At 7/31/2010 07:04, you wrote:
>Bob, > >Some of us are geographically disadvantaged when it comes to availability >of equipment. Here in rural Australia, anything secondhand for Amateur >Repeater construction is rare, shipping of anything is expensive. From >what I read on the group, the U.S. Is overloaded with surplus equipment, >sometimes at bargain prices. For me to buy and ship that "cheap" 1/4 wave >can and pre-amp would be more expensive than buying a new Simrex >Pre-Selector :-) I don't believe that. But if you want NEW coaxial resonator filters: http://anglelinear.com/filters/coax_filters.html' These are actually a bit smaller than your typical cavity resonator, & they're very low loss. Apparently Chip decided to tradeoff a bit of Q to keep the loss low. But with 2 resonators you end up with a very low system NF & selectivity only a bit less than the GLB (which is misleading, as I explained in my previous post because some of that selectivity is after the preamp, so it's still partially susceptible to OOB overload). If you factor in the ham discounts, the total for the dual coaxial resonator/preamp combo is a bit more than the Simrex preselector. But we KNOW the NF will be ~1.1 dB, we KNOW that ALL of the preselection will be ahead of the preamp, so with that info we can properly design a RX system. The Simrex units are made in the US, so you still have to pay to have it shipped down unduh. >IF the Simrex-GLB product did not perform..........the word would spread >faster than the Black Plague and no one would buy them........ Not saying it doesn't work, but I am saying as an RF engineer that it's impossible with the data in hand to properly apply it's use in a repeater system. Bob NO6B
