From: wvanhorn@magnus.acs.ohio-state.edu (William E Van Horne)
Subject: Re: Any other W9RG DSP Filter users on the Net ?
Organization: The Ohio State University
Date: Sun, 24 Jan 1993 14:47:44 GMT

In article <9301201443.utk24379@FAB8.intel.com> RHAREL@FAB8.INTel.COM (RICHARD HAREL) writes:
>I'm in the middle of building the W9RG DSP filter and would
>like to correspond with others on the net who have built the unit
>who can offer any input that would help optimize it's performance.
>73,
>Rich
>WB2JBS
>rharel@fab8%sc.intel.com


To: Rich - WB2JBS
From: Van - W8UOF

After building the W9GR DSP system, I will pass on my observations for
whatever they may be worth.  Perhaps you noticed the posting made by my
son, Bill Van Horne, on this same subject.  I agree with his observa-
tions.

I found the kit quite complete and the instructions very adequate.  I
might add that I have never before built a kit on a printed circuit
board, although about 15 years ago I built a large display digital clock
using wire-wrapping techniques and TTL chips.  That was the only other
electronic construction I had done since vacuum tube days before tackling
this project.

I had no problems with soldering, but was extra careful to use a bare
minimum of solder on each connection.  I inspected each under a magnifier
before going to the next.

I have the following specific suggestions:

     1.  Contrary to previous postings, I did not find the power
     excessive for a Radio Shack wall-plug type 500 ma. 12v. power
     supply.  I did use an extra 4700 mfd filter capacitor across
     the input terminals.

     2.  I used the larger size, steel, cabinet available from Radio
     Shack, rather than the one recommended because the latter was
     too confining for my taste.  My cabinet is 6" x 8" x 3".

     3.  The only real problem I had was mounting the LED bar display
     on the front panel.  The suggested way of bending the legs of
     the supplied socket was a disaster, and I can't see that it
     would ever be anything but a terrible kluge.  I made a sub-chassis
     out of a small piece of perf board with 0.1" perforations.  The
     leads from the display exactly fit the holes.  After putting the
     display chip on the perf board, the leads barely project through
     the under side, but are long enough to allow one to wire-wrap or
     solder onto them using fine wire.  (I used #30 teflon wire-wrap
     type).  I twisted the ten pairs of wires together into a kind
     of cable and soldered them into the holes in the main p.c. board.
     Then I mounted the sub-chassis behind the front panel on 1/4"
     spacers.  That way, its front surface is flush with the front
     panel through a rectangular hole that I cut with a nibbler tool.

     This was not the neatest way of doing the job.  A friend who also
     built one of these did a better job: he mounted a standard DIP
     socket in the holes on the p.c. board, then made up a 20-pin header
     with a length of 20-conductor computer type flat cable to run to the
     LED's which he mounted on the front panel.  That is doing it the
     right way, but mine worked ok.

     4.  I found the indicator lights and especially the LED bars too
     bright.  Instead of 330 ohm load resistors on each LED, a value
     of about 1000 ohms would be better.  My friend mentioned in the
     paragraph above found the same and suggested the solution to me.

     5.  In the main instruction booklet, W9GR passed on two suggestions
     offered by other users to reduce some 10 khz. feed-through that is
     annoying in hi-fi headsets.  I discovered the same thing, and made
     the suggested modifications.  I am not sure, however, that they
     are worth the trouble.  Also they involve cutting traces on the
     p.c. board, and other delicate operations that most builders will
     want to avoid.

     6.  My only criticism of the design is the clumsy method of
     switching operating modes.  Others have commented about this, and
     I agree with their criticisms.  I am sure future models will
     incorporate improvements.
     
     The end result is everything I had been led to expect, and then
some!  The effect of the noise cancellation on a marginal SSB signal is
quite striking.  My son's posting said it was like the quieting one
hears when he tunes in an FM signal.  I agree that it can be almost that
dramatic.  Others have noted that DSP is not magic and it will not
magically drag an unreadable signal up out of the noise and make it
hi-fi.  That is true, but it is also true that many signals that are
fading in and out of the noise so that only 50 percent of the words are
understandable can be boosted to maybe 70-80 percent and that can make
a difference between a reasonably satisfactory and a totally unsatis-
factory QSO.

     My main interest is CW and digital modes.  I use the narrow
filters in cascade with the 500 khz. i.f. filters in my Kenwood TS940
on both CW and AMTOR.  The idea that filters can be that narrow (down
to 70 herz!) and still not ring is mind-boggling to me.

     W9GR has done a real service to the ham community in my opinion,
and I will use this medium to thank him for it.

Good luck, and 73, Van - W8UOF
wvanhorn@magnus.acs.ohio-state.edu