Hi All Are the loop antenna's no longer a good idea. And also it seems to state that bigger is better in some of the text's relating to the flarm antenna. Any comments ? Cheers Mark
From: [email protected] Date: Sun, 17 Apr 2011 21:03:27 +1000 To: [email protected] Subject: Re: [Aus-soaring] Antena length for Oz Flarm Hi Jeff Thank you and belatedly to Ian. That confirms exactly what I was thinking regarding the length. I just was not sure that my conclusions were correct. Cheers Paul On 17 April 2011 20:47, Jeff Farrow <[email protected]> wrote: Paul I attach an email that Ian McPhee sent to this list last year. An explanaation for the discrepancy. Jeff Farrow From: [email protected] [mailto:[email protected]] On Behalf Of Ian Mc Phee Sent: Thursday, 10 December 2009 8:24 AM To: Discussion of issues relating to Soaring in Australia. Subject: [Aus-soaring] many OZFLARM comm (stick) aerials in use may well be the wrong aerial (far too short) Been troubled by some lack of performance in OZFLARMS for some time now and only yesterday after talking to Mark Fisher realised many of the stick communication aerials on OZFLARMS may well be wrong frequency. I do know 4 in our club are wrong length and the fifth glider has one of those Mobile one long range aerial which gives you green LEDs well beyong what the eye can see even 4 to 5 km!!! My calculation for 900mhz is the 1/4 wave aerial 75 to 80mm long. At our club 4 the little white aerial say 40 mm long - far too short. It would seem the little person in China threw all the say 900MHz and either 1800 or 2400MHz aerials in the one box as they looks the same on the outside. I urge as many people as possible this weekend pop the rubber cover off the aerial and inspect the inside aerial length I am predicting 50% of the aerials will be the wrong length - far too short. Job will take less than 1 minute. It would be easy to add a little copper wire of the right length While on Flarms etc I can say GPS (flat aerial) are best placed 25cm apart as the GPSs can interfer with each other. Also in motorglider if you are using the engine battery I would suggest fitting a 22000uF capicator in the power lead near flarm I will be very interested to hear the results of the aerial wore length Ian McPhee No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.717 / Virus Database: 270.14.116/2580 - Release Date: 12/22/09 06:13:00 ----- Original Message ----- From: Paul Bart To: Discussion of issues relating to Soaring in Australia. ; Chat DDSC Sent: Sunday, April 17, 2011 12:31 PM Subject: [Aus-soaring] Antena length for Oz Flarm Hi I have become concerned that the range at which my Flarm detects gliders is not anywhere near specification. It often bypasses the green warning, going straight to red. I understand that there are many factors in play, such as shielding from the instrument panel, carbon etc., but I do not think that this is the explanation in my case. So I thought I would invest in a better antenna, but before I did that I had a look at the standard antenna provided. When I removed the plastic covering I was surprised that the actual antenna was only 48 mm long. Yet the manual states, that the antenna at 1/4 wavelength should be 86 mm long. I also have the original Swiss Flarm (inherited from a glider purchase from Europe) so I compared and its antenna is approximately 80 mm, but as the cover is not removable, I cannot confirm the length of the actual conductor. Anyway I had a look at a few wavelength calculators on the web and given the average frequency the Oz Flarm operates on is about 921MHz, the 1/4 wavelength should be approximately 77mm and not the 86 indicated in the manual. I haste to add here that I know next to nothing about antenna design, so a simple application of the formula might not be correct. In any case though, the length of the antenna on my Flarm is 48 mm, well short of the manual stated 86 mm. So I would like to ask those that know more then I on this topic 1) Is 48 mm the correct length (too long for 1/8 and too short for 1/4 wavelength) 2) If not, should it be 86mm as per manual, or 77mm as per calculated length 3) If mine is NOT an isolated case and the 45 mm length is not correct, are we having a fleet of Flarms out there with much poorer range and hence effectiveness that we should have. Any help on the topic greatly appreciated Cheers Paul _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring _______________________________________________ Aus-soaring mailing list [email protected] To check or change subscription details, visit: http://lists.internode.on.net/mailman/listinfo/aus-soaring
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