Greetings D. Kremp..

Typically, for very narrow CW work, 250 Hz IF filters are a reasonable
choice. Many prefer 500 Hz however, if you frequent very crowded band
conditions, you may have little alternative but to narrow up the IF as
much as possible. Now days, this narrowing has somewhat been
alleviated by Digital Signal Processing (DSP) within the IF. Through
IF DSP, you [typically] have options to narrow the IF to whatever you
desire. Short of DSP technology, IF filtering by way of a crystal
filtering elements is the desired choice. An outboard DSP unit
connected to your speaker output will not be as effective however,
they are great at reducing heterodynes and general band noise. I
relate this from using DSP units since their introduction to the
amateur services.

A side note..

Regarding:
"a) ICOM FL101 (CW narrow 9mHz IF, 250Hz)"

Somehow, I doubt that they have a 9 millihertz IF. If you're just
cutting and pasting this from another source, then be aware of:

Megahertz is defined as MHz, kilohertz as kHz and hertz as Hz. It is,
in fact, ALWAYS a capital "H" to pay homage to Mr. Heinrich Hertz.
Consider: http://www.ideafinder.com/history/inventors/hertz.htm or,
http://searchnetworking.techtarget.c...214263,00.html
or, http://tf.nist.gov/timefreq/general/glossary.htm (click on "M" or
"J-K" - these folks should know the difference)



Further proof? Take a look at www.fcc.gov and note their frequency
references. In addition, simply take a look at a stereo dial, clock
radio or even your transistor radio and notice how the manufacturers
abbreviate frequency.


Cheers,
Mr. Mentor



"D.K." wrote in message
...
| Hi all,
| I'm considering to upgrade my receiver ICOM R75 with narrow CW
filters. My
| main interest is NDB listening in the LW band.
| There are 2 possiblities:
| a) ICOM FL101 (CW narrow 9mHz IF, 250Hz) + ICOM FL53A (CW narrow
455kHz,
| 250Hz)
| b) INRAD 121 (CW narrow 9010.6kHz, 250Hz) + INRAD 122 (CW narrow
455kHz,
| 250Hz)
| Which combination is the better one in terms of quality and
efficiency.
| Price does'nt matter.
| Any advice is welcome!
| Thanks in advance
|
| D. Kremp
| France
|
|