On Sat, 15 May 2010, spradio2000 wrote: > Hello, I've been designing and building my own cavities, and > experimenting to find out what works best. The current project is a > 70cm repeater, but we are planning on a 2m repeater.
> My own design uses a length between 1/4 and 1/2 wave between the > cavities, this looks better after tuning with the coupling loops. > > Before I continue with 2m cavities I'd like to know more about > coupling cavities and cable lengths. What is wise, and is the setup > with 2x twoo notches and one bandpass the best solution. I tried 2x > tree notches. works nice but requires major retuning when connected to > the repeater. > > I hope one has some good info, or knows where to find some. > > Oh, all interconnecting cables are RG400 double shielded, silver and > PTFE cable. Did you calculate the distance to include connectors and velocity factor of the coax? 1/4-wave between points is normal; it also tends to have a transforming effect as well that helps with matching. Another thought might be to aperture couple the cavities. Then you won't have any cable or connector issues to deal with. The paging cans use this to reduce losses and increase power handling capability. -- Kris Kirby, KE4AHR Disinformation Analyst
