…
43 …-lock loop (FLL) which operates independently of the data recovery functions. The maximum value of…
44 …to compensate for intrinsic codec clock frequency offsets up to 125 PPM. Under most conditions, th…
45 …-locked to the epoch in such a way that, when the clock state machine has reliably decoded the bro…
46 …nerable to noise and stale data, especially when coming up after a long fade. Therefore, a candida…
48 …to a fixed frequency where WWV or WWVH signals are not available throughout the day. In addition, …
49 …noise and noise alone. The driver very aggressively soaks up every scrap of signal information, bu…
50 …der bits. Only if the metric is above a defined threshold is the station signal considered accepta…
52 …is that manual synchronization via oscilloscope and HF medium is good only to a millisecond under …
53 …he sunspot cycle ending in October, 2006. Variations up to ±0.4 ms can be expected due to c…
55 …g a 2.4-GHz P4 running FreeBSD 6.1. For these measurements the computer clock was disciplined with…
56 …ter at Boulder, CO, to the receiver at Newark, DE, varies over 9.0-9.3 ms. In addition, the receiv…
58 …tations WWV and WWVH and attempts to acquire minute synch. This may take some fits and starts, as …
59 …to several minutes, depending on signal quality. When minute synch has been acquired, the driver a…
60 …to provide correct timecodes as long as the signal metric is above threshold, as described in the …
61 …to the string WV<i>f</i> for WWV and WH<i>f</i> for WWVH, where <i>f</i> is the frequency in megah…
62 …signal metric from at least one station on at least one frequency is acceptable. A consequence of …
63 …to read correctly even during the holdover interval, but with increasing dispersion. Assuming the …
65 …to automatically tune the radio in response to changing radio propagation conditions throughout th…
66 …to open the device <tt>/dev/icom</tt> and, if successful will activate the autotune function and t…
67 …to set the clock. However, during seconds 59, 0 and 1 of each minute it tunes the radio to one of …
68 …d station with the highest valid metric, ties going first to the highest frequency and then to WWV…
71 … when the ray path is in moonlight (0100-1300 UTC) and the higher frequencies when the path is in …
73 …to track the driver status is using the <tt>ntpq</tt> program and the <tt>clockvar</tt> command. T…
78 … <tt>WH</tt> for WWVH) and frequency (2, 5, 10, 15 or 20), <tt>score</tt> 32-bit shift register re…
79 <pre><tt>wwv5 000d 111 5753 3967/20.1 3523/10.2 WV20 bdeff 100 8348/30.0 WH20 0000 1 22/-12.4</tt><…
82 When enabled by the <tt>filegen</tt> facility, every received timecode is written to the <tt>clocks…
85 …re decoded from the received data and are in fixed-length format. The remaining fields are in vari…
88 …he clock is set, but turns to space when all nine digits of the timecode are correctly set and the…
90 …er is a four-bit hexadecimal code showing which alarms have been raised. Each bit is associated wi…
93 <dd>synch alarm. The decoder is not synchronized to the station within 125 μs.</dd>
99 …<dd>Compare alarm. A maximum-likelihood digit failed to agree with the current associated clock di…
101 …It is important to note that one or more of the above alarms does not necessarily indicate a clock…
103 …<dd>The timecode format itself is self explanatory. Since the driver latches the on-time epoch dir…
105 …<dd>The leap second warning is normally space, but changes to <tt>L</tt> if a leap second is to oc…
107 …ctively. The state is <tt>I</tt> or <tt>O</tt> when daylight time is about to go into effect or ou…
109 …<dd>The DUT sign and magnitude shows the current UT1 offset relative to the displayed UTC time, in…
111 … is set, this is number of minutes since the decoder was last synchronized to the station within 1…
113 …<dd>The audio gain shows the current codec gain setting in the range 0 to 255. Ordinarily, the rec…
117 <dd>The signal metric described above from 0 (no signal) to 100 (best).</dd>
119 …to determine the quality of the data signal received in the most recent minute. It is normal to dr…
121 …urrent estimate of the codec frequency offset to within 0.1 PPM. This may wander a bit over the da…
123 …<dd>The averaging time is the interval between frequency updates in powers of two to a maximum of …
127 …k was set on the last minute, the AGC is safely in the middle ot the range 0-255, and the receiver…
135 <dd>Specifies the driver stratum, in decimal from 0 to 15, with default 0.</dd>
141 …<dd>Specifies the microphone port if set to zero or the line-in port if set to one. It does not se…
143 …<dd>Enables audio monitoring of the input signal. For this purpose, the speaker volume must be set…