On Aug 14, 2010, at 9:45 PM, Jeff DePolo wrote: > Well, kinda. Many duplexers are spec'ed for 1.5:1 (14 dB RL) input VSWR > max. Fortunately, I rarely see any that are that bad. I'll gladly trade > off a tenth of a dB of insertion loss for several (if not 10 or more) dB of > return loss improvement when I'm tuning on the VNA, but some hams are greedy > and don't think along those lines when they're tuning...
Actually I think that even though Service Monitors have finally become *relatively* commonplace in the Ham Shack, the VNA is not something "most" hams have seen or know how to use. (I would count myself in that group.) Like Service Monitors used to be before the flood of HPs on eBay in the last few years, I hear rumors of "great deals" on VNAs, and yet never see them in any way "plentiful", "easy to acquire", or "affordable", but then again I'm also not exactly looking that hard, and perhaps I'm missing one of those "everyone knows about Bob's VNA Warehouse!" kinds of sources for such things. I do find it interesting (sorry another side-thought) that a great many *professionals* don't seem to have access to them, nor can convince their employers to purchase them. I have heard the excitement in professional RF Engineer's voices when their company finally acquires one... and seen 'em load up the car with stuff they've "always wanted to put on the VNA". A few years ago, anyway. Are they more common than I think? >From Jeff's comments and other's off-list, they're obviously the "right tool >for the job", and tuning duplexers without them seems similar to messing >around with taking the engine out of a car without an engine hoist, but unlike >engine hoists -- professional RF shops don't even seem to regularly own a VNA >or have anyone on staff qualified/trained on how to use one. Can't count the number of cell site and other RF techs I've talked to over the years who were just happy as clams when they finally got TDR equipment to check cables too. What's up with the RF industry not buying these things by the truckload? Too spendy? -- Nate Duehr, WY0X [email protected]
