You've outlined many of the problems with various RTTY TX options.
For me, 2Tone is unacceptable for TX and the primary RX, mainly due to the
2-3 character delay at the start of each. This is a larger contesting issue
than the few times it decodes better than MMTTY or other decoders.
FSK is my personal choice for two reasons. First, I don't trust myself to
keep the levels in the right range throughout the distractions of
contesting. Second, low tones are a huge benefit over the course of a
contest and I won't risk possible harmonics from AFSK. The K3 doesn't
magically solve the harmonic problem. A local here used low tones with AFSK
and his K3 which wiped out a broad swath of the band with the harmonics.
Accordingly, I use MMTTY as the primary decoder and WriteLog's Rttyrite
Software Generated FSK for transmit. Minimum bit jitter requires some
combination of a powerhouse PC and elimination of all other processing in
Windows. My contesting PCs are not quad core, but a fast-enough dual core
in this limited application. I dedicate each PC to a single radio and it
only runs the logger, nothing else. Even in the few contests where I use
Packet (WPX RTTY and Ten-Meter RTTY), I run VE7CC on a separate PC that
feeds the logging PCs.
N1MM users don't have the Rttyrite FSK option. But, MMTTY FSK is tolerable
despite its bit timing issues (another lengthy explanation). I don't know
how much these MMTTY FSK issues affect copy on the receiving end. Over a
decade of use by hundreds of MMTTY FSK contesters at least establishes that
it is "pretty good", if not ideal.
I think the best FSK option available today is the TinyFSK by K0SD:
http://www.frontiernet.net/~aflowers/tinyfsk/
Unfortunately, it only works with N1MM, otherwise I'd build a bunch of them
for use with WriteLog. It is pretty easy to build but I don't know if you
can gather the parts and get it done by Saturday.
Another option would be to use the Hal DXP38 for FSK, but I don't know if
anyone has done this with N1MM yet. If you don't want to use the DXP38 as
your primary decoder, you can just dedicate a DI window to FSK TX only and
have 2Tone or MMTTY as your primary decode DI window. Or, perhaps some
other hardware TNC you may have available.
Ed W0YK
________________________________________________________________________
-----Original Message-----
From: RTTY [mailto:rtty-bounces@contesting.com] On Behalf Of Dave
Hachadorian
Sent: 01 December, 2014 07:54
To: reflector RTTY
Subject: [RTTY] RTTY Tx options - advice requested
We've got the 10 Meter RTTY Contest coming up this weekend, and
I'm trying to figure out the best way to do the RTTY Tx function.
I think the combination of switching to N1MM LoggerPlus, and
switching to 2Tone as primary decoder have raised some issues.
Here are some available options as I see them:
I could do AFSK, but I've grown accustomed to hearing the
915/1085 Hz tone pair, and apparently that's dangerous because
the harmonics fall into the 2.7 KHz passband of the SSB filter.
Can I get away with that tone pair? I'm using a K3 radio,
I love 2Tone for receiving, but apparently its FSK Tx is subject
to timing jitter if the computer is not a quad-core powerhouse.
My computer is pretty good, but not THAT good.
I have the parts lying around for G3YYD's deluxe pseudo-FSK
circuit, with the comparator IC. I could jump back onto that
project and probably get it done in time for the weekend.
The FSKit sounds like a good option, but apparently the circuit
boards and programmed controllers are no longer available. If
someone has one to sell, I'd like to hear from you.
I could use MMTTY for Tx. Apparently its FSK is not subject to
timing jitter? I could then use 2Tone in a separate Rx-only
window, but then I wouldn't see my transmitted text in that
window, which is unnerving. I could move my eyeballs between the
two windows for Tx/Rx, but that is suboptimal. Overall, this
sounds like the most certain approach though. Is MMTTY FSK
timing solid, even on a moderate-speed computer? I'm using a
real PCI serial port card.
Is there an inexpensive hardware modem that I could use for RTTY
Tx-only?
I would appreciate comments on the above options. If anyone has
a better idea, please let us know.
Many thanks.
Dave Hachadorian, K6LL
Yuma, AZ
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