The frequencies used for intermediate frequency are not the same in the
FT450 as the FT1000 series.  I don't know all the details; gave up looking
for the FT450 manual.  In the 450, you have a first IF of almost 67 MHz.
The third IF, where the DSP takes place and the variable bandwidth is set,
is probably around 24 or 30 KHz.  If it is like the 950, the second IF is
450 KHz, which is the only place where a mechanical filter would work.  In
the FT1000, people probably considered the filter at 8.2 MHz to be the
roofing filter; I'm not sure.

The DSP filter in your 450 has the steep slopes and sharp cut-off
characteristic of mechanical filters.  You are hung up on roofing filters.
They help reject interference 5 or more KHz away, but are not designed to
provide much selectivity against signals that are 2 to 3 KHz away, such as
adjacent SSB channels.  The exception to this statement is the TS590 and the
K3, which use multiple filters at different frequencies to achieve sharp
selectivity.  They add cost to the rig if you need multiple bandwidths,
whereas DSP filtering allows you to select from a number of bandwidths at
little additional cost.  I hope this makes a little sense.
73,
Lloyd Rasmussen, W3IUU, Kensington, Maryland
Home:  http://lras.home.sprynet.com
Work:  http://www.loc.gov/nls
 
> -----Original Message-----
> From: For blind ham radio operators [mailto:[log in to unmask]]
> On Behalf Of Michael Ryan
> Sent: Monday, July 18, 2011 8:09 AM
> To: [log in to unmask]
> Subject: 10 Pol Colins Mechanical Filter
> 
> Hi All:=20
> 
> Just reading up on the Yaesu FT-1000 Mark V and it mentioned that this =
> transceiver came standard with a 10 Pol Colins Mechanical filter.=20
> Was this the prede sesser to todays modern roofing filter? What was the =
> narrowing capability of this filter?=20
> I also see that this rig had the ability to plug in 2 2KHZ SSB filters, =
> 1 in the 455KHZ IF and 8.2KHZ IF 2 250CWs 1 for the 455KHZ and 8.2
> IFs.=20=
> 
> What is the difference between these with regards to actual hearing and =
> filtering characteristics? ? When I activate the narrow filter setting =
> on my FT-450, do I hear the 8.2 IF at 1.8KHZ and 500 or is this the =
> 455KHZ IF?=20
> 
> TNX & 73:=20
> 
> Michael De VO1RYN=20