sprint/2 radios

N0bsh at aol.com N0bsh at aol.com
Fri Jul 29 00:35:36 EDT 1994

I too have been looking over the Sprint results (finally got my NCJ!!)

Here's something I don't recall any recent discussion on (in NCJ or here -
only been on reflector 2 months):

It appears that about half of the top ten used two radios and half
didn't.  Is there a **significant** advantage in using two radios in the
sprint and if so what is it?  Late mults on 20?  Early mults on 80?  Casual
sprinters early/late?  I just don't see a strong correlation between # of
radios and # of Qs.

I've never used two radios in a sprint but I'm considering trying it in
September.  MAYBE it will help me finally break 300!  (guess it wouldn't hurt
to do these more than once every two years though)

73,  Mike  N0BSH
n0bsh at aol.com

>From raid5!davep at csn.org (Dave Palmer)  Fri Jul 29 04:44:09 1994
From: raid5!davep at csn.org (Dave Palmer) (Dave Palmer)
Date: Thu, 28 Jul 1994 21:44:09 -0600 (MDT)
Subject: Use of opto isolator for CW keying
Message-ID: <9407290344.AA02164 at raid5>

Here's a circuit I use to interface my IBM PC compatible laptop's
printer port to the CW keying line of my HF rigs.  I mentioned it on
the Reflector the other day, and Walt, K2WK, and Peter, N4ZR were
interested in the details.  Thinking there may be others who might
find it useful, here it is.

The CW sending program I use is a C++ creation of John Best, KJ6K. It
permits the toggling of the output bit of your choice.  The parallel
printer port data bits are a good choice because they can usually drive
a moderate amount of current, and because the serial port is often
used for other things during a contest.  I had been driving the TenTec
keying line directly from a printer port data bit, but this didn't work
with the Icom 735. (In fact, the Icom damaged the printer port bit.
This may not be a widespread problem because the port I am using is
on an IBM PC Convertible (laptop) which may lack the same amount of
drive capability found on a desktop PC).  It looked like a circuit with
an opto isolator was in order.

 LPT1                        ________________         o----Icom key line
 ------    +5v    220ohm     |(A)           |        /
      |---------/\/\/\/\-----|Pin 1   Pin 5 |-------o   S1A
      |                      |          (C) |         o----TenTec Key line
      |----------------------|Pin 2         |
      | DB25 Pin 5           |(K)           |         o-----Icom ground
      | (data bit 3)         |          (E) |        /
      |                      |         Pin 4|-------o   S1B
 -----                       |______________|_        o-----TenTec Ground

 1.  Data bits 0 through 7 are on DB25 pins 2 through 9 on a PC parallel
 2.  The optoisolator is an ECG 3041 or Radio Shack TIL-113 or similar.
 3.  Pins 1 and 2 are the LED, and you need a source of +5 volts, dropped
     by the 220-330 ohm resistor attached to pin 1.  (I put the resistor
     inside the PC, and cut one of the other data bits, and used that data
     bit's DB25 pin to send the power out to the optoisolator).
 4.  Switch S1 is a DPDT switch and ensures that you key one and only
     one transmitter at a time.
 5.  I constructed the circuit inside the small Radio Shack experimenters
     box, part number 270-283, because it also comes with a piece of
     perf board on which to mount everything (and because there was one
     in the junk box).
 6.  The Morse program will need to write a "0" to the selected printer
     data bit in order to key the transmitter. Check the documentation
     for your software to make sure that is what the program expects.
     (For my program, I configure the port to use the "inverted" option).

If you want to key the radio with an RS-232 handshaking line, you might
use the similar circuit which is described in the documentation for the
SuperMorse program by Lee Murrah, WD5CID.

If you are really going into two-radio contesting mode big time, you
should see the article by Tim Duffy, K3LR, in the September/October 1988
issue of NCJ on page 9 titled "A Two Radio Switching System".  Tim's
circuit includes provisions for switching receive audio and PTT lines as
well (but doesn't include the optoisolator).

Hope that was worth the bandwidth!   I'm not sure what commercial logging
and Morse programs recommend for CW keying since I use a homebrew logging
program, so this post may be redundant to some of you.  But this circuit
solved my problem of insufficient drive.  In other cases, it may also help
to eliminate ground loops and provide greater RF immunity, thus reducing
keying "lock up".

Cheers and 73,
Dave Palmer, N6KL
davep at arraytech.com

More information about the CQ-Contest mailing list