[RTTY] RTTY Tx options - advice requested

[Joe Subich, W4TV]

> You are using a K3. I tried to overdrive my K3 by turning all the
> "knobs to the right" on the K3 and the PC sound card. I then listened
> on my other K3 and I could not hear any audio harmonics at all on the
>  transmitted signal. This was with the 2Tone AFSK filter off.

You probably had CONFIG:AFSK TX = FIL On which inserts a narrow filter
around the selected tones *in the K3 DSP Modulator*.  That does a very
good job of narrowing non-coherent AFSK and getting rid of any hum or
harmonics introduced in the audio sages.

Unfortunately, that filter is unique to the K3 - none of the YaeComWood
transceivers offer such a filter - and maladjusted AFSK is worse than
the wider than optimal FSK they produce.

73,

   ... Joe, W4TV


On 2014-12-01 1:17 PM, David G3YYD wrote:
> Dave
>
> You are using a K3. I tried to overdrive my K3 by turning all the "knobs to
> the right" on the K3 and the PC sound card. I then listened on my other K3
> and I could not hear any audio harmonics at all on the transmitted signal.
> This was with the 2Tone AFSK filter off. I always use 1275/1445Hz tone pair.
>
> Conclusion just use the tone pair you want to with the K3. But better not to
> have all the knobs to the right.
>
> By the way I also always use VOX with the delay turned down to the minimum.
> This saves having to fiddle around with a PTT line.
>
> 73 David G3YYD
>
> -----Original Message-----
> From: RTTY [mailto:rtty-bounces at contesting.com] On Behalf Of Dave
> Hachadorian
> Sent: 01 December 2014 15:54
> 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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