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About a narrow filter at 10.7 MHz
Hello,
I am designing a radio receiver and I need a narrow filter in the FI stage, at 10.7 MHz, in order to filter a single carrier. Anybody could tell me where to get information about designing ladder filters? Thanks :) |
About a narrow filter at 10.7 MHz
Free crystal filter design software he
http://www.aade.com/filter.htm Joe W3JDR "ForçaCelta" wrote in message oups.com... Hello, I am designing a radio receiver and I need a narrow filter in the FI stage, at 10.7 MHz, in order to filter a single carrier. Anybody could tell me where to get information about designing ladder filters? Thanks :) |
About a narrow filter at 10.7 MHz
=?iso-8859-1?B?Rm9y52FDZWx0YQ==?= ) writes:
Hello, I am designing a radio receiver and I need a narrow filter in the FI stage, at 10.7 MHz, in order to filter a single carrier. Anybody could tell me where to get information about designing ladder filters? Thanks :) It depends on what you need. Don't forget that the first single signal selectivity came to receivers in the thirties, via a single crystal filter. I'm suddenly blank about the name, but it was a balanced transformer feeding a crystal on one side and a trimmer capacitor on the other. You'd trim out the crystal holder's capacitance with the trimmer. Not perfect skirt, but really great selectivity. Later, variants would appear where load resistors were added to broaden the selectivity for voice. Much later, you'd see them cascaded, to improve the skirt. Their big benefit is that you don't have to have more than one crystal frequency, up till ladder filters started making a mark some years back, crystal filters all tended to use crystals separated in frequency by about the required bandwidth. So you'd see these cascaded filters as add-ons, and in the age of solid state, the balanced transformer was replaced with a transistor, with the collector and emitter acting as the two sides of the output winding to drive the crystal and variable capacitor. For sloppy selectivity, there has been lots about just putting a crystal or ceramic resonator in the cathode of a tube or emitter of a transistor. I'm sure for many applications, that would work fine, and doesn't requre any fussing. Michael VE2BVW |
About a narrow filter at 10.7 MHz
"Michael Black" wrote in message ... =?iso-8859-1?B?Rm9y52FDZWx0YQ==?= ) writes: Hello, It depends on what you need. Don't forget that the first single signal selectivity came to receivers in the thirties, via a single crystal filter. I'm suddenly blank about the name, but it was a balanced transformer feeding a crystal on one side and a trimmer capacitor on the other. You'd trim out the crystal holder's capacitance with the trimmer. Lamb? WAG. Pete |
About a narrow filter at 10.7 MHz
On Sun, 17 Jun 2007 12:21:06 -0400, Uncle Peter wrote:
"Michael Black" wrote in message ... =?iso-8859-1?B?Rm9y52FDZWx0YQ==?= ) writes: Hello, It depends on what you need. Don't forget that the first single signal selectivity came to receivers in the thirties, via a single crystal filter. I'm suddenly blank about the name, but it was a balanced transformer feeding a crystal on one side and a trimmer capacitor on the other. You'd trim out the crystal holder's capacitance with the trimmer. Lamb? WAG. IIRC, that's what the BC-348 employed. My BC-348 has several inspection stampings dating to circa 1938-39. 73 Jonesy W3DHJ -- Marvin L Jones | jonz | W3DHJ | linux 38.24N 104.55W | @ config.com | Jonesy | OS/2 *** Killfiling google posts: http://jonz.net/ng.htm |
About a narrow filter at 10.7 MHz
ForçaCelta wrote:
Hello, I am designing a radio receiver and I need a narrow filter in the FI stage, at 10.7 MHz, in order to filter a single carrier. Anybody could tell me where to get information about designing ladder filters? Thanks :) The latest ARRL handbook comes to mind. Have you web searched? It is often profitable to choose a frequency at which you can get lots of inexpensive crystals -- it's often cheaper to buy and sort through a bag of 50 cheap crystals than it is to order four custom made ones, unless you're counting the value of your time. And if you _are_ counting the value of your time, you'll just want to buy a crystal filter, or a whole dang radio! -- Tim Wescott Wescott Design Services http://www.wescottdesign.com Do you need to implement control loops in software? "Applied Control Theory for Embedded Systems" gives you just what it says. See details at http://www.wescottdesign.com/actfes/actfes.html |
About a narrow filter at 10.7 MHz
"Uncle Peter" ) writes:
