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#9
May 8th 08, 08:04 PM
posted to rec.radio.shortwave
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CW narrow filters
On May 8, 2:51 am, RHF wrote:
On May 7, 7:02 pm, Telamon wrote: In article , RHF wrote: 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 - - - 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 - - . - - No, what I refer to is "Ultimate Rejection : 60 dB & 60 dB = 90 dB". - - This raises the question of how two successive stages - with the figures you provide add up to 90dB? That was my question as well. - - -- - Telamon - Ventura, California Teli - The individual 'piece' versus the Circuit Collective. ~ RHF -fwiw- It was/is poorly stated and a simplistic Analogy; plus Anecdote at best.http://en.wikipedia.org/wiki/Analogy...dotal_evidence -ps- I have moved-on with new "Magic" Numbers ;-} . |
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