I have a hard time visualizing the need for a narrow filter, for such narrow
modes. You can sit, in PSK for instance, slap up against another PSK signal
and still copy much weaker signals. Thats the whole purpose of the narrow
band digital modes to start with. I use WinWarbler (now) to do my digital
transmission in both PSK and RTTY, and when I want to do something like
Olivia or MFSK etc. I go to MixW. I particularly like WinWarbler because it
has the wide band copy ability in PSK. I.E it will automatically copy (and
show all the channels) in a 2 or 3 KC bandwidth - at the same time. Using a
narrow filter in there would completely negate that fantistic capability.
I have never had to use my narrow filters in order to copy a digital
signal, and yes I have played with them to see what difference it made.
Todays rigs, with their dsp filtering just seem to bypass any need at all
for additional filters for digital operation, though I do see the need for
CW filters, and have 250 and 270 cy fliters in my two rigs because I use my
ears, and not the computer to detect and read that mode.
Danny Douglas N7DC
ex WN5QMX ET2US WA5UKR ET3USA
SV0WPP VS6DD N7DC/YV5 G5CTB all
DX 2-6 years each
.
QSL LOTW-buro- direct
As courtesy I upload to eQSL but if you
use that - also pls upload to LOTW
or hard card.
moderator [EMAIL PROTECTED]
moderator http://groups.yahoo.com/group/DXandTalk and RTTY,
Danny Douglas N7DC
ex WN5QMX ET2US WA5UKR ET3USA
SV0WPP VS6DD N7DC/YV5 G5CTB all
DX 2-6 years each
.
QSL LOTW-buro- direct
As courtesy I upload to eQSL but if you
use that - also pls upload to LOTW
or hard card.
moderator [EMAIL PROTECTED]
moderator http://groups.yahoo.com/group/DXandTalkK vfor i
Danny Douglas N7DC
ex WN5QMX ET2US WA5UKR ET3USA
SV0WPP VS6DD N7DC/YV5 G5CTB all
DX 2-6 years each
.
QSL LOTW-buro- direct
As courtesy I upload to eQSL but if you
use that - also pls upload to LOTW
or hard card.
moderator [EMAIL PROTECTED]
moderator http://groups.yahoo.com/group/DXandTalk
----- Original Message -----
From: "kv9u" <[EMAIL PROTECTED]>
To: <digitalradio@yahoogroups.com>
Sent: Wednesday, March 07, 2007 2:24 PM
Subject: Re: [digitalradio] narrow filters/PSK
> Hi Dave,
>
> Yes, the narrower filters will help a great deal. I have an ICOM rig
> that needs to be centered on 1500 Hz when operating in SSB modes so I
> try and move them to that point if I can. Then I have DSP filters that
> enable me to close the "window" as tight as I need to. I also have Twin
> PBT which enables me to dial each side of the interference. But the
> actual bandpass filters are much more effective with the really strong
> signals.
>
> If I could only have one additional filter than the stock SSB filter, I
> would go for the 500 Hz filter since it is very useful for CW use as
> well as narrow to medium digital modes. I have a 270 Hz crystal filter
> in my Kenwood TS-440SAT that I find rather narrow although some might
> prefer that for CW.
>
> If you go narrower than 500 Hz, you can not use a number of digital
> modes that are around or slightly under 500 Hz, but may not fit well
> into at 250 Hz bandpass.
>
> 73,
>
> Rick, KV9U
>
> Dave wrote:
> > Has anyone tried using either a 250 Hz or 500 Hz filter for PSK31
> > reception? My Icom IC-746 (non-Pro) has no filters installed, and is
> > wide as a barn door on USB for PSK31. I wondered if either of these
> > filters would help, or would they be too narrow?
> >
> > The pass-band shift does a fair job of eliminating QRM from one side
> > or the other of the selected frequency, but when there are two very
> > strong signals within 2 Khz on each side at the same time, they just
> > aren't effective on both.
> >
> > Any input appreciated!
> >
> > Thanks in advance es 73
> > Dave
> > KB3MOW
> >
> >
>
>
>
>
>
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