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Re: [RTTY] RTTY Tx options - advice requested

To: "'Dave Hachadorian'" <k6ll.dave@gmail.com>
Subject: Re: [RTTY] RTTY Tx options - advice requested
From: "Ed Muns" <ed@w0yk.com>
Reply-to: ed@w0yk.com
Date: Mon, 1 Dec 2014 09:45:28 -0800
List-post: <rtty@contesting.com">mailto:rtty@contesting.com>
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:
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.



-----Original Message-----
From: RTTY [mailto:rtty-bounces@contesting.com] On Behalf Of Dave
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 

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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