On Feb 8, 2013, at 10:01 AM, ham@n0sq.us wrote:
> Already tried reversing the polarity.
>
> Joe Subich, W4TV <lists@subich.com> wrote ..
>>
>> Lee.
>>
>> Check the RTTY Polarity menu in your TS-2000. It probably needs to be
>> set to REVERSE. IIRC, the KAM takes care of that but your serial port
>> interface would not.
Lets see if we can drill down a little bit.
If I am reading this correctly, you are
1) transmitting FSK through MMTTY, using EXTFSK,
2) receiving through a second receiver with a KAM.
3) and the KAM tuning meter shows that you have centered the two tones
correctly.
And, when you transmit, your transmitter keys properly, and you can hear
diddles (instead of a single tone) coming from the receiver. I also assume
that the receiver and KAM can copy signals off the air?
Correct so far?
If so, your transistor circuits are working. And EXTFSK may be working (read
on).
You said that you have tried reversing polarity, is that at the receiver (KAM
end) or at the MMTTY end?
If you are trying to reverse at the KAM end, do not do it by using the FSKinv
command on the KAM. That one controls the KAM transmit direction. Instead,
turn the KAM's INVerse state on and off. (FSKinv and INVerse are different
commands, one to control the transmit and one to control the decoding)
If that makes it work, and you can copy off the air signals on the KAM without
inverting, you will need to invert MMTTY's output (see if MMTTY has an EXTFSK
invert setting, or if the transmitter has an FSK invert setting).
If you hear modulation through MMTTY's EXTFSK, and you still cannot copy by
reversing the KAM, there is one more thing that is possible: you are throwing
too many errors when using EXTFSK. EXTFSK is really a hack, where the computer
attempts to send the bits out every 22 millisecond. If there is any timing
latency in the OS, the output will not be close enough to the 22 millisecond
bit periods that the KAM expects at the receiving end. Unfortunately, you need
an oscilloscope to tell you exactly what is happening.
With most computers, the latency is around one tenth of a bit time (people will
have more problems copying you when you are weak, but they will copy you fine
when you are loud, so most people don't even know they have a problem, they
just think the receiving end has a crummy demodulator). But if you have an
old, slow machine, it could be bad enough that few characters get through.
If that is your case, some of your choices are: change software, use the K4DSP
FSKit to convert AFSK to FSK, or just change to using AFSK transmit.
BTW, you did not tell us what the KAM is printing while all of this is going
on... is it printing nothing, is it printing complete gibberish, or is it
printing a bunch of weird but repeating characters during diddles, or is it
printing correct characters now and then? Telling us that can help zeroing in
on the problem.
73
Chen, W7AY
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