[RTTY] [MMTTY] 75 baud RTTY with EXTFSK ...

Tue Sep 20 22:29:53 PDT 2011

/"Have you tried running FSK on the *serial* port?"/

Well there you go! I couldn't see the forest for all the trees in the 
way! I had COM1 = CAT stuck in my brain and had not given it any other 
consideration! But wait... there's even more... I think I'm on a roll... 
my docking station has three slots for PCI cards... that gives me 
another option. I guess I've broken through my brickwall and have plenty 
of experiments I can run. Thanks again for the insight.

73 de Bob - KØRC in MN
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On 9/20/2011 11:12 PM, Joe Subich, W4TV wrote:
>
> Bob,
>
>> And of course, as you pointed out, there are a variety of other
>> methods to operate at 75 baud. My contesting computer is an older
>> Dell laptop C640 with a docking station. It provides one serial and
>> one parallel port. The serial port runs the CAT and FSK / PTT run
>> from the LPT port.
>
> Have you tried running FSK on the *serial* port?  If it is a real
> serial port (and it may be if you have a true docking station instead
> of a multifunction USB adapter), it should run both 45.45 and 75
> baud with MMTTY or MMVARI using the standard drivers (serial port
> for MMTTY and FSK8250 for MMVARI).   It would be very easy to add
> a generic USB converter for CAT/CW/PTT.
>
>> These manufacturers discuss thr top speed but there is no mention of
>> the lowest speed supported. The second link refers to the MCS9835 LSI
>> device which supports 5, 6, 7, and 8 bits, which sounds promising.
>
> The MCS9835 is a MOSCHIP device that is capable of providing two
> 16C550 compatible serial ports and one parallel port depending on
> the external components.  A 16C550 compatible serial port should be
> capable of 45.45 baud operation and while the data sheet:
>      http://www.comet.bg/datasheet/Interface/9835.pdf
> does not specifically list a baud rate divisor for 45.45 baud, the
> 1.8432 MHz baud rate clock is low enough and the baud rate table
> shows a divisor of 1 for 115.2 K that 45.45 would surely be available
> with a baud rate divisor of 09E6(h) or 09E7(h) (45.46 or 45.44 baud).
> Assuming the divisor is a 12 bit number as in the 8250/16450 UART and
> FTDI USB UART, the lowest (standard) data rate would be 30 baud.
>
> > What is your opinion of finding a PCMCIA adapter that might be "slow
> > enough" to direct key FSK from MMTTY?
>
> There are plenty out there ... two port PCMCIA adapters were a common
> solution for laptops before USB became so ubiquitous.
>
> 73,
>
>    ... Joe, W4TV
>
>
>
> On 9/20/2011 10:57 PM, Robert Chudek - K0RC wrote:
>> Hello Joe,
>>
>> Thanks for the detailed technical background regarding the limitation of
>> the implementation of the EXTFSK driver. It's no secret I have been
>> vocal about the possibility of extending the capability to 75 baud.
>> Unfortunately I don't have the programming background or skill to meddle
>> with the source code.
>>
>> And of course, as you pointed out, there are a variety of other methods
>> to operate at 75 baud. My contesting computer is an older Dell laptop
>> C640 with a docking station. It provides one serial and one parallel
>> port. The serial port runs the CAT and FSK / PTT run from the LPT port.
>> This has worked fine for years. (Yes, I am waiting for Ed McMahon to
>> show up with the check, then I'll upgrade!)
>>
>> This discussion made a light bulb come on... the laptop has a pair of
>> PCMCIA ports. I see a variety of PCMCIA adapters that provide serial
>> ports. Here's a couple examples:
>>
>> *http://tinyurl.com/6ed3869*
>>
>> *http://tinyurl.com/2z2c2w*
>>
>> These manufacturers discuss thr top speed but there is no mention of the
>> lowest speed supported. The second link refers to the MCS9835 LSI device
>> which supports 5, 6, 7, and 8 bits, which sounds promising.
>>
>> What is your opinion of finding a PCMCIA adapter that might be "slow
>> enough" to direct key FSK from MMTTY?
>>
>> 73 de Bob - KØRC in MN
>> ------------------------------------------------------------------------
>>
>> On 9/20/2011 8:35 PM, Joe Subich, W4TV wrote:
>>>
>>>
>>>  From time to time I see comments that some individuals would like to
>>> see JE3HHT modify EXTFSK to support 75 baud RTTY. I have recently
>>> exchanged e-mail with Oba, JA7UDE about that possibility and Oba
>>> advises that he attempted to add 75 baud support to EXTFSK some years
>>> ago without success due to problems with bit period instability
>>> (jitter).
>>>
>>> EXTFSK uses the Windows Multimedia Timer that has a maximum resolution
>>> of 1 millisecond. However, the timer is not stable due to the nature
>>> of Windows process swapping, etc. I have measurements (scope photos)
>>> made by OM7ZZ at microHAM which show the 22 millisecond bit period
>>> from EXTFSK will vary +/- 2 ms (+/- 10%) on either a motherboard UART
>>> or USB converter (measurements made on both devices to eliminate the
>>> effects of USB latency). The instability (jitter) is due to the MM
>>> timer and thread switching in the Windows operating system.
>>>
>>> If we apply a 1 millisecond resolution and 2 millisecond jitter to 75
>>> baud, we start out at 77 baud (13 ms bit period). With 2ms jitter,
>>> the baud rate can vary from as low as 66.6 (15 ms bit duration) to as
>>> high as 91 (11 ms bit duration). A +/-15% instability in baud rate
>>> will result in significant performance issues.
>>>
>>> There are other solutions for 75 baud FSK operation with MMTTY. If you
>>> have a serial port (motherboard or add-in card) MMTTY will support it
>>> directly. If you have only USB ports, some of the better interfaces
>>> (all of the microHAM "Keyers", RigExpert Standard and Plus, Navigator
>>> by US Interface) support 45 and 75 baud operation using a UART (serial
>>> port) compatible interface, or you could use an AFSK to FSK converter
>>> like the FSKit by K4DSP in the August 2011 QST (pp 40-42).
>>>
>>> Finally, one can always use AFSK.
>>>
>>> By the way, JE3HHT has released the source code of EXTFSK to the public
>>> domain. Anyone is free to add 75 baud support if they wish. There are
>>> additional timers with better resolution in Windows 2000 and later. It
>>> would not be at all inconceivable for a dedicated programmer who was
>>> willing to do the research and work to use the same basic approach with
>>> a different timer to add 75 and 110 baud support to EXTFSK if they
>>> wanted to do so. The source code is part of EXTFSK106.zip available
>>> from www.hamsoft.ca ... have at it boys!.
>>>
>>> 73,
>>>
>>> ... Joe, W4TV
>>>
>
>