On Mon, 8 Sep 2008 11:59:09 -0500 "John" <[EMAIL PROTECTED]> writes: > Brian, > > It is true that the tuner isn't in line during receive. Schematics are > available with the service manual. If you have additional questions I > recommend you contact our senior design engineer [EMAIL PROTECTED] > off line or call 512 692-9044. > 73 > > For that matter, if it is true that the tuner cannot be placed in the > RX path, I am disappointed. On higher bands a good antenna match means > better system noise figure.
This brings up an interesting design issue (not specific to the F5K, but sort of generalized). On a radio with multiple receivers, and multiple antennas, the whole "how do you configure a matching network" becomes "interesting". I suspect that everyone tends to think in terms of the standard-for-40-years model of transceiver with one antenna connector to one feedline to one antenna conceptual model. One inserts a tuner/matching network in the chain, but it's still a "single thread" sort of model. And, in a single frequency at a time environment, that tuner can be quite simple (a single section L or Pi network) because it only has to "match" at a single frequency. However, in a broadband environment, you might need a more complex network (say you've got the same antenna hooked to two receivers, tuned to different frequencies). The ALE folks encounter this all the time, because on Tx, the tuner is in, and matched, which, for a physically small antenna (e.g. mobile) makes for a pretty narrow band system, so they bypass the tuner on Rx when scanning(willing to give up some power to the mismatch in exchange for broadband receive). Of course, the matching network should really be associated with the antenna (because that's what has the non-50 ohm Z.. The amp is likely broadband, as is the rx), so you'd have a network for each antenna port. I suspect that any generic solution will make some folks unhappy, unless you go to a full up crossbar matrix with lots and lots of switches and filters/networks. Consider someone who is running band specific filters to avoid interstation interference (at, e.g., field day, or a multi-multi station). Realistically, I don't think it's reasonable to include such a matrix inside a F5K (or any radio).. It's really more of a system issue. The folks at Flex made some choices to give some ability to switch things, but realistically, if you've got a moderately complex system, you need to seriously think about outboard management. It would be "nice" if the control software (either PowerSDR or a 3rd party product like HRD) accommodated such things cleanly. Think of the new breed of all-in-one remote controls for home AV systems. The old ones basically just combined your 5 separate remotes into one box, with a "mode switch". You still had to punch "Cable Box", then do the channel select, then "receiver/amp" and select "cable box audio", then "TV" and select "cable box video input", etc. The new ones hide all this from you, and you just say "watch cable", and multiple commands go out the various boxes, and things work transparently. (my Logitech harmony just failed after 2 years, and we're back to 5 remotes, and it's a royal pain). In many ways, the ham radio world is sort of at the early "all-in-one" remote stage, before "learning remotes" came out (i.e. you've got to look up the model numbers for all your various gear and enter it into HRD, or a similar program, so that it knows what protocols to use, etc.) Jim, W6RMK _______________________________________________ FlexRadio Systems Mailing List [email protected] http://mail.flex-radio.biz/mailman/listinfo/flexradio_flex-radio.biz Archives: http://www.mail-archive.com/flexradio%40flex-radio.biz/ Knowledge Base: http://kb.flex-radio.com/ Homepage: http://www.flex-radio.com/
