In a message dated 8/11/06 7:18:34 AM Eastern Daylight Time, [EMAIL PROTECTED] writes:
> There is an alternative to the usual type of single down conversion and > double (up - down) conversion receiver, which is a single up-conversion > receiver using a lowish VHF IF and detector. Can really good CW filters be made for VHF? By "really good", I mean, say, 400 Hz bandwidth, less than 6 dB loss, 6:60 dB shape factor less than 3 to 1? What about stability over the temperature range? The benefits of up-conversion > > are then available from a relatively simple architecture. The only real advantage I see is a small reduction in spurious responses, caused by being able to have the low-order spurs be way up in the VHF, and those which are HF become quite high-order. A secondary advantage is GC receive. Certainly the cost > > of good narrowband VHF filters remains, but it is offset to a large extent > by the removal of a second IF and its filters. Who knows, the cost of good > VHF filters could well come down if more were used. > How much more do VHF filters cost? Note that if you can live without IF shift, or if you implement IF shift by different means such as simultaneously pulling the BFO and LO in equal but opposite amounts, the single-IF approach of the K2 leaves little to be desired. Perhaps the big question is this: Could a rig as good or better than the K2 be implemented using a different architecture *without* a serious increase in price or power drain, without losing the "user build- and service-ability" of that rig? 73 de Jim, N2EY _______________________________________________ Elecraft mailing list Post to: Elecraft@mailman.qth.net You must be a subscriber to post to the list. Subscriber Info (Addr. Change, sub, unsub etc.): http://mailman.qth.net/mailman/listinfo/elecraft Help: http://mailman.qth.net/subscribers.htm Elecraft web page: http://www.elecraft.com
