Yep... I haven't had my coffe yet, and wife distracted me several times. Thanks for the catch... I stand corrected. nothing worse than bad info.. ;-) The CB'ers only move around a couple of kHz.. this guy has the potential to move a couple of mHz.. that could make it ugly considering the normal bandwidth of a vertical... folded dipoles are generally broadband by nature, and very forgiving. I was assuming the "twin-trucker" vertical arrangement.
Thanks again for catching my error.... all the more reason for peer review! mike -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of Paul Kelley Sent: Saturday, April 30, 2005 10:32 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] antenna's Good answer Mike, but I think you made a typo below... If the antennas are 50 ohms and you feed them with odd quarter waves of 75 ohm coax, the impedance is transformed to 100 ohms... divided by 2 at the T connector is 50 ohms, not 37.5. In theory I agree with the comment about not moving too far from the design frequency, but in practice I suspect it will be a little more forgiving. I have built phasing harnesses this way for 2 and 4 dipole arrays (base / repeater antenna) and they cover a fairly wide range before the impedance gets out of hand. BUT, the bandwidth of the antennas themselves will be a BIG factor here... Paul N1BUG Mike Perryman K5JMP wrote: > You can create a 50ohm "match to split" by using RG-59 is > 75ohm (and is lossy as hell at 2m, but for the sake of > argument please bear with me.) cable cut to an odd > multiple of a 1/4 wave length combined with a > T-connector. > > Feed the T with standard 50ohm line. Assuming a purely > resistive load, the two lines in paralell will present a > resistance of approx 37.5 ohms. This is close enough. > And I am NOT going to get into complex impedances here. Yahoo! Groups Links Yahoo! Groups Links <*> To visit your group on the web, go to: http://groups.yahoo.com/group/Repeater-Builder/ <*> To unsubscribe from this group, send an email to: [EMAIL PROTECTED] <*> Your use of Yahoo! Groups is subject to: http://docs.yahoo.com/info/terms/
