---------------------------------------------------------- AeroElectric-List Digest Archive --- Total Messages Posted Thu 10/18/12: 2 ---------------------------------------------------------- Today's Message Index: ---------------------- 1. 11:41 AM - Re: SWR meter(s) NAV/COM/DME/TPD (D L Josephson) 2. 04:10 PM - Re: Making a LED landing light flash (Eric M. Jones) ________________________________ Message 1 _____________________________________ Time: 11:41:13 AM PST US From: D L Josephson Subject: AeroElectric-List: Re: SWR meter(s) NAV/COM/DME/TPD On 10/17/12 11:57 PM, AeroElectric-List Digest Server wrote: Conventional SWR meters require an external generator and power amp, as Bob mentions. The MFJ meters he suggests work fine for nav/com, but for L band (DME, transponder, UAT) you need something else. There is a good analysis of the various approaches at http://www.rigexpert.com/index?s=articles&fs ... they also make handheld devices that go to 1000 MHz but not far enough for transponder and DME (1215 MHz to get all of it.) The preferred approach is an antenna analyzer like the Anritsu Site Master series, which was developed for people installing cell phone base stations. The earlier versions go to 1200-1300 MHz and are being phased out because many cell phone networks now use frequencies at 1700 MHz and above. They sell for a little over $1,000 on ebay (or much more for the latest ones that go to 6 GHz or more.) In my toolbox now instead of an MFJ is a "Times Technology" T100+ network analyzer, which you can buy from the Hong Kong manufacturer for $250 on ebay, or see his website at http://timestechnology.com.hk. It is fiddly to use and seems rather fragile but works well, runs on two AA cells and fits in a shirt pocket. It will even draw a low resolution Smith chart to give you some idea of what your antenna is actually doing. It has a USB port and the fellow keeps promising to release a full PC control program but hasn't, although the demo example gives full details on what would be required if someone were to write one themselves. It only goes to 500 MHz though. -- David Josephson ________________________________ Message 2 _____________________________________ Time: 04:10:34 PM PST US Subject: AeroElectric-List: Re: Making a LED landing light flash From: "Eric M. Jones" Some notes on wig wags and flashers: This field has been studied since the 1800's since people were quite interested in making lighthouses visible to ships. Studies on what is most visible and how it is measured is an extremely difficult subject: Viz, a light visible at a flash pulse-width of 40 mS can appear to be LESS BRIGHT at 50 mS. WTF? (I hear you ask), well, the visual system is working as hard as it can to detect a shorter flash and sends a signal to the brain. Nothing happens beyond that while the visual neurons need time to recover. OR SOMETHING...Weird. (Broca & Sulzer 1902). I'm not sure anyone really knows, but it is an easy experiment to reproduce. Blondel-Rey equations are used to determine Effective Intensity Ie. In the last few years the methodology has been called into question because the Blondel-Rey equations don't work well except with purely square-wave pulses over a limited range. The B-R equations don't do so well with strange wave shapes, multiple flashes, complex flash chains, and many other complications. Nevertheless the FAA still uses B-R. The Cessna beacon was approved years ago and still complies with the old standard. The new FAA standard (which YOU must use) is much brighter. The best reason to use LEDs for brake lights is that the distance you need to stop when the guy in front of you stops is markedly increased due to not having the delay needed to heat up a tungsten lamp. This is much safer but probably has nothing to do with the wave shape and wouldn't help much in aviation. An LED engineer suggested to me that I use the newest board-mounted red LEDs because they can produce much higher-energy flashes (or even Ie) than white (or anything else). I intend to do so. Attached is my paper on LED beacons. The last couple paragraphs show their age. These beacons are easier and cheaper than they were 8 years ago. Comments appreciated. -------- Eric M. Jones www.PerihelionDesign.com 113 Brentwood Drive Southbridge, MA 01550 (508) 764-2072 emjones(at)charter.net Read this topic online here: http://forums.matronics.com/viewtopic.php?p=385645#385645 Attachments: http://forums.matronics.com//files/aircraft_beacons_using_leds_551.pdf ------------------------------------------------------------------------------------- Other Matronics Email List Services ------------------------------------------------------------------------------------- Post A New Message aeroelectric-list@matronics.com UN/SUBSCRIBE http://www.matronics.com/subscription List FAQ http://www.matronics.com/FAQ/AeroElectric-List.htm Web Forum Interface To Lists http://forums.matronics.com Matronics List Wiki http://wiki.matronics.com Full Archive Search Engine http://www.matronics.com/search 7-Day List Browse http://www.matronics.com/browse/aeroelectric-list Browse Digests http://www.matronics.com/digest/aeroelectric-list Browse Other Lists http://www.matronics.com/browse Live Online Chat! http://www.matronics.com/chat Archive Downloading http://www.matronics.com/archives Photo Share http://www.matronics.com/photoshare Other Email Lists http://www.matronics.com/emaillists Contributions http://www.matronics.com/contribution ------------------------------------------------------------------------------------- These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.