I have built cans in the past and would NEVER do it again. It is a waste of time. As the metals expand and contract, so does the tuning. The main tuning rod shafts are the biggest problem. The metal needs to have ZERO coefficient of expansion properties. Unless you have access to such material, DON'T GO THERE! I had to tune the cavities I made around 7 times a day in a relatively stable but not totally stable temperature atmosphere. Yes, it is a very good learning experience so you can appreciate how good a commercial set really are. The can changes can be minimized by making use of a VERY LARGE diameter can, such as a metal garbage can, so its change has little effect on the center section. (The closer the can is to the center 1/4 wave section, the more interaction will occur). But, you can't cheat with the center section. ZERO coefficient of expansion metal is vital. I can assure you, you will never be happy with a home made duplexer.
----- Original Message ----- From: Steven Samuel Bosshard \(NU5D\) To: [email protected] Sent: 12/25/2006 7:02:35 PM Subject: Re: [Repeater-Builder] Re: 6M cans made from other metals Jack, I believe the British Beer Kegs lack sufficient temperature stability and dynamic range because Budweiser is best at around 34 to 36 deg F, and I understand Guinness never gets much below room temperature, hence the lack of dynamic range may pose an impediment. Maybe an oxygen cylinder used in welding might have a better l/c (length / circumference) ratio? 73, Steve NU5D
