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Author Topic: USB CW interface question  (Read 1460 times)
AF5CC
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Posts: 834




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« on: March 19, 2013, 07:00:11 AM »

Is there a simple, inexpensive interface to go between a USB port and the CW jack on a radio to allow contest logging programs like N1MM and NA to be used as a memory keyer?

John AF5CC
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NR4C
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« Reply #1 on: March 19, 2013, 07:28:40 AM »

Yes.....

you will need a 1K resistor and a 2N2222 transistor.  On the 9 pin RS-232 connector, Pin 5 is grnd, Pin 7 is RTS and Pin 4 is DTR.

Now, the resistor goes between either RTS or DTR (dependig which you want to use for CW keying) and the BASE of the transistor.  The COLLECTOR goes to the KEY jack on your radio, and the EMITTER connects to the SHIELD of the KEY cable, and also to PIN 5 (GND) of the 9 Pin connector.

The web site http://www.aa5au.com/rttyinterface.html has more information on this including schematic and how to setup for PTT and also FSK.

...bill  nr4c
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AA4PB
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« Reply #2 on: March 19, 2013, 08:09:36 AM »

Since you said "USB", you'll also need a USB-Serial converter cable and the appropriate virtual com port driver for your operating system.
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K5LXP
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« Reply #3 on: March 19, 2013, 09:26:18 AM »

Winkeyers are almost universally supported by logging programs these days and is a better way to go than a big-banged serial port.

http://k1el.tripod.com/wkusb.html


Mark K5LXP
Albuquerque, NM
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NR4C
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« Reply #4 on: March 19, 2013, 10:34:04 AM »

AA4PB, thanks for adding that little detail!  When he said USB, I assumed (bad practice) that he meant "USB>SERIAL" adapter.

Now, if some aspiring ham woutld combine a FTDI chip, and the transistor switches on a small circuit board with appropriate cabling, that would be neat.

I do realize the WINKEYER USB will provide the CW action, but it costs a lot more that the simple switch that will fit inside the D-Sub shell (which is the most expenseve part of the project) and will also work for PTT and also FSK (which the WINKEY USB won't do).

...bill  nr4c
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K5LXP
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« Reply #5 on: March 19, 2013, 07:16:26 PM »

  if some aspiring ham woutld combine a FTDI chip, and the transistor switches on a small circuit board with appropriate cabling, that would be neat.

You just described a winkeyer.  It even uses an FTDI interface.  You can't bit bang one of those though.

Quote
the WINKEYER USB will provide the CW action, but it costs a lot more that the simple switch

No question about that.

Quote
also work for PTT and also FSK (which the WINKEY USB won't do).

It will absolutely do PTT, as well as work as a standalone keyer with memories.  I'm not sure what you'd use CW FSK for (you mean MCW?).

If it's a desktop PC with a PCI bus, "real" serial cards are inexpensively available that would allow real bit banging.


Mark K5LXP
Albuquerque, NM
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K2DC
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« Reply #6 on: March 20, 2013, 03:14:22 AM »

Another option (which I may soon be doing) is to add a serial card to the computer.  I found one with 2 ports for $17 shipped.  Then just follow NR4C's trick.

73,

Don, K2DC

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AA4PB
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« Reply #7 on: March 20, 2013, 05:21:54 AM »

With WinKeyer, the computer sends ascii characters to the WinKeyer. The WinKeyer then converts them to Morse and toggles the key input on the transmitter to send the CW. That's quite different than the older method of having the Morse generated by the computer and toggling a control pin on an RS-232 serial port to directly key the transmitter via a transistor. The advantage of the WinKeyer is that the Morse timing is generated by the WinKeyer chip and is not dependent on the timing of the multitasking Windows operating system. I expect that timing jitter could be even more of a problem when using a USB connection than it is with the legacy RS-232 serial port. Trying to key an FSK input with USB may even present a worse problem.

If you use WinKeyer I assume that you will need to be sure that the software is designed to support WinKeyer. Even though WinKeyer uses a virtual serial port on the computer, it expects to see serial ascii characters on the data line rather than the "toggling" of a control signal.
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WA3SKN
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« Reply #8 on: March 22, 2013, 06:20:01 AM »

I don't know about simple.  The USB is really a packet linkup with a transmit and receive pair, it is not like a RS232 serial interface that could easily be used for on-off keying.
It CAN be used, though.
73s.

-Mike.
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AA4PB
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« Reply #9 on: March 22, 2013, 07:26:07 AM »

It's all a matter of how much timing jitter (error) you can tolorate. On my computer here with no applications running there are 57 processes running just to support Windows. The processor can't run all those simultaniously, it has to be shared among them by running each in a time slice. If I write an application, Windows OS decides when my code will be run. I can't count on it necessarily being available at the exact time that I need it - thus the potential for timing errors in a real-time application like keying a CW or FSK line. The larger the number of processes running the larger the error and the faster the processor the smaller the error. Adding USB to the mix increases the delay and potential timing error.


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