I use 250 Hz crystal filters in my IC751A in bot the 9MHz and 455 KHz IF. I
use 250 Hz DSP filters in my IC-7600 ALL the time.
Works perfectly.
I use MMTTY, 2Tone and a HAL-ST8000 for decoders.
73
Jim W7RY
-----Original Message-----
From: Joe Subich, W4TV
Sent: Thursday, January 10, 2013 7:22 AM
To: Al Kozakiewicz ; RTTY
Subject: Re: [RTTY] RTTY spectrum analysis article
Then how do you keep strong signals in the passband of the (now
wider) rig filter away from the AGC in the rig?
400 Hz is nearly the minimum bandwidth necessary for proper decoding
(minimum intersymbol interference). Narrower filters work by cutting
adjacent signals more than the desired signal but they impose a much
higher group delay than a filter that is "flat" across the necessary
350 to 370 Hz bandwidth.
73,
... Joe, W4TV
On 1/10/2013 9:44 AM, Al Kozakiewicz wrote:
Then how do you keep strong signals in the passband of the (now wider) rig
filter away from the AGC in the rig? Attenuating a strong signal now in
the passband also attenuates the weak adjacent ones I'm trying to work,
no?
Ignorance is a powerful sedative, so perhaps I don't know what I'm
missing, but the 250hz RTTY filter in my Icom radios turned me from a 150
QSO/contest frustrated S&Per into a 1200 QSO/contest participant that
enjoys the time spent in the chair!
Al
AB2ZY
________________________________________
From: Jeff Blaine [keepwalking188@yahoo.com]
Sent: Thursday, January 10, 2013 9:34 AM
To: Al Kozakiewicz; RTTY Mailing List
Subject: Re: [RTTY] RTTY spectrum analysis article
The best place for RTTY rx filtering is in the demod, not the rig. narrow
crystal filter and it's group delay gives more problems than it solves.
The solution is to run a filter wide enough to let you quickly tune
(400-500
hz?), but not so razor sharp that the rig rather than the demod is doing
the
selectivity filtering.
73/jeff/ac0c
www.ac0c.com
alpha-charlie-zero-charlie
-----Original Message-----
From: Al Kozakiewicz
Sent: Thursday, January 10, 2013 8:30 AM
To: RTTY Mailing List
Subject: Re: [RTTY] RTTY spectrum analysis article
No, this doesn't necessarily mean you should give
up "true" FSK keying. There are things you can do about it, and some
people are people taking responsibility and doing these things--please
read
the
article!
That was depressing. Transmit filters are only enabled on the Icom radios
I
have on SSB, so there is no apparent option for improvement that I can see
for without switching to AFSK which, in turn, makes the radios just about
useless for contesting as there is no practical way to use the RTTY Rx
filters without also transmitting FSK.
Unless I missed it in the article, I see no way to improve things short of
buying a new radio with a design that does not currently exist!
Al
AB2ZY
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