[Yaesu] FW: roofing filters

[Keith Dutson]

AFAIK, the original Icom 7800 had 15KHz and 6KHz selectable roofing filters.
The 9000 has 15, 6 and 3.  According to the 2000 manual I saw, it also has
15, 6 and 3.  I understand there is now a free upgrade to add 3 to the 7800.
The Orion was the first radio I saw with roofing filters and they are
selectable down to 1KHz, with 500Hz as an option.

To me, roofing filters are really useful in reducing the harmful effects of
AGC caused by reception of unwanted signals (2-10KHz away).  My brain is
pretty good at separating one signal from the other, but when AGC drops both
signals, noise seems to win out over intelligibility.  In the lab, I believe
the net result shows up as blocking dynamic range at 2KHz spacing.

The newer receivers such as 756 Pro III, Orion, 7800, 9000 and now 2000
(according to manual) have excellent front ends.  DSP is often claimed to do
amazing things to reduce or eliminate interference.  However, compared to
the original 1000 series, I do not see a quantum leap in performance.  There
are definite improvements but the operator has to do a lot of studying and
experimenting to get improved performance out of the rig.

Personally, I have two 9000D's, an Orion and an Icom 775DSP.  Learning how
to effectively use the Orion took at least two months of concentrated study
and use.  Learning how to use the 9000 is a whole new ball game.  After four
months of reading the manual and fiddling with knobs and buttons, I have
mastered use of about 50 percent of the available features.  I hope to have
experimented with everything else within a year.

73, Keith NM5G

-----Original Message-----
From: yaesu-bounces at contesting.com [mailto:yaesu-bounces at contesting.com] On
Behalf Of Cecil Acuff
Sent: Friday, July 21, 2006 8:16 AM
To: farson at shaw.ca; Yaesu Contesting Reflector
Subject: Re: [Yaesu] FW: roofing filters

It is my understanding that the Pro III implemented a fixed 15Khz roofing
filter like that used in the 7800 but the earlier Pro II (which I had) did
not.  All the reading I have done on the subject indicates the 15Khz to be
too wide to provide the full benefit so now we are seeing rigs with two and
three selectable and narrower roofing filter bandwidths.  I believe the new
FT-2000 is coming that way from the start.

The Sherwood Engineering page has good explanations of the whole roofing
filter issue as does the Inrad page.

Also a correction to my earlier post....about close spaced test results was
suppose to say Dynamic Range not IMD....My confusion on that one...

Cecil...
----- Original Message -----
From: "Adam Farson" <farson at shaw.ca>
To: "Yaesu Contesting Reflector" <yaesu at contesting.com>
Sent: Friday, July 21, 2006 1:14 AM
Subject: [Yaesu] FW: roofing filters


> Hi Cecil,
>
> Er...the IC-756Pro series does have 15 kHz roofing filters at the first
> (64.455 MHz) and second (455 kHz) IF's.
>
> Cheers for now, 73,
> Adam VA7OJ/AB4OJ
>
>
>
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