[JRC] (More) Construction of RS-232 board for NRD-525

[Philip Atchley]

Hello, it's me again.
After extensively studying the schematic of the CMH-532 board I have come to
the conclusion that it is entirely feasable to build one of these, or at
least a board that is functionally identical electrically.   All the chips
appear to be common garden variety chips (though it is getting more
difficult to obtain DIP chips, everything's going smt).

The  present plan entails building the basic circuit on R/S Universal IC
circuit cards (one or two sandwiched as needed) and replacing the DC/DC
converter with either a commercial -12VDC DC/DC converter chip or a "charge
pump".  To help with this planning task I've contacted my brother who is
much stronger in "Digital" than I am (my specialty is RF and analog).   The
DC/DC converter is the sticky wicket as all the digi stuff is more or less
routine  circuits.

Depending on what it costs to get that -12VDC I suspect the cost of
components may well be under $50.00, especially as I have some of the needed
parts in my junkbox.  But even if a person bought everything new it would be
WELL under the 300.00 or so I've been told these units often sell for!!!

NOW, I need information from anyone who can help me.  The owners manual
doesn't give any particulars on BAUD RATE or what commands the NRD-525
expects over the RS-232 cable, though I expect I could use any of the
control progrms that are already out there for the radio (including my
Fineware Shortwave database program).

QUESTIONS:
1.  What is the physical size of the card (in case I wish to later add a
rtty card)?
2.  What is the BAUD rate to the computer?
3.  What commands are read to and from the radio?
4.  What is the "connector type" to the I/O Data Card (looks like just an
inline header at first glance)?
5.  Does the RS-232 cable that exits from the card go directly to the rear
panel connector or is there another place this cable terminates?
6.  What is the Type of rear panel connector (DB-9 ?).

I expect it will probably be a "work in progress" for the next couple months
but when I finally get a working sample I'll try to post the schematic,
construction information etc for anyone who may want to build one.  It will
be labor intensive as it will be "point to point" wired on the universal
circuit card.  I DON'T intend to make a PC board.


73 de Phil  KO6BB

*****************************************************
*  Chasing NDB's (Non-Directional Beacons)with ...  *
*  RECEIVER 1: JRC NRD-525 W/500Hz CW filter.       *
*  RECEIVER 2: Homebrew Longwave CW receiver.       *
*  AUDIO FILTERS: Datong FL-3, Heathkit HD-1418.    *
*  ANTENNA: Loaded 20 Meter Long Sloper.            *
*  50dB Gain Low Noise Tunable Preamp.              *
*  LOCATION: Merced, Central California.            *
*  COORDINATES: 37.18N  120.29W  CM97sh.            *
*****************************************************