A friend of mine loaned me a K2 for a couple of weeks. I spent considerable
time listening to it and IMHO, it does not fit into the same category for
quietness as the R2, Triton, 1340, Conar etc. In fact, it reminded me more
of something like a Corsair. QRN on 80m came through as a hefty roar.
As for old boatanchors like HROs etc. George is right. They weren't very
quiet. I've got a beautiful HQ-150 which holds the record for maximum number
of knobs, 21. 2 RF amps, 3 IF amps, gain , gain, gain! Then after all that
gain we have a crystal filter and Qmultiplier. By now, the guy on the other
end has gone to bed.
Now as for this DSP business. DSP certainly adds some versatility but we
shouldn't use it help mask a noisy RF chain. The TS-870, as good as it is,
has several extra mixers which provide IF "slope tuning" which acts as the
"roofing filter" prior to the DSP. Although it doesn't use those narrow,
ringing, xtal filters, it still requires those extra mixers to do the slope
trick. In cw mode, adjusting the DSP filter also activates the IF mixers to
overlap two IF frequencies and produce a narrow bandpass. Of course this
protects the DSP from being overwhelmed with strong signals. I assume the
ICOM PRO works in a similar manner?
Steve Ellington N4LQ.
> Stuart, this noise discussion takes me back to the days of my National
> HRO-5TA1. Single conversion and no roofing filters. Wonderful old radio -
> for its time. It was 1947 if I remember when I got it, but the design
dates
> back to 1937 or 38 when it was first introduced.
> Its forte' was extreme sensitivity coupled with a high-performance crystal
> filter for single-signal selectivity. Mine even has a "noise limiter" on
> it!
|