Dave, Having looked at the GB3FH website,this duplexer looks to be self compensating.
Any expansion due to heating of the heliax inner should be compensated by expansion of the linking feeder inner,pushing the tuning bar upwards. I have doubts as to the small effect on tuning that 0.2mm expansion on a 1.3m stub would have (0-40 degC) I also have doubts that an inner constrained and corrugated in foam would self expand in the first place. I think this design could be ideal given some R&D time and a little patience..I have my eyes on a 25m piece of 1 5/8" at the moment in the Oxford area.. I just need to persuade the owners that I am not a scrap metal capitalist and need the stuff for a genuine non-profit purpose.. will keep you posted Ian G8PWE Walsall UK ----- Original Message ----- From: dave_g7uzn To: [email protected] Sent: Thursday, December 14, 2006 3:37 PM Subject: [Repeater-Builder] Re: 6M duplexer wanted in UK Are you saying that a duplexer built from heliax can cope with a 0.5MHz plit at any temperature?....I somehow doubt it (no invar!) Cheers Dave UZN --- In [email protected], "Matt Beasant" <[EMAIL PROTECTED]> wrote: > > Hi Steve, > > The 'FH duplexer was built by a very good friend, who doesn't want to build another one!!! > > But yes, it was built from LDF7-50 1 -5/8" Heliax. > > Matt > ----- Original Message ----- > From: Steve > To: [email protected] > Sent: Wednesday, December 06, 2006 5:14 PM > Subject: Re: [Repeater-Builder] 6M duplexer wanted in UK > > > Hi Matt > > What size heliax did you use, I seem to remember that it was built for you, wasn't it. I tried myself with small dia stuff > and it was not very good, went slightly off tune and of course > rx desense. As I have said, itmay just have been the cable I used. > > 73 > > Steve > ----- Original Message ----- > From: Matt Beasant > To: [email protected] > Sent: Wednesday, December 06, 2006 4:06 PM > Subject: Re: [Repeater-Builder] 6M duplexer wanted in UK > > > My heliax duplexer has been in service now for over 2 > years at GB3FH without fault or need to re-adjust. > > I check it every time I visit site and it never moves! > > Over 85dB rejection on one side and 90 odd dB on the > other, works fine for me. > > You can see pictures of it at www.gb3fh.org.uk > > Regards, > > Matt, G4RKY > --- Steve <[EMAIL PROTECTED]> wrote: > > > Hi > > > > don't get me wrong, Iam not condeming heliax > > duplexers > > totaly, but you have to take into account > > reliability once on site. I did make one but had to > > scrap it as it was so unreliable causing de sense > > etc, and every time I had to look at it I had to > > make arragements to access the site, which could > > take upto 2 weeks, must point out the one I > > made used small dia heliax, maybe larger dia would > > be OK > > but as I can't get any, I don't know > > Anyway had my say so end of thread from me > > > > Steve > > ----- Original Message ----- > > From: Barry C' > > To: [email protected] > > Sent: Wednesday, December 06, 2006 11:25 AM > > Subject: Re: [Repeater-Builder] 6M duplexer wanted > > in UK > > > > > > > > Being a fan to the exclusion of saving several > > hundred quid is rather silly > > when the duplexers work well and are generally > > quite efficient . > > > > >From: "Steve" <[EMAIL PROTECTED]> > > >Reply-To: [email protected] > > >To: <[email protected]> > > >Subject: Re: [Repeater-Builder] 6M duplexer > > wanted in UK > > >Date: Wed, 6 Dec 2006 11:07:54 -0000 > > > > > >Hi > > > > > > think you will find that Dave, like me, isn't a > > huge fan > > >of Heliax duplexers, see my posts about actualy > > getting > > >hold of ldf 750 > > > > > >73 > > > > > >Steve > > > ----- Original Message ----- > > > From: Mr John Lloyd > > > To: [EMAIL PROTECTED] ; > > [email protected] ; John > > >Lloyd > > > Sent: Wednesday, December 06, 2006 6:56 AM > > > Subject: [Repeater-Builder] 6M duplexer wanted > > in UK > > > > > > > > > Dave, > > > > > > You can build your own 6 Mtr duplexer. Find some > > 1-5/8 > > > heliax and put one together. > > > > > > Look at http://www.wa7x.com/ki7dx_rpt.html > > > > > > Thanks, > > > > > > John, K7JL > > > > > > Utah VHF Society > > > > > > http://utahvhfs.org/snowlink.html > > > > > > 1a. 6M duplexer wanted in UK > > > Posted by: "dave_g7uzn" [EMAIL PROTECTED] > > > dave_g7uzn > > > Date: Tue Dec 5, 2006 3:20 am ((PST)) > > > > > > Hi All, Is anyone with a set of cavity filters > > > suitable for 50/51MHz > > > brave enough to sell them to me and get them > > shipped > > > to the UK for a > > > 6M repeater project? ALL expences will of course > > be > > > covered. If you > > > can help please email me direct at > > > > > > [EMAIL PROTECTED] > > > > > > > > > __________________________________________________________ > > > Need a quick answer? Get one in minutes from > > people who know. > > > Ask your question on www.Answers.yahoo.com > > > > > > > > > > > > > > > > > > > > >---------------------------------------------------------- > > > > > > > > > No virus found in this incoming message. > > > Checked by AVG Free Edition. > > > Version: 7.5.432 / Virus Database: 268.15.9/573 > > - Release Date: > > >12/5/2006 4:07 PM > > > > > > > __________________________________________________________ > > Advertisement: It's simple! Sell your car for just > > $20 at carsales.com.au > > > > > http://a.ninemsn.com.au/b.aspx?URL=http%3A%2F%2Fsecure%2Dau% 2Eimrworldwide%2Ecom%2Fcgi%2Dbin%2Fa%2Fci%5F450304%2Fet%5F2%2Fcg% 5F801577%2Fpi%5F1005244%2Fai% 5F838588&_t=757768878&_r=endtext_simple&_m=EXT > > > > > > > > > > > > > > > ---------------------------------------------------------- > > > > > > No virus found in this incoming message. > > Checked by AVG Free Edition. > > Version: 7.5.432 / Virus Database: 268.15.9/573 - > > Release Date: 12/5/2006 4:07 PM > > > > __________________________________________________________ > Do you Yahoo!? > Everyone is raving about the all-new Yahoo! Mail beta. > http://new.mail.yahoo.com > > > > > ---------------------------------------------------------- --------- > > > No virus found in this incoming message. > Checked by AVG Free Edition. > Version: 7.5.432 / Virus Database: 268.15.11/575 - Release Date: 12/6/2006 12:22 PM >
