Don't know if they make an Invar flame suit, but I may need one :) What I have done in the past is obtained a piece of stainless "redi-rod" and short coupling nuts (female on both ends) with the same threading as the Sinclair.
I then lengthen the rod by only the amount required by cutting the coupling nut and redi-rod "studs" to only lengthen the entire rod by 3/4" or so. This small amount when heated will only expand a fraction. It may be just what you need to counteract the contraction of Invar as it is heated. I have three duplexers in service (Q202 style) that have never had an issue. Although the temperature is pretty steady at my site. I even put them in a freezer and left them out in the sun, and there was no change in the notches or pass loss over about 50 degrees temperature difference... And yes I had a large deep freezer :) Dave Cameron VE7LTD --- In [email protected], "Chuck Kelsey" <wb2...@...> wrote: > > 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" <wb2...@...> > 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" <imashf...@...> > > 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" <b...@...> > >> 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 >
