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Author Topic: USB-to-serial conveter for FSK RTTY  (Read 2280 times)

Posts: 388

« on: March 26, 2004, 12:38:59 PM »

Recently, I bought a new laptop for my radio station.  It is HP Pavilion 5500 series which lacks serial ports, running Windows XP.  I read in the website that you can make a Belkin F5U103 USB-to-serial converter work for FSK.  I tried MMTY with a RigBlaster and a Buxcomm interface (both FSK capable) with this converter to no avail.  I also tried a FSK file provided in the MMTY website.  No joy!!!!  The radio will key up but will not generate the FSK tones.

Has anybody been successful in using a USB-to-serial converter for FSK?  I am interested if anybody has has a breakthrough on this matter.  The radio is an Icom-746 using the ACC1 port.


73 DE Bert @ KA2UUP

Posts: 7

« Reply #1 on: March 26, 2004, 01:19:03 PM »

Your problem may not be USB-serial related at all. I am not sure about the IC-746, but my Yaesu FT-920 has a switch on the rear to toggle between AFSK and FSK. There are also menu settings for DATA-LSB and DATA-USB for everything rtty-related (mark, space, offset, etc.)

Obviously the PTT sigs are getting through. But remember, when running FSK using sound-card TNC emulation like MMTTY, it is usually the rig that is generating the Frequency Shift Keying.

Check your IC-746 manual to see if and how you must change to FSK mode, not AFSK. gl es 73 de N7XB

Posts: 340

« Reply #2 on: March 26, 2004, 01:54:32 PM »

If you read a little deeper into the help files you will find that you can't use a USB device to key the FSK jack on your transceiver. The reason is simple, a USB device can't be set at the required 45 baud rate. You need a real UART like a 16550 serial port chip for that. It will work fine for PTT control. There is a cheap way around your problem. Simply buy a cheap 386 or above Laptop with a serial port and build a cheap Hamcomm style modem for it. It will key your transceiver in FSK mode and using Hamcomm 3.1 or Terman93 software (now free) will allow you to operate in not only RTTY mode but also full linked ARQ Amtor mode. Terman93 also allows RTTY and ARQ Amtor mode, and even full FEC and ARQ Pactor I mode! Something the sound card can't do. Check this link on how to do it.
You can also use an old terminal unit for better performance check this link
I now use a Flesher Corp TU-170 Terminal unit with WF1B RTTY contest software which supports Terminal units. I did a few upgrades to the TU to improve performance. It has three stage narrow filters for each of the Mark and Space frequencys! ICOM uses a DSP version of this filter design in the IC-756 PRO line of radios known as the twin peak RTTY filter. I replaced all the older MC1458CP1 OP-Amp's with modern low noise high performance TL082 BIFET OP-Amp's. The old TU will now out perform any sound card or TNC unit on the market today. Not only that it runs in open squelch mode. If there is any kind of a Mark and Space tone in the noise the TU will demodulate it and print the text on screen.

Posts: 6252

« Reply #3 on: March 26, 2004, 02:46:32 PM »

I may be mistaken, but I believe a PC card style adapter is available that will provide the required serial port.  Of course it may be a little pricey.....

Posts: 828

« Reply #4 on: March 26, 2004, 03:23:09 PM »

 Something to remember about XP is that XP is NT. NT5.1 to be exact. And with NT, you live and die by the MS Hardware Compatibility List (HCL) which is available via the MS web site.
 In order for a vendor to have their product listed as "HCL Compliant" they must actually submit it and run a battery of tests on it. Passing the tests doesn't mean the product is faultless, but it does mean the product will perform substantially as expected, and without causing major system problems. (The odd ones can still happen, that's life.) Most NT-oldtimers won't touch a product unless it is on the list, or it is so "dumb" that it doesn't matter.

 There are only two brands of USB-serial emulators on the list, one from IBM, the others from Keyspan. Either nobody else has bothered to submit one for certificaiton testing, or everything else that has been subnmitted has been unable to pass the tests. Lack of certification doesn't mean a product is bad--it just means you have no reason to expect it is good.<G>

 USB-to-serial adapters have a bad reputation in general, probably because most of the drivers are poorly written, and some software still can't use them no matter how well they are written. On the other hand, serial ports supplied by a PC Card work 100% of the time, the ports are innately supported by the card specs. If you want to try a USB adapter, stick to one of the ones with an XP-compliant logo on the box. If you simply want one that works, robustly, with a proven track record, get a PC Card version.

Posts: 388

« Reply #5 on: March 26, 2004, 05:33:05 PM »

One thing that I forgot is that the MMTTY site has an FSK file that is supposed to work on USB-to-serial converters.  I saw that today.  I will try that and report later.  If this works, this may solve the problems for many hams.


Posts: 388

« Reply #6 on: March 29, 2004, 09:35:20 AM »

It works!!!!  And the file is not limited to any USB converter in particular when used with HamScope which uses the MMTTY engine.
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