To expand on my comment, the invar rod is there to minimize the temperature lengthening and shortening the center "probe." The original design with the invar to the bottom of the piston, keeps the overall length the same and allows temperature expansion to occur at the finger stock - thus not changing the overall length.
If you rotate the piston, then the piston itself can expand and contract, and change the overall length. Not as much as if no invar was used, but it will be worse than if it were kept attached were it was designed. Chuck WB2EDV ----- Original Message ----- From: "Chuck Kelsey" <[email protected]> To: <[email protected]> Sent: Sunday, July 18, 2010 8:55 AM Subject: Re: [Repeater-Builder] Re: Invar Rods > Not a good idea. They are attached to the "bottom" to keep the expansion > minimized. Turning them around will defeat the purpose of having the invar > in the first place. > > Chuck > WB2EDV > > > > ----- Original Message ----- > From: "IM Ashford" <[email protected]> > To: <[email protected]> > Sent: Sunday, July 18, 2010 8:54 AM > Subject: Re: [Repeater-Builder] Re: Invar Rods > > >> Just a thought, >> >> Why dont you turn the pistons around to give you a longer reach? >> >> Ian >> G8PWE >> ----- Original Message ----- >> From: "Burt Lang" <[email protected]> >> To: <[email protected]> >> Sent: Saturday, July 17, 2010 4:08 PM >> Subject: Re: [Repeater-Builder] Re: Invar Rods >> >> >>> What diameter are the rods? The older Sinclair VHF Hi cans used 5/16in >>> diameter whereas the newer cans used 1/4 in daiameter. >>> >>> burkleoj wrote: >>> > Glenn, I need 6 of them for a Sinclair duplexer that I have. >>> > >>> > Someone cut the rods off when it was originally on a commercial >>> > frequency. The rods in my duplexer are so short that it will not tune >>> > below 147 MHz before they disappear inside the top of the cavity. >>> >>> Very common when the frequencies are in the high 160s >>> >>> > >>> > I can get some dimensions for you to see if the ones you have may >>> > work. >>> > >>> > Thanks, Joe - WA7JAW >>> >>> You can buy invar rod material from some metal suppliers but you won't >>> like the price. It normally comes in 12ft lengths but the dealers will >>> cut it in half in order to ship UPS. The last time I bought some (around >>> 1990) the price was $30/lb. The dealer was Diezel (or Diesel) Metals on >>> Long Island somewhere. I still have some left from that order. >>> >>> FYI Invar is an allow consisting of exactly 35.16% nickel with the >>> remainder iron. It is magnetic and will corrode in a damp environment >>> leaving a green "rust" on the surface. >>> >>> Burt VE2BMQ >>> >>> >>> ------------------------------------ >>> >>> >>> >>> Yahoo! Groups Links >>> >>> >>> >> >> >> ------------------------------------ >> >> >> >> Yahoo! Groups Links >> >> >> > > > -------------------------------------------------------------------------------- > > > > No virus found in this incoming message. > Checked by AVG - www.avg.com > Version: 9.0.839 / Virus Database: 271.1.1/3013 - Release Date: 07/18/10 > 02:35:00 > > > > ------------------------------------ > > > > Yahoo! Groups Links > > > -------------------------------------------------------------------------------- No virus found in this incoming message. Checked by AVG - www.avg.com Version: 9.0.839 / Virus Database: 271.1.1/3013 - Release Date: 07/18/10 02:35:00
