[TenTec] Orion Roofing Filter Cut In

[Bob Henderson]

Well I'm really no expert and I think Ten Tec's basis for the decision to
deploy roofing filters when DSP b/w is at 75% of roofing b/w would be better
explained by them.

Having said that, I offer the following observation:

Roofing filters are not intended to contribute anything to the definition of
overall system b/w.  They are intended to avoid overload of those RX stages
prior to the main b/w determining filters.  If roofing filters are switched
in at DSP b/w = Roofing b/w then they will inevitably contribute to
determining overall system b/w.  A margin is necessary to avoid this.  The
question would appear to be: Does DSP b/w = 75% Roofing b/w provide an
appropriate margin or an unecessarily wide one?

Incidentally, the 1.8kHz roofing filter can be used on SSB.  It can be
manually selected from the menu, not just manually disabled.

Bob, 5B4AGN, P3F


----- Original Message ----- 
From: <K4IA at aol.com>
To: <tentec at contesting.com>
Cc: <ditsnbits at tentec.com>
Sent: Thursday, August 05, 2004 1:42 PM
Subject: [TenTec] Orion Roofing Filter Cut In


> I am confused by the scheme used to automatically cut in the Orion roofing
> filters.
>
> Why does the filter not cut in until the DSP bandwidth is substantially
less
> than the filter?
>
> For example, the 2.4 filter doesn't switch in until the DSP is at 1.990.
>
> The 1.8 doesn't engage until the DSP is at 1.400  This is way too narrow
for
> SSB - thus there is no effective roofing filter for narrow SSB and one
could
> argue this roofing filter is useless for SSB.  Yes, I know you can set the
> passband for +150 and still be able to decipher SSB at that narrow a DSP
setting,
> but speech is very difficult to understand.
>
> The 1.0 comes in at .740  Is this one of the reasons some have switched
out
> the 1.0 in favor of the INRAD 600 in this position?
>
> The 500 is at 350.  I don't have the 250 so I can't comment on that one.
>
> Wouldn't it make more sense to have the roofing filter match the DSP?
>
> Would it make sense to have the roofing filter kick in "early" as the
INRAD
> 600 does when placed in the 1.0 position?
>
> Radio k4ia
> "Buck"
> Fredericksburg, Virginia USA
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