[Yaesu] Filter Improvements for FT-1000D

[Joe Subich, K4IK]

Ed, 

> > > > 2800 Hz Inrad instead of the standard 2400 Hz Yaesu
> > > > 2100 Hz Inrad as optional SSB
> > > 
> > > I take it you prefer leaning a bit more towards "high
> > > fidelity" audio, vs. maximizing selectivity.
> > 
> > Yes, Hans likes the higher fidelity audio on SSB <G>.  Based 
> > on their part number, each of the Yaesu filters (8.215 MHz and 
> > 455 KHz) are actually 2600 Hz wide at the -6 dB points.  When 
> > cascaded, they yield 2400 Hz overall at the -6 dB points. 
> > 
> That all makes sense, and I don't see much wrong with it if they 
> are good filters.  But specifying BW at the 6dB points is kind of 
> nonstandard, and I can see why some might want a little more BW. 

It is standard to specify bandwidth at the - 6 dB points.  When  
any two filers of similar bandwidth are cascaded, the effective 
bandwidth is somewhat less than a single filter alone.  

I can also see why some might want a wider bandwidth but I've 
never felt the need.  The INRAD "2800 Hz" filter pair have 
individual -6 dB bandwidths of 2888 and 2912 Hz respectively. 
Since the 3rd IF filter is slightly wider than the 2nd IF, 
the cascaded bandwidth will be very close to 2800 Hz at -6 dB 
and around 3500 - 3700 Hz at -60 dB vs. around 2400 Hz at 
-6 dB and 3400 - 3600 Hz at -60 dB for the stock filters.

> I rarely use CW, and would never use CW in a contest; so the 
> performance of the standard 1000D filter seems fine to me.  
> The only reason why I might want to change it would be if 
> I wanted a substantially wider BW, per Hans' idea.  

If you have an FT-1000 (non-D) and have no need for 250 Hz, then 
putting a pair of 1000 Hz filters in the 250 Hz slots might be 
intriguing.  

> > BTW, the INRAD web site indicates the FT-1000D roofing filter 
> > is available (delivery at Dayton).  Based on the results in my 
> > Mark V, I would make a roofing filter the first filter addition 
> > to an FT-1000/FT-1000D.  
> > 
> Now this sounds interesting.  But would this be a hack-type 
> modification, or does the 1000D have an available "slot" for 
> a roofing filter?  

It's not particularly a "hack."  The roofing filter and post 
amplifier is designed to mount in an empty space on the chassis. 
Two wires are run to an adjacent circuit board for 5 volts and 
ground.  One coax is unplugged from the circuit board and moved 
to the roofing filter and a coax jumper is connected between 
the roofing filter board and IF board. 

> > 2) INRAD 400 Hz CW filter for the sub receiver 
> 
> If one replaced the Main Rx 500 Hz filter with one of these, 
> could the standard filter from the Main be trickled down to 
> this spot in the Sub?  

No, the center frequencies are different (455.0 KHz for the 
main vs. 455.7 KHz for the sub-receiver). 

> Also, if one wanted to minimize "unauthorized" mod's, couldn't 
> one just add another standard 500 Hz filter to the (presumably 
> open) "slot" in the Sub?  

Not a "standard" main receiver filter - the center frequencies 
and physical shape are different.  However, INRAD has a 500 Hz 
filter that is a drop in replacement for the Yaesu XF-455MC 600 
Hz filter. 

> > 3) replace the Murata ceramic filter in the sub-receiver 
> >    with an INRAD 702 
> 
> That would be nice.  Would another of the original Yaesu 
> XTAL filters (same as the Main) be another option? 

Yes, if one can find the Yaesu 2.6 KHz (XF-455K-262-01) filters. 
Another option might be a 10 pole Collins 2.4 KHz filter from 
INRAD (717). 

> > 4) add the optional 250 Hz 3rd IF filter if necessary.
> 
> Would the benefit of this simply be that selecting a 250 BW 
> would also give that BW in the Sub, instead of the Sub 
> just staying at 400/500 Hz?    

No, the 250 Hz bandwidth is available only in the main receiver 
unless one chooses to 'wire in' a 250 Hz filter as the only 
CW filter in the sub-receiver (the sub-receiver supports only 
one CW filter).   

73, 

   ... Joe, K4IK