leowood2...@msn.com schrieb:

Some points I can think of offhand:
* Use good quality IF filters, i.e. 6-element ceramics or such for AM.
  (If these should not be available, get inventive.) I'd combine these
  with a wider tail filter. I guess DSP usage is not an option? Some
  care when applying the 1st IF crystal filters may not hurt, to ensure
  good image rejection (as well as intermodulation characteristics). FM
  should use 3 cascaded filters with a medium bandwidth to match the
  Satellit 700, with 3 gangs (tuned front-end circuits) recommended.
* With a two way speaker system, make sure sound is as good as possible
  with the concept, and that not only to Chinese ears. Audio engineering
  has sadly been frequently neglected in the last 10...15 years or so.
  If some kind of EQ circuit (for speaker operation only) is needed, so
  be it, the radio makers of yore also used such tricks. (There should
  be an additional tone control, tastes in sound differ after all.) Some
  research in terms of vibration suppression or loudspeaker building in
  general and such may be of help. Given the sound is right, a simple
  line-level 3.5 mm (stereo) input for amplifying purposes might be a
  nice touch.
* Get the internal shielding right, particularly with a non-negligible
  digital section.
* Oscillator pulling by lighting LEDs (DE1102 in SSB) and other such
  funky stuff better be ironed out, along with operating kinks. Plain
  ol' analog volume control and paged decimal presets please.
* Front end selectivity for the AM ranges should be one filter for LW,
  one for MW and then several (~ octave) for shortwave, maybe further
  varactor-tuned. (The '700 had an electronically tuned preselector,
  though it seems alignment of the thing from the factory wasn't always
  that great.) Those living near MW transmitters (rather common in the
  US) are likely to appreciate a highpass filter for shortwave.
* A big receiver should offer sufficient space for a big ferrite rod
  antenna, for good LW/MW (and I'd also suggest low SW up to ~2.5 MHz or
  so, where telescopic antennas tend to be inefficient) sensitivity and
  directionality. Something rotatable à la RF-2200 might be worth
  considering; the bigger a receiver is, the more tiresome rotating the
  whole thing becomes.
* I suggest at least two different frequency steps, better 3 - usual
  frequency grid for the band, 1 kHz and then something smallish (maybe
  100 Hz plus analog fine tuning, or <= 20 Hz without).
* Memory presets: With EEPROMs being rather inexpensive these days, a
  few hundreds with at least 8-digit name tags should be possible. But
  if MP3 recorder functionality (with commodity flash memory, I guess?)
  is already present, one could also use the associated storage. If this
  should be removable, a simple file format like CSV could enable easy
  presets interchanging and PC based updating. (This might even include
  firmware updates, which certainly are not a bad idea.) The MP3
  recording probably features adjustable sample rates, (average /
  variable, not only constant) bit rates and mono/stereo selection?
  (Shortwave recordings would probably require no more than 11025 Hz
  mono and thus a relatively low data rate, while FM stereo would best
  be recorded with 32000 Hz or 44100 Hz in stereo.)
* In spite of all possible complexity, the essential functions - tuning
  and frequency entering, tone control, basic preset saving and
  recalling - must remain simple and intuitive to use. If someone can
  figure these out without reading the manual, this is good. On a bigger
  set, placement of things like a tuning wheel requires some thought in
  order to avoid (arm related) fatigue during longer listening sessions.
* Any plans for DRM reception? (Provided some matching and not so power
  hungry ICs are already available. If not, a 12 kHz IF output derived
  from a suitable spot - maybe behind a 10...12 kHz filter normally
  improving ultimate rejection - is better than nothing. Reserving some
  space for an add-on DRM board may not hurt then.) What about RDS for
  FM?
* Dual balanced 1st mixers have been very similar in portables, and
  that for over 20 years now - how boring. Try some other circuit
  variants, maybe these give better results.
* For a receiver of this class, availability of servicing instructions
  is virtually a must.

I'm pretty sure build quality will not be an issue, given I see little
reason to complain about this even on the little DE105 (I recently
obtained a relabeled one). DEGEN certainly has the potential to become a
major player in the mobile entertainment market.

Stephan
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