I agree that discussion of the general concept of direct conversion and SDR is
relevant to this reflector regardless of brand. At some point, all radios will
be of this design because it will be the cheapest possible way to produce a
radio.
I have not used the 7300, likely will not. I’d prefer an Omni 6+ that has SSB
audio I can tolerate, a notch filter INSIDE the AGC loop and a standalone
bandscope.
The topic of digitization at this level was discussed ad-nauseum back in 1983
and 1984 as Compact Disk technology was just beginning as a “replacement for
Vinyl records”. Things did not quite work out because the number of bits in the
audio samples and the sampling frequency (44.1 KHz) required compromises that
people with musical ears could easily hear.
The move towards direct digital conversion and SDR is a replay of the same
thing. If you don’t use enough bits in the sampling process, and don’t sample
often enough, there is not sufficient dynamic range to allow for the wide
variations in signal strength experienced on HF.
Most good operators can copy signals that are within a few dB of the noise
floor, especially in CW. These signals can easily be S1 or less on most good
receivers, depending on band noise.
The strongest signals (particularly in Europe with the big shortwave stations)
can easily be 100 dB over S9 (48 dB) for a total signal dynamic range of 148
dB. 16 bit sampling only allows for 96 dB dynamic range. In order to get 148 dB
dynamic range (3 dB dynamic range improvement per bit) you would need 32 bits
minimum to handle the range.
Keep in mind that, even though you are not LISTENING to that 100 dB over S9
shortwave station, the receiver is still seeing it as this is part of the
spectrum that the DSP is trying to unravel to select your signal of choice.
When the input to a digital device exceeds its dynamic range, the results are
far from linear so artifacts, not really unlike severe overload in analog
circuits, are heard, but often to a far worse degree than with analog systems.
By analogy, the simple harmonic distortion produced in Vinyl by overdriving the
cutting lathe were far more tolerable to the listener than the nasty aliasing
that occurred from under sampling of audio signals in early CD recordings and
the non-harmonic distortion that arose from the steps of quantization error
with only 16 bit amplitude range, especially on soft notes whose bit level
resolution was maybe two or three bits.
As manufacturers learn this (Ten Tec included) things will get better, so long
as the focus is on worst case receive scenarios. More bit depth and faster
sampling rates will improve direct digital receivers to a point that they will
be better than their analog counterparts. The marketplace will, however,
dictate when that occurs.
24 bit 96 KHz sampled audio has been available technically for 15 or 20 years
using the DVD platform, but I have yet to see a disk that can offer it even to
my damaged hearing. The marketplace preferred iPod(YUCK!) and MP3 (double
YUCK!) because you could put 2000 “songs” onto a chip the size of a grain of
rice, 100% of the songs being unlistenable sonically. Quantity wins out over
quality for most people, especially if it’s cheap.
Accepting a product with the obvious failings of poorly implemented direct
detection creates a market for the junk (translation - entry level) and delays
introduction of top performance designs.
PS: I don’t want to have to have a PC running just to sit and listen to 20
meters or to see a full scan of the band while I am doing something else. The
only reason I don’t have an Eagle today is that getting a bandscope on it is a
big PITA and I still need to have the PC running to use one.
It will be a long time before TenTec or anyone else will offer a top
performing fully digital receiver, with knobs and stand alone, so long as a
trinket market exists for the performance level offered in the 7300.
Gary
W0DVN
PPS: There is still no digital camera anywhere with the color depth to match
old fashioned Kodachrome 64. 8 bits per color? Not enough! Same cause, same
result.
>
> I am wondering about the same sorts of things. I bought a new Omni VII
> during the Fire Sale. I got it with the optional 300 Hz CW filter. Once the
> novelty wore off, I started getting annoyed by having to push a menu button,
> then scroll to a setting, and then select something like the setting the
> keyer speed, and do some other actions, just to do what a lowly knob does on
> my Corsair II and my MFJ keyer. So, that radio has found a new home. The
> Argonaut VI has a complex system of making adjustments, too, but it is much
> easier to use than the Omni VII, and seems to have a better receiver. I am
> using the Corsair II on HF again, and am starting to see why those people who
> also own one, or have an Omni VI, prefer them to the newer rigs. This was
> brought home to me rather abruptly with the recent threads on keeping Orion
> II rigs functional. With a rather obstructed trap vertical installed on a
> hillside, I am not going to set the contesting world on fire no matter what
> radio or radios I use. So, I can still prefer high performance radios that
> are getting on in years, like me, and are much less complex to use.
>
> Your Mileage will Most Certainly Vary...
>
>
> Steve WA9JML
>
>
> On 8/15/2016 1:16 PM, Mike Bryce wrote:
>> I have a hard time handling over $1500 for a radio and being told it’s
>> ‘entry level.’ Nothing like scaring the bejesus out of a new ham who after
>> spending all that money for a rig, he/she ends up with ‘entry level’ radio.
>>
>> Does one really need a $4k/$5k radio to have fun with?
>>
>> How in the world did you guys survive contesting using the Triton IVs, the
>> TS-520s, the FT-101s, and the HW-101s?
>>
>>
>> Mike WB8VGE
>>
>>
>>
>>
>>
>>
>>
>>
>
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