I sometimes use my little dell laptop on another rig and it picks up outside
noises and even picked up the sound from my other rig and decoded it. I been
looking for the built in Mic but can't find it. No big thing but it bugs me
ED K8OT
In a message dated 2/5/2009 12:58:33 A.M. Eastern Standard Time,
k0rc@citlink.net writes:
There's other things to consider beyond the soundcard. The soundcard is
usually on the bottom of my suspect list.
In MMTTY you can select from three different demodulators by clicking the
TYPE button. Above and slightly to the left of this button will be the
acronyms FIR, IIR, and PLL as you click through them. Depending upon band
conditions at the moment, one of the three can provide better copy.
Something beyond operator control is band and path conditions. It's possible
to have a S-9 signal and not be able to decode because of bit distortion
(delay). This is especially prevalent on signals going over a polar path.
Another issue can be AC hum (ground loop). A few months back I experienced
this for the first time in my shack. I saw the ripple on the scope. It just
didn't "look right" and MMTTY wasn't decoding for beans. I figured out the
problem but I don't recall what I did at the moment.
The difference between copy and no copy is rig dependant too. I was not a
believer until I bought an Icom 756 Pro III and turned on the RTTY twin peak
filter. It brought signals out of the noise the I would never been able to
copy on my TS-950SDX... even with all of it's filters and DSP.
Another source of "self inflicted QRM" can be your own monitoring system. If
you are picking your RX audio from the external speaker, it (the
loudspeaker) will pickup room noises (another RTTY signal from a different
radio perhaps?) and feed that into your soundcard input. Now you have two
competing signals going into the MMTTY decoder.
Just a few thoughts.
73 de Bob - KØRC in MN
----- Original Message -----
From: "Iain MacDonnell - N6ML" <ar@dseven.org>
To: "Robert Chudek - K0RC" <k0rc@citlink.net>
Cc: <RTTY@contesting.com>
Sent: Wednesday, February 04, 2009 10:36 PM
Subject: Re: [RTTY] Affordable PCI sound card recommendations?
>
> Hi Bob,
>
> The problem was that weaker signals were not decoding (cleanly). It's
> difficult to quantify, but judging by ear, the signals should have been
> strong enough to fully copy. Changing from the on-board - most likely
> AC97-based (I'm not at the site now) - interface to a couple of
> different USB devices (an EMU-0202 and a Griffin iMic2) cleared the
> problem right up - those weaker signals started decoding just fine.
>
> I think I'm going to go for something in the sound blaster line. I'd
> like to have something that does most of the work in hardware, rather
> than a software codec - it just seems like that might be more reliable.
>
> Thanks for the input... and for Qs in a bunch of recent contests :)
>
> ~Iain / N6ML
>
>
>
> Robert Chudek - K0RC wrote:
>> "We've tried the on-board audio with MMTTY, and had major problems
>> decoding."
>>
>> What were the major problems you experienced decoding?
>>
>> To answer you question, virtually any soundcard will provide good
>> results. The SB Live! series work well.
>>
>> 73 de Bob - KØRC in MN
>>
>>
>> ----- Original Message ----- From: "Iain MacDonnell - N6ML"
>> <ar@dseven.org>
>> To: <RTTY@contesting.com>
>> Sent: Wednesday, February 04, 2009 9:38 PM
>> Subject: [RTTY] Affordable PCI sound card recommendations?
>>
>>
>>>
>>> I need to outfit a number of WinXP PCs at a contest station for
>>> RTTY. We've tried the on-board audio with MMTTY, and had major
>>> problems decoding. I got around this for the last contest (RU)
>>> by using external USB audio interfaces, but want to install
>>> something internal in each PC to make it permanent. I've seen
>>> a number of Sound Blaster Live! options on eBay in the order
>>> of $10-15 shipped, but thought I'd ask here if there are any
>>> particular models that work well, or are known to not work well
>>> for RTTY decoding (and maybe AFSK transmit too).
>>>
>>> TIA for any recommendations...
>>>
>>> ~Iain / N6ML
>>>
>>>
>>> _______________________________________________
>>> RTTY mailing list
>>> RTTY@contesting.com
>>> http://lists.contesting.com/mailman/listinfo/rtty
>>>
>>
>
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