Dave,
Yes, a 400Hz filter will work well for RTTY (and CW too).
73,
Don W3FPR
On 2/21/2017 6:27 PM, Dave Fugleberg wrote:
Don, that's a great explanation. I came to the same conclusion in a
recent RTTY contest. I built my K3 with the single stock filter based
on advice from a number of folks to 'just operate for awhile til you
get the feel for what other filters you need'. I think that's sound
advice.
Anyhow, I've been generally ok with the standard filter and relying on
DSP filtering to narrow it as needed. However, in the RTTY contest, I
often had issues working weaker stations when strong ones were very
close by. It was easy to see what was going on by watching the P3- I'd
start copying a signal inside the DSP bandwidth, and a strong one
would pop up just above or below that station. Even though I couldn't
hear the strong station, the weak one would go nearly silent as the
AGC kicked in due to the strong signal in the IF passband.
So, I think I've learned that I need a narrower filter for such
situations. I'm thinking a 400hz filter is what I want. Any reason for
a different selection in that scenario?
73 de W0ZF
On Tue, Feb 21, 2017 at 8:52 AM Don Wilhelm <donw...@embarqmail.com
<mailto:donw...@embarqmail.com>> wrote:
Mike,
Think about it - if there are multiple signals in the passband,
the AGC
will respond to the strongest, there is just no way around that fact.
If the signals can be separated by the DSP, and one is really strong,
that strong station may be activating the Hardware AGC. The only
solution for the latter is a more narrow roofing filter - put the
offending strong signal out of the passband of the roofing filter and
use shift to get your sidetone for the desired signal back in order.
That may be too much "fiddling" for a run station in a contest, but it
is a viable way to operate when trying to copy a weak station working
close to a strong station.
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