Modulation Dependent Carrier-Level control (MDCL) Stephen S. Lockwood, P.E. Hatfield & Dawson Consulting Engineers 9500 Greenwood, Ave, Seattle, WA [email protected] NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 1 Green Vs. Green If it is not a good financial decision I seriously question if it is a good “green” decision NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers History • Concepts date from 1930 • Renewed interest in late 1970-1980 when energy cost increased • Work done by: – British Broadcasting Corporation – Brown Boveri (BBC – ABB) – AEG-Telefunken • Systems currently implemented by: – North American Manufactures: Harris & Nautel – European Manufactures: Thomson, Transradio, Riz & Others NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 2 Energy Savings Methods • HaPuG – Harbich, Pungs & Gerth • Dependent Amplitude Modulation (DAM) • Dynamic Amplitude Carrier Modulation (DACM) • Dynamic Carrier Control (DCC) • Amplitude Modulation Companding (AMC) • Adaptive Carrier Control (ACC) • Dynamic Amplitude Modulation (DAM – again?) • Modulation Dependent Carrier-Level control (MDCL) NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers Variations on Two Methods • Reduction of carrier level during lower modulation levels – DAM, DACM, ACC • Carrier is reduced at higher levels of modulation – AMC • DCC – has been used to describe both methods • Modulation Dependent Carrier-Level control (MDCL) for the generic description NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 3 Adaptive Carrier Control (ACC) NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers Amplitude Modulation Companding (AMC) from Bell & Williams BBC NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 4 Transmitter Receiver Exciter AGC Dynamic Range Not 120 dB for AM Likely 30-40 dB Compression ~ 6 dB NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers Companding (Tomasi) System Test • Both systems had extensive listening test in Europe in the 1980s – Subjective test by the BBC on AMC - “imperceptible” to most listeners – CCIR DAM had a “theoretical impairment” on the order of 1 dB • Alaska test have not produced any listener comments or noticeable signal quality changes NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 5 Current Use in Alaska • Alaska Public Broadcasting – Chuck Lakaytis May 2008 – Funding for installation and testing – FCC Approval for Experimental Authorization – Tests on the first 2 stations showed 27% – 35% estimated savings (no separate transmitter power meter) – Installation now on 4 station with 5 this summer/fall with the rest next summer NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers Alaska Public Broadcasting 11 Very Rural AM Stations KBRW-AM KOTZ-AM KIYU-AM KNSA-AM KZPA-AM KYUK-AM KSKO-AM KDLG-AM KBBI-AM KCHU-FM KSDP-AM NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 6 Fuel and Transportation Costs: • Cost up to $ 0.50 per kWh • For 9 of 11 stations diesel fuel delivery is via barge or aircraft. • Due to shipping company fuel charges, cost have increased 40 % • Current diesel fuel price ~ $7.00/gallon, delivered. • 2010 transmitter energy bills range from $20,000 to $60,000 • No relief in site for these increases. NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers Regulatory Consideration • 47 CFR §73.1560 Operating Power and Mode Tolerance – 90% to 105% – Historically a concern about not fully serving coverage area and devices operating outside designed power range and producing spurious emissions • STA for Alaska Public Stations • FCC Public Notice DA 11-1535 authorizing use released 12 Sep 2011 – Method agnostic – Allowing “enlightened self-interest” to give operators freedom to find what is acceptable in the power savings vs. quality trade-off NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 7 NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers FCC Requirements • A letter to the FCC requesting waiver of Section 73.1560(a) • Still operate at licensed power when MDCL is disabled • Disable MDCL when asked to accommodate field strength measurements • Or you can ask for an experimental authorization should you wish NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 8 Installation • Harris has an additional circuit board that is installed in DX & 3DX transmitters from power levels of 10 kW and higher. • Nautel has an additional circuit board card or it built into an exciter replacement • Both systems relatively straight forward installation process – talk to Harris & Nautel about price – but payback it quick! NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers Compatibility with IBOC • Test from both Nautel and Harris have demonstrated that it can be used with IBOC • IBOC Carriers are lower power (-28 dBc) and remain unaffected by the analog signal • Some concern about variability in AM IBOC receivers – need some testing? NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 9 Modulation Monitors • Not required by FCC • Oscilloscope always works • Reportedly most existing units work with companding methods • Belar AMMA-2 a DPS based modulation monitor is designed to accommodate MDCL NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers Projected Cost Savings • For 50 kW transmitters: – $0.10 per kWh - k$ 19.2 per year – $0.15 per kWh - k$ 28.2 per year • For 10 kW transmitters: – $0.10 per kWh - k$ 3.9 per year – $0.15 per kWh - k$ 5.9 per year NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 10 Acknowledgments • Chuck Lakaytis – APB • Pierre Lonewolf – KOTZ, Kotzebue, Alaska • Tim Hardy – Nautel • Geoff Mendenhall & Terry Cockerill - Harris • Ann Gallagher & Susan Crawford - FCC Audio Division • Ben Dawson & Ron Rackley NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers References • Bell, C.P. and Williams, W.F.; Implementation of Amplitude Modulation Companding in the BBC MF National Networks; IEEE Transactions on Broadcasting; Vol. 35, No. 2, June 1989 • Hardy, Tim; Energy Conservation in AM Broadcast Transmitters Using Carrier Control Algorithms; Nautel; NAB Show April 2009 • Harris Corporation; Adaptive Carrier Control for DX Transmitters; Sales Brochure • Harris Corporation; Harris ACC Technical Manual 8882509002; Aug 2009 • Lakaytis, Charles; Reducing Costs at AM Transmitters Using Carrier Control Techniques; NAB Show April 2010 • Nautel, Installation and Operation Instructions, Dynamic Carrier Control PWB, NAPX05E/02 • Manson, W.I. ;Amplitude modulation radio broadcasting: application of companding techniques to the radiated signal; BBC Research Department Report No. BBC RD 1985/13., 1985 • Petke, G. and Mielke, J.; Energy Conservation and Reception Quality for Dynamic Amplitude Modulation; Institute of Radio Technology Report Number 22/80, 7 August 1980. • Rudolf, Prof. Dr.Dietmar; AM-Modulatoren; Die Technik der Amplituden-Modulatoren; RM.org; 15 Dec 2009 • Schminke, Dr. Wolfram and Boksberger, Hans-Ulrich; Dynamic Carrier Control; DCC, a Valuable Method to Save Input Power of Medium Wave Transmitters; IEEE Transactions on Broadcasting, Vol. 35, No.2, June 1989 • Schminke, Dr. Wolfram; Dynamic Carrier Control; The Merits of Modern Technology for Today’s High Power Short-Wave Transmitters; IEEE Transactions on Broadcasting, Vol. 34, No.2, June 1988 • CCIR; Report 1060, Energy Saving Methods in Amplitude Modulation Broadcast Transmitters and Their Influence on Reception Quality; Rec. 205, 1982 • Wood, James; Energy Saving for Transmitters; International Broadcasting, October 1987 • Wood, James; Megawatt Misers; International Broadcasting • Woodard, George, AM Transmitters NAB Engineering Handbook, 7th Edition, 1985 NAB Fall Radio Show 2011 Hatfield & Dawson Consulting Engineers 11.