Certainly not what I was expecting... Yeah, I bought one from 'that guy'. It's more than an untrained eye - he straight lied to me... said 'under these caps are where you'll tune the capacitors' - I should have popped one off and looked down the hole. Maybe he was clued in, maybe he wasnt - either way, that's what I bought. Dangit :P
So if all I have are pass cavities.... what 'are' they good for ? Guess I've got to find another dupelxer. j --- In [email protected], "Jeff DePolo" <j...@...> wrote: > > > Ok so here's what I've got (I think) > > > > http://www.n2ckh.com/FORSALE/REPEATERS/DUPLEXERS/DB4076/DSC02678.JPG > > > > Hamvention special, 4 cavities, appears to be a DB Products > > 4076 family unit. My bench tools: HP 8924c w/ Spec Analyzer > > and Tracking Generator. > > There was a guy at the Hamvention that had several sets of Decibel > four-cavity window filters, selling for $50 each, which, to the untrained > eye, would look like an older DB4076. As you said, there would be nothing > in the hole where the capacitor would be in a regular DB4076. In essecence, > what you have are just plain-jane pass cavities. > > As a second means of confirming that you do, in fact, have a window filter, > is there an antenna "tee", or are the four cavities cabled together in > cascade? If the latter, then you probably have a window filter. > > And as a third means of confirming, is there is a label on the front? If > not, was there any signs of a label having once been there? If not, then > that's yet one more indication that it isn't a DB4076. > > Decibel made two varieties of pass cavities used in window filters in that > era. One had adjustable loops (less common), the other had fixed loops. If > your loop connectors have a rectangular chrome plate around them with > insertion loss calibration marks, you have the less-common adjustable ones. > If you just see four philips-head screws and no chromed plate around the > connectors, then yours is not adjustable. > > If you have the adjustable type, you could probably use them as a pass-only > duplexer, but with mediocre isolation, even with the insertion loss cranked > up higher than you'd like. If you have the non-adjustable ones, they have > very tight coupling, so you're not going to get the isolation you'd need for > a repeater. > > > Did I buy a piece of junkola? Teach me obie-wan. > > Not junk, but maybe not what you were expecting... > > --- Jeff WN3A >
