Because the 70cm elements are 1/2" too short. Kent Brittain analyzed the antenna and found that while the element lengths were correct for an antenna using elements insulated from the boom, they were too short for elements directly mounted to the boom. I add some 1/4" threaded aluminum spacers on each half of the element before I assemble the antenna, as to me, it was easier than modifying it so the elements were insulated from the boom. Does it make a difference? I'm sure it does on an antenna range, but having only one Arrow, I can't do an "A-B" comparison during a pass. I suppose I could hook it to my spectrum analyzer and point it at a 70cm repeater or weak signal source, but that's a bit difficult for me to do in my apartment! Maybe after I get all moved in with my girlfriend, and have a real backyard to play in! 73, Jim KQ6EA
--- On Sun, 8/16/09, Clint Bradford <[email protected]> wrote: From: Clint Bradford <[email protected]> Subject: [amsat-bb] Re: Modifying the Arrow Ant? To: [email protected] Date: Sunday, August 16, 2009, 11:36 AM .. I opted to try to insulate the elements from the boom ... Please remind me why you think any such modification to the Arrow is necessary. If we are discussing the Arrow dual-band unit for satellites with the duplexer built into the mast, I personally wouldn't dream of modifying it as you decribe. It works the FM birds phenomenonally as designed. The only 'mod' I consider is the addition of a handle for portable ops, a pictured at ... http://www.k6lcs.com Clint Bradford, K6LCS _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb _______________________________________________ Sent via [email protected]. Opinions expressed are those of the author. Not an AMSAT-NA member? Join now to support the amateur satellite program! Subscription settings: http://amsat.org/mailman/listinfo/amsat-bb
