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@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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