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250 Hz filter might be expected to improve S/N ratio by 3 dB compared to 500
Hz filter.
Two carriers are attenuated due to increased in-band losses of narrower
filter.
Certain amount of energy is lost on FSK signal sidebands.
However, subjective gain on the ears sounds convincing. Bit error rates
might show otherwise.
Once upon a time, there were nice FSK spectrograms at HAL site.
I use 500 Hz @ 9 MHz most of the time, 250 Hz @ 455 kHz to fight close QRM
only.
73 de Mario, S56A, N1YU
----- Original Message -----
From: Ekki
To: _Rtty
Sent: Tuesday, August 28, 2001 9:34 PM
Subject: RE: [RTTY] Bandwidth of a RTTY signal (was:SO2R RTTY Radio)
> At 10:17 PM 8/28/01 +0200, Ekki wrote:
> >> If possible, use a 250 Hz filter for RTTY. 500 Hz is ok for Pactor
but
> >> unnecessarily wide for RTTY.
> >
> >I beg to differ :-)
>
> Well I beg to differ )!
>
> I have used 250 Hz filters in my final IF for RTTY operation since 1985
or
> so in contests. I have used them with Icom 751, Icom 761, Icom
> 765, Kenwood
> 850, Yaesu FT-1000, Icom 706, Kenwood 940, Kenwood 930, Yaesu 990. All
> stock manuf. filters.
[more deleted]
I didn't say that 250Hz filters wont work at all :-) It's just that theory
suggests that 250Hz could be too narrow. I know that real world filters
never have 250 as exact cutoff edges (as mentioned in my post).
Stock CW filters, all right, so why does Icom sell a "RTTY" filter @ 350Hz
?
Anyway, everybody uses what's best for him or her, as long as everybody
has
fun and good contest results (as Bill, W7TI to whose post i responded,
obviously has :-)
73,
Ekki, DF4OR
_______________________________________________
RTTY mailing list
RTTY@contesting.com
http://lists.contesting.com/mailman/listinfo/rtty
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<DIV><FONT face=3DArial size=3D2>250 Hz filter might be expected to =
improve S/N=20
ratio by 3 dB compared to 500 Hz filter. </FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Two carriers are attenuated due to =
increased=20
in-band losses of narrower filter.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2><FONT face=3DArial =
size=3D2>Certain amount of=20
energy is lost on FSK signal sidebands.</FONT> </FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>However, subjective gain on the ears =
sounds=20
convincing. Bit error rates might show =
otherwise.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2>Once upon a time, there were nice FSK =
spectrograms=20
at HAL site.</FONT> </DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>I use 500 Hz @ 9 MHz most of the time, =
250 Hz @ 455=20
kHz to fight close QRM only.</FONT></DIV>
<DIV><FONT face=3DArial size=3D2></FONT> </DIV>
<DIV><FONT face=3DArial size=3D2>73 de Mario, S56A, N1YU</FONT></DIV>
<BLOCKQUOTE=20
style=3D"PADDING-RIGHT: 0px; PADDING-LEFT: 5px; MARGIN-LEFT: 5px; =
BORDER-LEFT: #000000 2px solid; MARGIN-RIGHT: 0px">
<DIV style=3D"FONT: 10pt arial">----- Original Message ----- </DIV>
<DIV=20
style=3D"BACKGROUND: #e4e4e4; FONT: 10pt arial; font-color: =
black"><B>From:</B>=20
<A title=3Dekki@plicht.de href=3D"mailto:ekki@plicht.de";>Ekki</A> =
</DIV>
<DIV style=3D"FONT: 10pt arial"><B>To:</B> <A =
title=3Drtty@contesting.com=20
href=3D"mailto:rtty@contesting.com";>_Rtty</A> </DIV>
<DIV style=3D"FONT: 10pt arial"><B>Sent:</B> Tuesday, August 28, 2001 =
9:34=20
PM</DIV>
<DIV style=3D"FONT: 10pt arial"><B>Subject:</B> RE: [RTTY] Bandwidth =
of a RTTY=20
signal (was:SO2R RTTY Radio)</DIV>
<DIV><BR></DIV>> At 10:17 PM 8/28/01 +0200, Ekki wrote:<BR>> =
>> If=20
possible, use a 250 Hz filter for RTTY. 500 Hz is ok for Pactor=20
but<BR>> >> unnecessarily wide for RTTY.<BR>> ><BR>> =
>I=20
beg to differ :-)<BR>><BR>> Well I beg to differ =
)!<BR>><BR>> I=20
have used 250 Hz filters in my final IF for RTTY operation since 1985=20
or<BR>> so in contests. I have used them with Icom 751, Icom 761,=20
Icom<BR>> 765, Kenwood<BR>> 850, Yaesu FT-1000, Icom 706, =
Kenwood 940,=20
Kenwood 930, Yaesu 990. All<BR>> stock manuf. =
filters.<BR>[more=20
deleted]<BR><BR>I didn't say that 250Hz filters wont work at all :-) =
It's just=20
that theory<BR>suggests that 250Hz could be too narrow. I know that =
real world=20
filters<BR>never have 250 as exact cutoff edges (as mentioned in my=20
post).<BR><BR>Stock CW filters, all right, so why does Icom sell a =
"RTTY"=20
filter @ 350Hz ?<BR><BR>Anyway, everybody uses what's best for him or =
her, as=20
long as everybody has<BR>fun and good contest results (as Bill, W7TI =
to whose=20
post i responded,<BR>obviously has :-)<BR><BR>73,<BR>Ekki,=20
DF4OR<BR><BR>_______________________________________________<BR>RTTY =
mailing=20
list<BR><A =
href=3D"mailto:RTTY@contesting.com";>RTTY@contesting.com</A><BR><A=20
=
href=3D"http://lists.contesting.com/mailman/listinfo/rtty";>http://lists.c=
ontesting.com/mailman/listinfo/rtty</A></BLOCKQUOTE></BODY></HTML>
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