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Coming up in Silicon Chip Advertising Index AM/FM/CW Scanning HF/VHF Signal Generator Altronics...............................75-82 This low-cost, easy-to-build RF signal generator covers 100kHz to 50MHz and 70-120MHz, and is usable up to 150MHz. It generates CW (unmodulated), AM and FM test signals and also includes a scanning function for filter alignment. Ampec Technologies................. 25 Bathymetry through the ages Dr David Maddison describes how the use of knotted ropes and timber poles to measure water depth gave way to sonar. But modern sonar is about more than just water depth measurement. It can be used to map the seafloor, for discovering and imaging wrecks and other submerged objects. Blamey Saunders hears.............. 9 Control Devices........................... 7 Cypher Research Labs............... 8 Dave Thompson...................... 111 Digi-Key Electronics.................... 3 Emona..................................... IBC Rechargeable LED bicycle light Hare & Forbes....................... OBC This device uses a switchmode converter to drive a string of LEDs from a rechargeable lithium-ion battery pack. It has multiple light modes and automatically reduces the LED current to prevent overheating. Jaycar............................ IFC,53-60 Speed-based Volume Control Newer vehicles can automatically increase the radio/audio playback volume as you accelerate, to help overcome increased road, engine and wind noise. Now you can add this feature to just about any vehicle with this unit. It senses your speed using a GPS receiver and adjusts the audio signal volume accordingly. Keith Rippon Kit Assembly...... 111 LD Electronics......................... 111 LEACH Co Ltd........................... 65 LEDsales................................. 111 Microchip Technology................ 29 Mouser Electronics...................... 5 12V Battery Isolator Ocean Controls......................... 11 This solid-state device automatically connects an auxiliary battery for charging when the vehicle alternator is running. It can handle charge currents in excess of 100A, does not get hot during operation, produces little to no EMI and has a low current drain when off. PCBcart................................... 19 PCB Designs........................... 111 SC Majestic Loudspeaker......... 73 Silicon Chip Shop.................. 109 Note: these features are planned or are in preparation and should appear within the next few issues of Silicon Chip. The Loudspeaker Kit.com......... 10 The June 2019 issue is due on sale in newsagents by Thursday, May 30th. Expect postal delivery of subscription copies in Australia between May 28th and June 14th. Vintage Radio Repairs............ 111 Tronixlabs................................ 111 Wagner Electronics................... 99 Notes & Errata Multi Diode Curve Plotter, March 2019: in Fig.2 on page 67, the resistor to the left of and slightly above diode D1 (in the middle of a group of three labelled 10kW) should be labelled 1kW. The circuit diagram and silkscreen on the PCBs sold in our Online Shop is correct. DAB+/FM/AM Radio, January-March 2019: the PCBs we have supplied for this project are marked RevC, but they are actually RevD boards, with the extra resistors as described in the article. They were simply mislabelled. No RevC boards have been sent to customers. 3-Way Adjustable Active Stereo Crossover, September-October 2017: there is a mistake in the PCB design which means that if a transformer with a centre-tapped secondary (or two secondaries connected in series) is used, those secondaries are shorted out when the unit is switched off. To solve this, cut the top layer copper rectangle joining the two front-most power switch terminals between the two pins, or use a RevE PCB, which no longer has these two pins shorted together. The additional feature I would like to incorporate is for the entertainment channel to be muted when there is activity on the marine channel. Do you have any suggestions on the best way to do this? (G. C., Mount Dandenong, Vic) • You can use a VOX (Voice-Operated 112 Silicon Chip Switch/Relay) to do this. The latest one that we published was in the July 2011 issue of Silicon Chip (siliconchip.com. au/Article/1101). Feed the marine VHF channel audio signal to the VOX input and wire up the entertainment channel to the mixer input via one of the NC/ COM relay pairs on the VOX board. Australia’s electronics magazine That way, when the VOX board detects activity on the marine channel, the entertainment channel will be automatically disconnected. It will be re-connected after some period of inactivity on the marine channel, as determined by the delay setting on the VOX (VR2). SC siliconchip.com.au