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Hi Malcolm
The 1/4 will easily cover the 500khz at that frequency. I'd also suspect that even if you went to (say) a colinear antenna to keep the radition lower to the ground, there would be more than enough signal going "upwards" to the aircraft.I guess you cant actually measure signal strength of received aircraft? You may even find that (say) the lower angle of a 5/8 whip actually helps when the aircraft are some distance away... I think the most important factor for comms with the winch site is to get both antennas as high as possible and if using a long coax run make it low loss. You have already indicated problems in this area. Possibly the winch install needs to be easy to knock down without damage? Apologies for not being specific.. Cheers Bob VK2YQA Malcolm Austin wrote: Hi, I have an interesting problem which I'd like to put to the newsgroup for idea's. Our club (gliding by the way) uses just a few frequencies to transmit (AM) and receive on. The main freq' is 129.975, but we go down to 129.900 and up to 130.400. We need some new antenna's but I'm wondering what would be the best. Currently we use a quarter wave set for 129.975, but this is I'm afraid just cut to a length (the lads are pilot's and not Ham's !!) The quarter wave of course is good in one respect that we are all hopefully up in the air so the high angle of radiation helps. It would be good though to improve the signal to our winch which is just 950 metres away (3100 feet for some!) but over the hill so to speak, so not line of sight. We struggle at times on our max 1 watt output to hear each other. I'm wondering what I can build that will help this low angle but leave the high angle still there. Also it would help, to have the VSWR band width with us and not against us on all the frequencies. For the winch we have limited height available on the top due to hangerage restrictions. If I build something big and solid, some one is sure to forget and rip it off going into the MT hanger. Our base end is a good old English double decker bus, so we have a good ali ground plane some 20 feet in the air. None directional capabilities are of course required as we fly 360 degrees around the club. Any thoughts out there? Many thanks, Malcolm - Radio Ham and Glider pilot. |