On 7/25/2014 11:26 AM, Ron Notarius W3WN wrote:
Of course, what is the “best” radio is a very subjective thing these days.
Size, shape, other ergonomics, manufacturer/brand loyalty, filter selection... all are
factors.
#1 -- the ability of the RX to reject very strong signals
#2 -- ergonomics, reliability, familiarity
#3 -- I have it, or the place where I want to operate has it, or I can
borrow it
As to filters -- In modern radios, IF filters are done in DSP, and can
be set to any bandwidths and shapes that are provided by the firmware.
The K3 and KX3 can be set for any IF bandwidth between 100 Hz and 4 kHz
in 100 Hz steps, and can be shifted in 100 Hz steps. The K3 allows for
additional hardware plug-in crystal filters, but these are ROOFING
filters whose primary function is to protect the DSP IF from overload by
strong signals outside the selected IF bandwidth. You don't have to buy
a 400 Hz filter to get 400 Hz bandwidth, you just turn the front panel
knob to 400 Hz, and if you want 250 Hz, you turn the knob to 250 Hz.
Of course, like any signal path, a roofing filter will cascade with
other filters in the path (the IF filter) when their bandwidths are
nearly equal to provide steep slopes and deeper rejection of
off-frequency signals.
My K3s have 8-pole 2.8 kHz filters for TX which serves as the "wide"
roofing filter, and I've added a 1.8 kHz for SSB, and 400 Hz and 250 Hz
roofers for CW and RTTY. All are 8-pole filters. FWIW, I find the 1.8
kHz filter too narrow for SSB, and like the 2kHz filter better.
If you're not a contester, you need only the stock 2.7 kHz 5-pole or
extra cost 2.8 kHz 8-pole filter.
Note that I'm describing what the K3 and KX3 do because those are the
DSP radios I know, but the concept applies to other DSP radios.
There are at least three major reasons Flex radios have not "caught on"
among contesters. #1 is the strong signal problem, -- what Rob called
the Field Day problem. #2 is user interface when you're contesting, you
want knobs so you can do several things quickly. A mouse doesn't cut it,
both because it isn't fast enough, and also because you're doing
computer logging. #3 is the other half of the Field Day problem -- many
are pretty dirty on TX.
Think about this -- the Eagle, K3, KX3, and the Flex radios are all
SDRs. The K3 and KX3 have knobs, the Flex radios do not. The K3 and KX3
have superior strong signal performance, the Flex radios do not. Don't
know about the Eagle. Only a few (count on one hand and have fingers
left over) radios in the $10K range are as good, or nearly as good, as
the K3 and KX3 for strong signals. The K3 is super clean on TX, the KX3
and Flex radios are not. Some of those $10K radios are cleaner than
others on TX.
73, Jim K9YC
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