I noticed the same thing as I started getting to know my new Orion. I
think that part of the confusion is that the roofing filters are not the
signal bandwidth filters that we are used to seeing advertised in other
rigs. The roofing filter sets the overall operational bandwidth that the
receiver front end sees. The signal bandwidth is set using the DSP
bandwidth control.
Having said that, I think that TenTec confused the situation by using
1.8 and 2.4 kHz values for their "SSB" roofing filters. Plain and simple, I
think that these filters are a mistake for those of us who enjoy mostly
using SSB! Why? They are too narrow.
I think that it is reasonable and prudent to have a roofing filter that
is somewhat wider than the desired signal bandwidth. How much wider? 20%?
50%? 100%? I don't know, but I suppose that there are performance and cost
trades that establish the optimal range.
I don't know about the rest of you, but I have great difficulty copying
SSB with a bandwidth less than 2.0 kHz. I have had rigs with 1.8 and 2.0
kHz signal bandwidth filters and I just didn't use them. They did me no
good. I normally set my Orion signal bandwidth between 2.1 and 2.8 kHz
depending on the band conditions. On automatic filter selection, I just
don't use the 2.4 kHz roofing filter. It is too narrow. I could, of
course, select it and lock it.
So, back to the TenTec mistake, IMO. I think that they should have
selected a "SSB" roofing filter of about 3.5 kHz and forgotten about the 1.8
and 2.4 kHz filters. A 3.5 kHz roofing filter probably would have allowed
DSP bandwidth settings of 2.8 kHz or less. I think that would have been
"ideal" for us SSB operators. The 6.0 kHz filter, IMO, is a little too wide
for DX who are using a 5.0 kHz split. We need something narrower for the
heavy QRM.
I do have a question for any of you who have both the 1.8 and 2.4 kHz
filters. Have you tried setting the DSP bandwidth at 1.75 kHz or so, and
then tried both the 1.8 and 2.4 filters on various SSB signals? Did you
hear any difference?
Don't get me wrong, I really like my Orion. I just think that TenTec
selected the "wrong" SSB filters. I suppose that they were more focused on
CW operation.
Just one man's opinion.
Comments??
73s
Bernard, WA4OEJ
----- Original Message -----
From: <K4IA@aol.com>
To: <tentec@contesting.com>
Cc: <ditsnbits@tentec.com>
Sent: Thursday, August 05, 2004 8:42 AM
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
> _______________________________________________
> TenTec mailing list
> TenTec@contesting.com
> http://lists.contesting.com/mailman/listinfo/tentec
>
_______________________________________________
TenTec mailing list
TenTec@contesting.com
http://lists.contesting.com/mailman/listinfo/tentec
|