Mark, I think 3M 1170 tape is the best choice. It is 2 mils thick, with a 1.2 mil layer of conductive acrylic adhesive. I prefer a smooth aluminum tape to an embossed tape, simply because I think distributed contact with conductive adhesive is better for RF than point-contact tape with non-conductive adhesive. The stuff isn't cheap, of course, but it is a product that you don't use a lot of, but you need it when you need it. Kinda like Stabilant 22A. Here's the product sheet: http://tinyurl.com/62q8bp Notice that 3M also offers copper shielding tape, which is nice if you need to solder to it. And, for the really wealthy folks, there's also gold tape! I think I'll just stick (pun intended) with the blue-collar aluminum stuff...
73, Eric Lemmon WB6FLY -----Original Message----- From: [email protected] [mailto:[EMAIL PROTECTED] On Behalf Of n9wys Sent: Tuesday, August 26, 2008 9:38 AM To: [email protected] Subject: RE: [Repeater-Builder] De-Sense and Circulator Question OK, I found the message. now the question: what aluminum tape is best for this? Or is there a "best" tape? I just got a Motorola duplexer for a 462 repeater I'm building, and it has the holes/slots in it. (And yes, it *IS* a MICOR.) Of the various types of tape available, does the adhesive need to be conductive? Or is it "good enough" for the foil to merely cover the openings? For example, I was browsing Mouser's choices of tape HERE <http://www.mouser.com/catalog/635/2090.pdf> ... http://www.mouser.com/catalog/635/2090.pdf <http://www.mouser.com/catalog/635/2090.pdf> I am interested in these tapes: 3M 425 or 427 (adhesive conductivity not listed) 3M 1170 (listed: "conductive adhesive") Although I'm thinking at these costs, they must ALL have conductive adhesives... 425 (1" wide) costs $20.93/roll; 427 is $61.95/roll; and 1170 is $46.07. If anybody has insights, I'd be interested to hear! Thanks, Mark - N9WYS -----Original Message----- From: [email protected] On Behalf Of Eric Lemmon As I and several others have noted earlier, the Motorola T-1500-series duplexers are barely adequate even with a 5 MHz split. Nevertheless, Motorola shipped thousands of Micor repeater stations with this duplexer, and they worked fine. But, keep in mind that a Micor 75-100 watt PA was a very good design and far more stable and noise-free than most aftermarket power amplifiers. The crystal-controlled Micor exciters are inherently less noisy than the synthesized exciters used in newer and less-expensive repeaters. The extremely sharp, crystal-controlled Micor receivers were better able to shrug off nearby carriers or noise than many- if not most- modern synthesized receivers. Even if your T-1500-series duplexer is optimally tuned, you can possibly improve its performance a bit by using adhesive-backed aluminum tape to cover the slots where the loop and probe adjustments penetrate the side walls of the cavities. The metal tape will eliminate a possible leakage path through the slots. Your jumper cables should be made of RG-400/U or RG-214/U cable with the proper connectors on each end- no adapters. Crimped-on, silver-plated connectors are more reliable than those that are soldered or clamped.
