Editing RWM (section)

{{Short description|Time signal radio station in Russia}}
{{Others|RWM (disambiguation)}}
{{coord|55|43|36.73|N|38|12|29.39|E|type:landmark_region:RU-MOS|display=title}}
'''RWM''' is the [[Radio call sign|callsign]] of a [[high frequency]] (shortwave) standard frequency and [[time signal]] radio station in Moscow, Russia. It is controlled by [[All-Russian Scientific Research Institute for Physical-Engineering and Radiotechnical Metrology]], and operated by [[Russian Television and Radio Broadcasting Network]]. Transmitting frequencies are 4.996&nbsp;MHz with 5&nbsp;kW and on 9.996 and 14.996&nbsp;MHz with 8&nbsp;kW.<ref>{{cite book
| author=Marten, Michael
| title=Spezialfrequenzliste 2007/08, band 2
| publisher=Siebel Verlag
| language=de
| isbn=978-3-88180-665-7
| year=2007}}</ref>

[[File:2013-03-31 1948z RWM Time Signal.ogg|thumb|A 30-second recording of RWM received at 1948 UTC on March 31st 2013 in the [[United Kingdom|UK]].]]

The frequencies are very close to those of [[WWV (radio station)|WWV]] and [[WWVH]]. Because of this, RWM is very difficult to receive in North America with simple receivers of low selectivity, due to interference from these said stations.

The mode of transmission is [[Types of radio emissions|N0N]] and [[Types of radio emissions|A1A]] (CW). Between 0 and 8 minutes past the hour, RWM transmits a straight unmodulated [[carrier wave]]. At 9 minutes past, RWM identifies itself in [[Morse code]].  Between 10 and 20 minutes past the hour, RWM transmits a pulse of carrier every second, with the difference between [[Universal Time|UT1]] and [[UTC]] in units of one-fiftieth of a second encoded onto the once-per-second pulses. Between 20 and 30 minutes past the hour, RWM transmits 10 carrier pulses each second. This transmission cycle is repeated every half-hour.<ref name="vniiftri">{{Cite FTP |url=ftp://ftp.vniiftri.ru/BULLETINS/V/bull_b16_2018.pdf|server=FTP server|url-status=dead|title=Standard Time and Frequency Signals|access-date=2018-07-15}} -- official signal specification, in russian.</ref><ref>{{Cite web |title=Recordings of the Russian Time Signal Station RWM, contains Station Identifier, 1 Hz Pulses and 10 Hz Pulses |url=https://www.youtube.com/watch?v=ZYtK5tE-v2M |access-date=2024-04-06 |website=YouTube| date=6 April 2024 }}</ref>

RWM does not transmit the time of day, only standard time intervals.

{|class="wikitable" style="text-align:center"
|+ RWM transmission schedule<ref name="betke">{{cite web |url=http://digilander.libero.it/occultazioni/segnali-di-tempo.pdf |title=Standard Frequency and Time Signal Stations On Longwave and Shortwave |access-date=2011-09-22 |last=Betke |first=Klaus |date=2007-05-19 |page=21 }}</ref>
!colspan=2| Minute || Duration || Signal
|-
| :00 || :30 || 07:55 ||align=left| Unmodulated carrier
|-
| :08 || :38 || 01:00 ||align=left| Transmitter off
|-
| :09 || :39 || 00:55 ||align=left| Morse code station identification: "RWM RWM RWM..."
|-
| :10 || :40 || 09:55 ||align=left|  1&nbsp;Hz pulses. Minute pulse 500 ms, others 100 ms, doubled with [[DUT1]] code.
|-
| :20 || :50 || 09:55 ||align=left| 10&nbsp;Hz pulses, 20 ms each. 40 ms on the second, 500 ms on the minute.
|}

The 1&nbsp;Hz pulses begin on the second, and are doubled (a second pulse transmitted from 200–300&nbsp;ms past the second) to encode [[DUT1]] and dUT1. Using these values, UT1 may be computed as:

: UT1 = UTC + DUT1 × 0.1&nbsp;s + dUT1 × 0.02&nbsp;s

DUT1 may vary between −8 and +8. The number of double pulses sent during seconds 1–8 of each minute encode positive values; if DUT1 = +5, then pulses 1 through 5 will be doubled. Doubling pulses 9–16 encodes negative values similarly.

dUT1 varies from −4 to +4.  Positive values are encoded by double pulses during seconds 21–24 of each minute.  Negative values are encoded during seconds 31–34.<ref name="betke"/>

The 10&nbsp;Hz pulses are widened in a pattern similar to that of the [[Beta (time signal)|Beta time signal]]: Most pulses are 20&nbsp;ms, but ones sent on the second are 40&nbsp;ms, and ones sent on the minute are 500&nbsp;ms.<ref name="betke"/>