Bob (WB2VUF) said:
> Traditionally, that is true. Ham-band-only receivers were superior. Tuned
> circuits could be more selective because they tuned over a narrower range.
> VFO's, too, could be made more linear and stable, since usually they tuned
> only over a 0.5 MHz range. Designs are different today. Broadband front ends
> are the rule. There is no "preselector" tuning and VFO's are synthesized.
> There is no longer a big performance difference between general coverage and
> ham band equipment.
I think that depends on what you call a "big difference." The outstanding
performance of the Orion, with close in interfering signals, is largely made
possible by the narrow roofing filters ( 1KHz, 600hZ, 500Hz, 300Hz) for CW
operation (And of course excellent receiver design). Most "general coverage"
receivers use an upconversion to 45+MHz as the first conversion and then use a
VFO that allows continuous receiver coverage from 3MHz to 30 MHz. With the
upconversion to 45MHz it is not really economically possible to build a crystal
roofing filter at that frequency with a 500Hz bandwidth. Thus they have wider,
3KHz+, roofing filters and you get the poorer close in 3rd order IMD
performance of the ICOM 7800 and the Yaesu FTDX-9000.
If you don't plan to operate CW, in crowded bands, maybe not a big issue. So I
think it depends on your definition of "a big performance difference."
Merle - W0EWM
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