From: kawai@csli.stanford.edu (goh kawai - n6uok)
Subject: Re: DSP and The Future
Organization: speech research program, sri international
Date: Fri, 22 Jan 1993 18:36:15 GMT

Bill VanHorne (wvhorn@magnus.acs.ohio-state.edu) comments:

  | I spent part of last Saturday playing with ... W9GR's DSP box (described
  | in Sept. QST).  I'm impressed. ... With this $150 "toy" intercepting the
  | audio, I had no need for notch filters, noise blankers, attenuators,
  | PBT, slope tuning, or any of those high-priced goodies ...

Thanks for the review.  I had thought the particular DSP box you used was
not that great, especially since I understand it takes the audio output of
the transceiver, not any of the IF outputs.  Your review is tempting me to
try out the box.

  | Given the *current* state of DSP technology, why do we need all those
  | reception aids?  Why do we need multiple IF stages with filtering?  For
  | that matter, why the heck do we even need to continue to use super-het
  | receivers at all?  Couldn't we simply go to direct conversion with DSP
  | processed audio?  If we can, why are we still paying $2000-$3000 for
  | transceivers with all that expensive super-het stuff tacked on?  Why
  | haven't the manufacturers started producing cheaper receivers with DSP
  | working on the audio?

There are at least three factors here that affect HF receiver design.  Other
people may point out more.  The factors I know about are:

(1) Currently, much higher front-end sensitivity is available using analog
    cicuitry.  Direct digital conversion of radio waves is not sensitive
    enough for practical purposes.  So even if you elect to use DSP for the
    later stages, the front-end will have to remain analog.  Keep in mind
    this is for HF receivers, where substantial dynamic range is required.

(2) Lack of digital technology among amateur radio equipment manufacturers.
    This may surprise you, but sadly, it is true, at least for Japanese
    manufacturers that specialize in amateur radio gear, such as Kenwood,
    Icom, and Yaesu.  Their engineers are extremely knowledgeable about
    analog equipment, but lack hands-on experience in digital circuitry.
    This doesn't mean they don't know digital theory.  In fact, many
    engineers are becoming frustrated -- for instance, when Kenwood
    designed their DSP unit, they had to work with a low-performance chip
    due to cost reasons, and they were quite upset.  Wait a few years, and
    you should see gradual improvement.

    There is a definite trend of technology transfer from commercial
    equipment to amateur gear.  Japan Radio Corp (JRC), which does not have
    a strong presence in amateur radio but is extremely prominent in
    commercial radios -- for HF, maritime radios in particular -- uses
    advanced DSP circuitry which is far more advanced than what you find
    in amateur radio equipment.  This technology will eventually trickle
    down to amateur equipment.  But don't count on JRC doing that (smile).

(3) Amateur radio equipment does not sell in large quantities, and end-users
    are not willing to part with large sums of money.  Therefore,
    manufacturers hesitate to invest in large-scale development of novel
    technology.  Each manufacturer will probably sell less than 5,000 units
    of their flagship HF transceivers during their product lifetimes.  This
    accounts for the high profit margin on top-of-the-line rigs -- almost 50
    percent is profit, which will be invested in developing the next
    generation of transceivers.  Re-tooling factories and service centers to
    accomodate new technology (not necessarily digital) is expensive, and
    may require more funds than is available to the company.  Therefore,
    product improvements will be incremental in nature, and in all
    likelihood will lag commercial technology.

-goh-

----------------- Speech Research Program, SRI, Menlo Park, CA 94025-3493 USA
--- Goh Kawai --- work:(415)859-2231   fax:(415)859-5984   home:(415)323-7214
----------------- internet: kawai@speech.sri.com      radio: n6uok and 7l1fqe
Newsgroups: rec.radio.amateur.misc