[1000mp] cw audio loud

[Earl W Cunningham]

N3DRK wrote:

"Here are some figures provided by George,w2vjn, the owner of Inrad
Filters.

Selectivity: Quartz vs. Silicone

Filter          FT1000MP          Orion          756Pro3          IC7800
2400Hz          3000              2784           3360             3864
500             775               950            985              1850
250             415               750            734              1550

The FT1000MP is the only transceiver which has Inrad Crystal Filters. All
the others are DSP."
==========
I question whether the test FT-1000MP has all INRAD filters in it
because, to my knowledge, George doesn't have a 500 Hz xtal filter for
the MP.  He does have a 400 Hz xtal filter for it, and it is only for the
455 kHz IF.  He does have a 500 Hz Collins mechanical filter, but
mechanical filters do not have nearly as steep slopes as xtal filters.

The MP comes stock with a "standard" 2400 Hz filter in the 8.215 MHz IF
and a 2750 Hz Collins mechanical filter in the 455 kHz IF.  It also has a
"standard" 500 Hz filter in the 8.215 MHz IF.  The "standard" filters are
not mechanical and are probably either xtal or ceramic.  At any rate,
they are wired in and not as readily replaceable as the optional filters
which have plug-in slots.  The test MP probably had George's filters
wired into the "stock" slots because Yaesu's 60 dB BW specs are
substantially wider (2400 = 4200 Hz, 500 = 1800 Hz and 250 = 700 Hz) than
the figures in the above table.

Although the above table does not specify it, I assume that the
measurements on the MP were taken with both the 8.215 and 455 IF filters
cascaded.

I have George's 125 Hz xtal filter in my MP's 455 IF and cascaded with a
Yaesu 250 Hz filter in the 8.215 IF, and it does a commendable job. 
(Sorry, George.  I didn't know about your filters until after I ordered
the Yaesu filters.)

My preferred radio now is my Icom 756Pro3, partly because the DSP
filtering goes down to a BW of 50 Hz, giving me a noticeable improvement
in S/N ratio for copying extremely weak CW signals.  I don't have any
elaborate test gear, but I just tried the 50 Hz filter on a steady
carrier and could not hear the beat 40 Hz above and below the signal,
which is a BW of 80 Hz at probably greater than 60 dB down. That's pretty
steep skirts if the 50 Hz BW is at only 6 dB down.

I'd like to see a similar table which compares narrow BWs of 150 Hz and
less.

73, de Earl, K6SE