There can be no one size fits all ladder line length for a multiband antenna. Allot of variables come in to play such as other nearby antenna's, trees, power lines, etc that interact with a multi band antenna in an unpredictable manner.
I use a fan doublet with individual elements for 80, 40, 20 and 10 meters and it is fed with 122 feet of 300 ohm window line to a balanced Johnson Viking Matchbox http://www.kn4lf.com/kn4lf36.htm . It works very well on 80-10 meters including the WARC bands. I do have a bit of RFI on 40 meters if I run PSK31 at an output power above 50 watts. I have varied the length of the window line between 100 and 130 feet with no change on the RFI situation on 40 meters. Using the same antenna with an old MFJ-989B tee network antenna tuner I had RFI on almost all bands. 73 & God Bless, Thomas F. Giella, KN4LF Lakeland, FL, USA [EMAIL PROTECTED] PODXS 070 Club #349 Feld Hell Club #141 30 Meter Digital Group #691 NA QRP CW Club #1723 Straight Key Century Club #3097 KN4LF Amateur & SWL Autobiography: http://www.kn4lf.com
