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#1
May 6th 08, 04:28 PM
posted to rec.radio.shortwave
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CW narrow filters
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. |
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#2
May 6th 08, 10:41 PM
posted to rec.radio.shortwave
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CW narrow filters
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#3
May 7th 08, 06:08 AM
posted to rec.radio.shortwave
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CW narrow filters
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 ~ RHF . I suppose, but the AR7030 only switches the last filter. And wouldn't that be 120dB ultimate rejection? Here is my attempt as measuring the Kenwood CW filter in my 7030: http://www.lazygranch.com/images/radio/cwfilter.gif After a while, the signal was in the noise. Granted, I don't recall exactly how I did the measurement. I used a RF generator that has 1Hz steps, which is what you need for the crystal filter because it is very sharp. I used a HP8903 to measure the audio level. I used the speaker output because at the time I didn't have a DIN connector to use the line output. I suppose I should have cranked up the RF to the point where the 7030 preamp isn't used. That would push the noise floor to the minimum. While we are at it, why not a filter to roll off the MW and above. |
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#4
May 7th 08, 06:38 AM
posted to rec.radio.shortwave
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CW narrow filters
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#5
May 7th 08, 05:09 PM
posted to rec.radio.shortwave
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CW narrow filters
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 |
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#6
May 7th 08, 11:12 PM
posted to rec.radio.shortwave
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CW narrow filters
RHF wrote:
On May 6, 10:38 pm, Telamon 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 . RHF, As far as I know there is no general method that allows you to combine shape factors for two filters into a number describing the net result. I also know of no general method for combining rejection of two filters to give a meaningful net number. So, please tell us how you arrive at these numbers. |
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#7
May 7th 08, 06:47 PM
posted to rec.radio.shortwave
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CW narrow filters
On May 6, 10:08*pm, 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 ~ RHF . - I suppose, but the AR7030 only switches the last filter. The Icom IC-R75 allows both the 1st and 2nd IF Filters to be switched. - And wouldn't that be 120dB ultimate rejection? In a perfect Circuit yes. Here is my attempt as measuring the Kenwood CW filter in my 7030: http://www.lazygranch.com/images/radio/cwfilter.gif After a while, the signal was in the noise. Granted, I don't recall exactly how I did the measurement. I used a RF generator that has 1Hz steps, which is what you need for the crystal filter because it is very sharp. I used a HP8903 to measure the audio level. I used the speaker output because at the time I didn't have a DIN connector to use the line output. I suppose I should have cranked up the RF to the point where the 7030 preamp isn't used. That would push the noise floor to the minimum. - While we are at it, why not a filter to roll off the MW and above. IIRC - Some Shortwave Radio & Receivers use a Tuned Front End or Limit Band Pass Filters that Block Out of Band Frequencies The Grundig Satellit 800 Millennium Radio comes to mind : HPF & LPF & BPF & SW Switching BPF & FM Tracking Filter http://ph.groups.yahoo.com/group/Sat.../view/17ab?b=9 http://ph.groups.yahoo.com/group/Sat...ab?b=7&m=f&o=0 |
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#8
May 9th 08, 05:18 AM
posted to rec.radio.shortwave
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CW narrow filters
On May 7, 10:47 am, RHF wrote:
On May 6, 10:08 pm, 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 ~ RHF . - I suppose, but the AR7030 only switches the last filter. The Icom IC-R75 allows both the 1st and 2nd IF Filters to be switched. - And wouldn't that be 120dB ultimate rejection? In a perfect Circuit yes. Here is my attempt as measuring the Kenwood CW filter in my 7030: http://www.lazygranch.com/images/radio/cwfilter.gif After a while, the signal was in the noise. Granted, I don't recall exactly how I did the measurement. I used a RF generator that has 1Hz steps, which is what you need for the crystal filter because it is very sharp. I used a HP8903 to measure the audio level. I used the speaker output because at the time I didn't have a DIN connector to use the line output. I suppose I should have cranked up the RF to the point where the 7030 preamp isn't used. That would push the noise floor to the minimum. - While we are at it, why not a filter to roll off the MW and above. IIRC - Some Shortwave Radio & Receivers use a Tuned Front End or Limit Band Pass Filters that Block Out of Band Frequencies The Grundig Satellit 800 Millennium Radio comes to mind : HPF & LPF & BPF & SW Switching BPF & FM Tracking Filterhttp://ph.groups.yahoo.com/group/Satellit800/photos/view/17ab?b=9http://ph.groups.yahoo.com/group/Satellit800/photos/view/17ab?b=7&m=f... . The AR7030 uses a HPF once you are above the MW band. I don't know about the latest versions, but my old 7030 switches in the HPF inside the MW band. That is, it was designed before the band was expanded. The beacon band is low enough that you could probably roll your own LPF ladder filter with reasonable success. Yet another project.... |
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