The best PL filter I ever saw was one I built out of a digital SCF design a couple of years ago. I realize that the paper is referencing commonly available products, but I wish someone would make this thing up for sale.
Here is a link to the data sheet: http://www.mix-sig.com/Msi5data12.pdf This thing had essentially flat response from 110% of Fc to the top of the voice band. The cutoff below was superb in the elliptic mode. If Fc was set to 300Hz, tones at 255Hz were 30 dB down. It got better with lower frequencies, and everything below 200Hz was 70+ dB down. If set to Fc of 275Hz, everything was flat above 300, and 234Hz was 30dB down, and everything below 180 Hz was better than 70 dB down. The neat thing is it is totally adjustable and can be built with only two 8 pin ICs and a few cheap parts (caps and resistors). If all of your PL tones are in the lower ranges, Fc can be set to 200Hz (or lower), giving fuller sounding voice audio while still rejecting tones below 170Hz by 30dB or more, a lot more as you go lower. Joe --- On Sat, 9/13/08, [EMAIL PROTECTED] <[EMAIL PROTECTED]> wrote: From: [EMAIL PROTECTED] <[EMAIL PROTECTED]> Subject: [Repeater-Builder] CTCSS highpass filter paper To: [EMAIL PROTECTED], [email protected] Date: Saturday, September 13, 2008, 9:32 PM Hi All, There was a discussion on Repeater-Builder a while ago about the advantages and disadvantages of various commercial CTCSS highpass filters. S-COM's analog guru, Virgil, W0INK, did a careful analysis of five common highpass filter designs: Comm Spec TS-32, Comm Spec TS-64, Micor PL, MSR2000 PL, and GE CG. The results are certainly interesting. His paper can be found at http://www.scomcont rollers.com/ downloads/ ctcsssreject&hpfilters.pdf Enjoy! 73, Bob Bob Schmid, WA9FBO, Member S-COM, LLC PO Box 1546 LaPorte CO 80535-1546 970-416-6505 voice 970-419-3222 fax www.scomcontrollers .com
