I built a set of 6 meter notch filters using this web site: http://www.dallas.net/%7Ejvpoll/dup6m/dup6m.html (I found this site by doing a search on repeater-builder.com) I had great results with them. They have shorted ends.
Here is a site talking about 2 meter with OPEN ends.. http://www.xs4all.nl/~pa0nhc/Projects/IMDfilter/CableNotchFilter145MHz/KabelNotchFilterV10EN.htm Check out both of these websites. They will definitely help with understanding notch filters. An open cable 1/4 wavelength will appear "shorted" to the signal input at its frequency. A shorted cable 1/4 wavelength will appear "open" to the signal input at its frequency. (a combination can be used to make a BP-BR (band pass, band reject) duplexer.) If someone would confirm this, I would appreciate it. That is what I remember. Check me out. Coax size matters, but I don't have a reference. Also, remember that the VELOCITY FACTOR must be considered when calculating bandwidth. This is something that is known on certain types of cable. (example: RG-58 is 66%) John Clark, KI4AWK WCTV 6 Television Engineering (850) 893-6666 EXT 205 [EMAIL PROTECTED] ----- Original Message ----- From: <[EMAIL PROTECTED]> To: <[email protected]> Sent: Thursday, October 14, 2004 2:26 PM Subject: [Repeater-Builder] Coaxial Stub Theory > > Ok, So you can make some kind of filters by placing a "T" in line with a piece of equipment and cut the Coax for 1/4 wavelength at the desired frequency. > > But What is the difference between a shorted stub and an open stub? > > Also does coaxial size determine bandwidth, and if so does anyone have a chart of what cable does what? > > I am intrested in making a coaxial stub duplexer for 2 meters and 6. My original concept is for 1 1/4" copper tubing for the outter conductor and 1/2" copper rod for the center. > 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/
