W4ZV> With IF's above 30 MHz, we got General Coverage receivers at the
expense of very poor close-spaced IMD and BDR performance.
The unique DSP contribution to HF RX is smart auto-notch and noise
reduction, the rest is marketing!
IF above 15 MHz removes superhet images from HF working range! Collins IF
goes even above 3 x 30 MHz. W0IYH in QEX nicely explains cost/performance
trade-offs with narrow front-end crystal filters. I am surprised that
purists are not buying more 200 $ crystal filters at the antenna input!?
73 de Maro, S56A, N1YU
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