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Telamon · May 7th 08, 06:38 AM posted to rec.radio.shortwave

In article
,
wrote:

On May 6, 2:41 pm, RHF wrote:
wrote:
On May 5, 9:41 am, "D.K." wrote:
Hi all, I'm considering to upgrade my receiver ICOM R75 with CW
narrow 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

For my AR7030, I just put in a 250Hz Kenwood crystal filter in
the last IF. Does it really help to change two IF filters?

When I was doing beacons, I followed up with a FFT program
(ARGO). It provides both a narrow band filter (the FFT bin
itself) and a visual manner to see the Morse code.

M... Sushi,

Should not the Two separate IF Filters of the same Band-Width : one
for the 1st IF and one for the 2nd IF create a Series RF Signal
Path resulting in a better combined Filtering Shape Factor then one
along; plus improve the Ultimate Rejection of the RF Signal Path.

Shape Factor : 2.0 & 2.0 = 1.4

Ultimate Rejection : 60 dB & 60 dB = 90 dB

SNIP

That's some very interesting math you got going there.

--
Telamon
Ventura, California