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#21
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Download RFSim99 and let it do it for you. Download Filter Design
from AADE's site and let it do it for you. Download NuHertz's demo version of their filter design software and let it do it for you. There may even be web aplets that will do it for you. And then you can play with configurations and shape factors and the inevitable tradeoffs between complexity and shape factor. Cheers, Tom Paul Burridge wrote in message . .. Hi all, I need a simple design for a BPF with a centre frequency of 17.2Mhz., corner frequencies one Meg or therabouts either side of that and a reasonably good shape factor (nothing critical here). I don't mind having to do a bit of tweaking of values myself if anyone has something close to that they can post. Passive L/C combinations only, please. (assume the usual 50R nominal Zs.) Thanks, p. |
#22
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For a very simple bandpass design program download program BANDPAS1 from
website below. Also obtain response versus frequency. Download in a few seconds and run immediately. -- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
#23
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For a very simple bandpass design program download program BANDPAS1 from
website below. Also obtain response versus frequency. Download in a few seconds and run immediately. -- .................................................. .......... Regards from Reg, G4FGQ For Free Radio Design Software go to http://www.btinternet.com/~g4fgq.regp .................................................. .......... |
#24
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On Thu, 04 Mar 2004 17:58:26 -0800, John Larkin wrote:
On Thu, 04 Mar 2004 23:43:21 +0000, Paul Burridge wrote: Hi all, I need a simple design for a BPF with a centre frequency of 17.2Mhz., corner frequencies one Meg or therabouts either side of that and a reasonably good shape factor (nothing critical here). wtf? I don't mind having to do a bit of tweaking of values myself if anyone has something close to that they can post. Passive L/C combinations only, please. (assume the usual 50R nominal Zs.) Thanks, p. The usual technique is to get a book that has tables of normalized LC lowpass filters of various types, pick a response you like, and scale it and map to a bandpass. Williams' "Electronic Filter Design Handbook" has all this stuff. It's mildly tedious, so I won't offer to do one for you. John He already has a book with a fair amount of tables and all the explainations on how to go about the design. I'm wondering WTF here. Hey paul. wtf? -- Best Regards, Mike |
#25
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On Thu, 04 Mar 2004 17:58:26 -0800, John Larkin wrote:
On Thu, 04 Mar 2004 23:43:21 +0000, Paul Burridge wrote: Hi all, I need a simple design for a BPF with a centre frequency of 17.2Mhz., corner frequencies one Meg or therabouts either side of that and a reasonably good shape factor (nothing critical here). wtf? I don't mind having to do a bit of tweaking of values myself if anyone has something close to that they can post. Passive L/C combinations only, please. (assume the usual 50R nominal Zs.) Thanks, p. The usual technique is to get a book that has tables of normalized LC lowpass filters of various types, pick a response you like, and scale it and map to a bandpass. Williams' "Electronic Filter Design Handbook" has all this stuff. It's mildly tedious, so I won't offer to do one for you. John He already has a book with a fair amount of tables and all the explainations on how to go about the design. I'm wondering WTF here. Hey paul. wtf? -- Best Regards, Mike |
#26
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On Fri, 05 Mar 2004 11:28:51 GMT, Active8
wrote: He already has a book with a fair amount of tables and all the explainations on how to go about the design. I'm wondering WTF here. Hey paul. wtf? Fair point. I just wondered if anyone had a design similar to requirements *already* lying around they might post it, that's all. Save me a bit of scrawling and button-pushing. I didn't wish to put anyone out. Thanks to all who responded, BTW. Some very useful steers. -- The BBC: Licensed at public expense to spread lies. |
#27
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On Fri, 05 Mar 2004 11:28:51 GMT, Active8
wrote: He already has a book with a fair amount of tables and all the explainations on how to go about the design. I'm wondering WTF here. Hey paul. wtf? Fair point. I just wondered if anyone had a design similar to requirements *already* lying around they might post it, that's all. Save me a bit of scrawling and button-pushing. I didn't wish to put anyone out. Thanks to all who responded, BTW. Some very useful steers. -- The BBC: Licensed at public expense to spread lies. |
#28
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Hi Paul,
E-mail me directly and let me know how many poles you need. I have the AADE program, and I will be glad to do that for you. Pete "Paul Burridge" wrote in message ... On Fri, 05 Mar 2004 11:28:51 GMT, Active8 wrote: He already has a book with a fair amount of tables and all the explainations on how to go about the design. I'm wondering WTF here. Hey paul. wtf? Fair point. I just wondered if anyone had a design similar to requirements *already* lying around they might post it, that's all. Save me a bit of scrawling and button-pushing. I didn't wish to put anyone out. Thanks to all who responded, BTW. Some very useful steers. -- The BBC: Licensed at public expense to spread lies. |
#29
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Hi Paul,
E-mail me directly and let me know how many poles you need. I have the AADE program, and I will be glad to do that for you. Pete "Paul Burridge" wrote in message ... On Fri, 05 Mar 2004 11:28:51 GMT, Active8 wrote: He already has a book with a fair amount of tables and all the explainations on how to go about the design. I'm wondering WTF here. Hey paul. wtf? Fair point. I just wondered if anyone had a design similar to requirements *already* lying around they might post it, that's all. Save me a bit of scrawling and button-pushing. I didn't wish to put anyone out. Thanks to all who responded, BTW. Some very useful steers. -- The BBC: Licensed at public expense to spread lies. |
#30
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Paul Burridge wrote in message ... Hi all, I need a simple design for a BPF with a centre frequency of 17.2Mhz., corner frequencies one Meg or therabouts either side of that and a reasonably good shape factor (nothing critical here). I don't mind having to do a bit of tweaking of values myself if anyone has something close to that they can post. Passive L/C combinations only, please. (assume the usual 50R nominal Zs.) Thanks, p. -- The BBC: Licensed at public expense to spread lies. The simplest filter that'll get you by, is this one. (a couple of tuned circuits with a bit of top-coupling :-) ... ___ ||C1 -|_R_¦------.----.-------||-------.----.-------, O/p Source |L2 |C2 || |C2 |L2 | I/p | | | | .-. C| --- --- C| | |load R C| --- --- C| |R| C| | | C| '-' | | | | | === === === === === GND GND GND GND GND F1=16.2e6 'lower limit MHz F2=18.2e6 'upper limit MHz R=50 'Ohms source and load impedance Pi=3.142 C1 = (F1+F2) / (4 x Pi x F1 x F2 x R) C2 = F1 /(Pi x F2 x (F2-F1) x R)/2 L2 = 2xR /(4 x Pi) x (1/F1 - 1/F2) The inductors end up being quite small but a couple of loops of wire cost nothing. At 25megs the output is down to about 3% , which is not bad. This particular style is the "3 element" design and from the traditional "Constant K" filter stable. The pleasantly simple to design "constant K's" and associated "M derived" filters, can be easily and freely used for most day-to-day electronics work. Exact Filter design, or 'synthesis' as they nowadays prefer to call it, can be a nightmare if you're coming in from scratch. Even using a filter design programme requires a good knowledge of filter types/performance/spec's before data can begin to be entered. If not using a prog' you move onto the more vexing method of having to design an initial (prototype) low-pass filter, either via precalculated tables or computing the required co-efficients, then mathematically transforming the low-pass values into a bandpass (etc) design. For higher order filters it can be ball-acheing drudgery and even then inductor resistance has a nasty habit of spoiling that pristine work of art. (not a problem with DSP filters). I can't suggest a decent book, as the general purpose books seem over complicated and destined to be written by maths people for maths people. (The old GPO line-comm's manuals have useful notes on the 'K and M ' filters). regards john |
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