[1000mp] ARRL REVIEW ROOFING FILTER

[Ron]

I totally agree if the stock filter is as wide as it sounds it is then 
there is a lot of  room for improvement but distortion at 2 KHz in my 
opinion isn't really the problem because a distortion that is down -69 
or even -79  is not problem.   What I see the issue being is  that the 
stock filter at 20 KHz is down 130 db in comparison to the  new filter 
which is down the same 130 dB  at only 5 KHz.   Yes rejecting 15 KHz 
worth of signals will  for sure improve the received signal audio.   
Intermodulation for two signals that are 20 KHz away on the old  filter 
should be the same as the new filter at 5 KHz away.    Sounds like I 
need one of the filter for my  radio.  I wonder where the Yaesu 
engineers had their heads at when they made that filter so wide.  
Obviously  it was a cost issue. 

Ron  WA0KDS  









Earl W Cunningham wrote:

>Ron, WA0KDS wrote:
>
>"There  is no  way that anyone can tell the difference between -69 and
>-79 .  The ear is just not that good. Sorry.  A lot of hype out there to
>sell radios and filters."
>==========
>Ron, on a quiet band (with no strong signals nearby in frequency) you'll
>probably won't hear any difference.
>
>The INRAD roofing filter vastly improves the IMDDR3 and BDR of the
>receiver.  For example, when I use my FT-1000MP (without the INRAD
>roofing filter) in a crowded band with many strong signals (especially
>during contests), I have to crank in 6 dB of front panel attenuation to
>get rid of the chirps and birdies caused by the IMDDR3 products produced
>by two (or more) strong signals on the band (within the bandpass of the
>stock roofing filter, which is 20 kHz, I believe).  But that 6 dB of
>attenuation makes it more difficult to hear the weaker signals.
>
>If I had the narrower INRAD roofing filter, that 10 dB of improvement in
>IMDDR3 (at 2 kHz spacing) would negate the need to use any front panel
>attenuation because I wouldn't hear the chirps and birdies I normally
>would.
>
>I've never had a problem with BDR, but the ARRL test results for that
>parameter are also quite impressive.
>
>No, I'm not going to buy the INRAD filter because I have a different
>radio that I like better for contesting and DXing, but for you contesters
>that prefer using the MP series of radios, it looks like a "must have".
>
>73, de Earl, K6SE
>
>
>  
>