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
| INDEX | Back to Main INDEX |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | 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
| INDEX | Back to Main INDEX |
| PREVIOUS | Skip to PREVIOUS Message |
| NEXT | Skip to NEXT Message |
| LIST | Reply to LIST Regarding this Message |
| SENDER | Reply to SENDER Regarding this Message |
|
| Subject: | Re: Making a LED landing light flash |
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
These Email List Services are sponsored solely by Matronics and through the generous Contributions of its members.
-- Please support this service by making your Contribution today! --
|