Useful radio features

[K7TV]

Frustrated by the weight, size. cost and wires of a KX3 + KXPA100 combo for
light 100W portable operation, I got a Yaesu FT-891 (but keeping the KX3
which is superior when 100W is not needed). Going into this I knew that the
891 has horrible phase noise, but that is of no consequence since this radio
is not for operation in town, nor in multistation contesting, where nearby
stations would be bothered by the phase noise.

 

What I got is a radio about the same size as the KX3, but putting out 100W,
with a weight of about 5 lbs, and a price under $600. Yes, it relies on
fans, but they are not very loud. The whole 100W radio is about the size of
a smallish 50W VHF FM rig. This suggests to me that Elecraft might want to
design a KXPA100 that is much smaller and lighter than the current model,
and using fans.

 

The FT-891 architecture is similar to the K3 in important respects. A
roofing filter is used in conjunction with audio frequency DSP processing
for final selectivity and noise reduction.  Many current high end rigs that
seem to have copied such elements of the K3 design, but in a cheap radio
this is not common. Performance of the FT-891 in the presence of strong
signal interference is not competitive with the K3, but it is not bad. Noise
reduction is quite good, and probably competitive with the K3 based on my
very limited testing. But the 891 has an additional tool that is very useful
for improving voice copy. They call it "Contour". I would call it a
parametric equalizer. It also reminds me of an old-time Q-multiplier. The RX
and TXequalizers of the K3 are very effective, but since they are "graphic
equalizers", it takes a while to set one up. Most of us adjust the K3
receive equalizer at most once, and never during a QSO. When I listen to
weak SSB signals in the presence of strong noise, even when using NR, on e.g
40m, it turns out that, at least with the FT-891, a very worthwhile
improvement can often be achieved by fine-tuning RX equalization. On the 891
this can be done very quickly thanks to the parametric approach to
equalization. Instead of varying a series of settings to create a response
curve point by point, we select a frequency to boost or suppress. The width
and height of the peak or valley are adjustable, but most of the time we
don't need to change those in order to make a meaningful improvement in
copyability. If the other station had optimized their TX equalizer (if they
even have one), no RX equalization on our end would be needed, but listening
at random I find most signals become easier to copy after a little RX
equalization tailored to the particular station, The notching mode, with a
moderate notch depth and width is often wide enough and shallow enough to
create pleasant voice reception by applying it somewhere inside the
passband, while deep enough to change effective passband width if applied to
the edge of the passband as a fine adjustment to the DSP bandwidth setting.
All of this is somewhat surprising to me in terms of how effective and easy
it is to use. Some reviewers of the FT-891 have claimed that with the FT-891
they can copy a station that cannot be copied on a much more expensive
radio. I have not compared side-by-side with an Elecraft radio, but it seems
to me that those reviewers are talking about something real and significant.
I am writing this to suggest that the K3 and other Elecraft radios could be
improved by adding parametric equalization to the existing array of receive
enhancement tools.

 

73,

Erik K7TV

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