On May 6, 10:38*pm, Telamon
wrote:
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

Telamon - Did I say it was "Math" ?

Shape Factor : 2.0 (1st IF) and 2.0 (2nd IF) comes out
to roughly 1.4 at the end of the IF Processing Stages
in the Signal Path.

OK so 60 dB was a bad number so make it 85 dB.

Ultimate Rejection : 85 dB (1st IF) and 85 dB (2nd IF)
comes out to roughly 127 dB at the end of the IF
Processing Stages in the Signal Path.

practically speaking - no math required ~ RHF