You look at the TS-870, 746pro, and many other DSP rigs all make the same stupid design flaw. Dual conversion DSP! No multiple pole xtal filter. No computer algorythm can emulate a multipe pole IF filter. These are your $2000-$3000 rigs The TS-850 had dual xtal IFs. However there was much junk from all the CPU's and yes up conversion, then downconversion and demod after the 2nd IF filter adds to the noise floor. How the R-7A did it was interesting. A 4 pole Fixed Xtal filter followed the upconverter. It has a pass band of 12kcs. That's right a 12Khz wide IF. This gives this collectors radio its used price tag of $2000. The 2nd IF used those 8 pole can filters. I found the K-2 has crystal clear SSB with the 1.8khz filter position. The R-7A the SSB gets muffled at 1.8khz. I use 1.8 khz only on the K2. The TR-7 used a 2 pole filter after up conversion. If you look at the schematic of the TS-850, you see the dual IFs are in the back of the receiver. So after upconversion the passband is 50kc wide. That is a large window for synth junk to get in. HOWEVER IF YOU USE CW filters in both IFs, your CW reception will be as good as a K2 The K2 wisely put much non xtal filtering right after the antenna jack. The band pass filters are wide enough for the Ham bands and very little general coverage. You lose general coverage ability of an R-7A. However do you really need a short wave rcvr in a ham rig? So yes one can compare the K2 with up to $3000 dollar rigs. However on SSB TX the K2 comes up average. It is average because the SSB adapter is a simple design. The all important audio chain is mostly in 2 chips. However I always get good audio reports. A RF proc of the TS-850's design would make the K2 rock. There is a cheap way of doing this. There are a few speech procs that go between the mic and rig. They are true RF procs. Your audio is up converted to 500kc. The 500Kc RF is processed by using an AGC like amp. At the RFstage more compression can be used with out AUDIO DISTORTION. Any RF clipping by products are filtered out. The DSB signal is then down converted back to audio with the exact same phase it entered the device. So one is feeding in audio that was RF processed. One can use up to 12db of RF processing. Audio processing gets distorted after 6db. One company makes this device for $60. It can be put in the mic or in the rig. I am ordering one. I will give on air checks for those that want too. _______________________________________________ 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
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