Neal, I do not have any Pic's that I can locate. This was built before digital cameras were affordable to the common man. We did take Polaroid's, but whoever has them by now are well faded. There is one fellow ( forget his name) on this list that took my description and made a very nice set of cavities. He really went all out, he had machining skills and equipment. He almost duplicated a DB products can when he was complete. He used fancy finger stock and piston caps. Very nice job. Maybe we will get him to chime in.
The example I followed to make the loop was the write up on converting the db products pass cavity to a pass/notch. I have seen many articles on the web on making the loops for the cans. A very good write up on this by Jeff DePolo can be found at this link. http://www.repeater-builder.com/loband/ I did not use his method of using coax stubs to make the notches. But this is a good source of information and constructions techniques. The project was done by myself and a hand full of other hams. We took a look at a wacom duplexer and did the best we could with common parts to make something like it. Each person in the group had certain skills or equipment for making the parts. The first one we completed checked out on an IFR 800A with 22db of notch with .6 or so db of insertion loss. (not bad, could be better. Maybe using Jeff's notch setup would be better?) We compared this to others that had made these duplexers. What we found was the construction of the top plate was the most critical part of how well the cavity would work. It was common to make the top with a paint can lid or sheet metal. Theses all has poor notches and high insertion loss. The thick aluminum plate seems to work the best. Also the plexi-glass stabilizer in the can prevents the long tuning rod from moving around. Also we were the only folks to use the stove pipe crimp to fit the cans. This made the cavity very strong. all others just soldered the cans with a butt joint. We used no drawings just looked at the wacom and other coffee can cavities and went from there. I was not the first to make a set of coffee can duplexers but think we took them up a notch! (pun intended) I think I might be the only repeater still running a set. Currently the longest running set. The picture on the repeater site on my web page does not show the duplexers well as they are back in the corner behind the repeater racks and coupler array. I will see if I can get some better pictures. It is ruff as I am on the east coast now and repeater is on the west coast. I have not been to the site in 7 years. The next set was done with irrigation pipe, Yet to be finished. Still sitting here somewhere. I think I am using one tube to hold all my mobile antennas! If you have someone that is good with a tig you can weld them up. If not then just make the bottom just like the top. This is how crafty we got. to make the top plate we did not have a lath to make a clean round disk. We chucked up the square plate in a drill press at low speed and made a cutter that was held in place with the bench vice! Touched it up on the sander and bingo! It is not that critical when making LB cavities. You do not need invar or copper plating or anything like that. It is just not that much difference at these frequencies. Now vhf hi and up and you bet! It is very critical what you use and how you build it. Shoot look at the heliax cavities out there! You can not get much cruder than that in construction. Kevin King SCSA BSCIS ARS KC6OVD GMRS KAG0378 EIEIO 2722 Acworth Georgia -----Original Message----- From: Repeater-Builder@yahoogroups.com [mailto:[EMAIL PROTECTED] Behalf Of Neal Newman Sent: Sunday, July 24, 2005 2:55 AM To: Repeater-Builder@yahoogroups.com Subject: Re: [Repeater-Builder] Still after Hey Kevin You have any Picsof this Or Diagrams On making the loops and Pass Notch info Caps ect. Ive Been looking for a while for 6 meter cans.. I have 1 5/8 hardline was going to Build a Helix Duplexer. How long are the cavites? why not just Use Stovepipe and Cap both Ends? Neal 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/