"Michael Black" wrote in message ... =?iso-8859-1?B?Rm9y52FDZWx0YQ==?= ) writes: Hello, It depends on what you need. Don't forget that the first single signal selectivity came to receivers in the thirties, via a single crystal filter. I'm suddenly blank about the name, but it was a balanced transformer feeding a crystal on one side and a trimmer capacitor on the other. You'd trim out the crystal holder's capacitance with the trimmer. Lamb? WAG. Certainly it was described first by Lamb, or he actualy came up with it, in that famous 1930's article about improving receivers. Basically a phasing crystal filter, which I suddenly was blank about when I posted. I'm not sure I've ever seen it called a "Lamb filter", though perhaps if you go far enough back in the books, it was once called that. Michael VE2BVW |
About a narrow filter at 10.7 MHz
"Uncle Peter" ) writes: "Michael Black" wrote in message ... =?iso-8859-1?B?Rm9y52FDZWx0YQ==?= ) writes: Hello, It depends on what you need. Don't forget that the first single signal selectivity came to receivers in the thirties, via a single crystal filter. I'm suddenly blank about the name, but it was a balanced transformer feeding a crystal on one side and a trimmer capacitor on the other. You'd trim out the crystal holder's capacitance with the trimmer. Lamb? WAG. Certainly it was described first by Lamb, or he actualy came up with it, in that famous 1930's article about improving receivers. Basically a phasing crystal filter, which I suddenly was blank about when I posted. I'm not sure I've ever seen it called a "Lamb filter", though perhaps if you go far enough back in the books, it was once called that. Michael VE2BVW Actually, it wasn't. Don't recognize the famous 1930's article you refer to, but Lamb came up with the Lamb noise blanker. The principle of operation being to turn off the IF strip while the noise pulse was present, the "hole" being less noticeable and annoying than a huge noise spike. Walter Cady came up with the single crystal filter in 1922. Incorporated in most superhets during the years 1925 until the ladder, half lattice and full lattice filters came along in the 60's. W4ZCB |
About a narrow filter at 10.7 MHz
"Harold E. Johnson" ) writes:
"Uncle Peter" ) writes: "Michael Black" wrote in message ... =?iso-8859-1?B?Rm9y52FDZWx0YQ==?= ) writes: Hello, It depends on what you need. Don't forget that the first single signal selectivity came to receivers in the thirties, via a single crystal filter. I'm suddenly blank about the name, but it was a balanced transformer feeding a crystal on one side and a trimmer capacitor on the other. You'd trim out the crystal holder's capacitance with the trimmer. Lamb? WAG. Certainly it was described first by Lamb, or he actualy came up with it, in that famous 1930's article about improving receivers. Basically a phasing crystal filter, which I suddenly was blank about when I posted. I'm not sure I've ever seen it called a "Lamb filter", though perhaps if you go far enough back in the books, it was once called that. Michael VE2BVW Actually, it wasn't. Don't recognize the famous 1930's article you refer to, but Lamb came up with the Lamb noise blanker. The principle of operation being to turn off the IF strip while the noise pulse was present, the "hole" being less noticeable and annoying than a huge noise spike. Walter Cady came up with the single crystal filter in 1922. Incorporated in most superhets during the years 1925 until the ladder, half lattice and full lattice filters came along in the 60's. The QST article is pretty famous, and at the very least is credited with bringing single signal selectivity to amateur radio (if not the world). I can't find a paper reference, but it might be an article titled something like "What's Wrong with our Present Receivers" from 1932 (though I thought the specific article had come later), and it may be referenced in Byron Goodman's January 1957 article of the same name. Everyone credits the article with bringing single selectivity to amateur radio, and I can immediately find some web references that claim (and I've read this somewhere in the paper literature) that Millen used many of the ideas in the article for the HRO receiver. The noise blanker may have been described in the same article. And of course, it was lattice and half lattice filters that came along in the fifties that allowed many to build SSB transmitters, if they couldn't afford mechanical filters and didn't want to use phasing. I never saw a reference to ladder filters (except for some oddball bit in the SSB column in the fifties that had two serial crystals and one going to ground where they joined) until the seventies, and it was more like a decade later before they became popular in hobby circles. Michael VE2BVW |
About a narrow filter at 10.7 MHz
It depends on what you need. Don't forget that the first single
signal selectivity came to receivers in the thirties, via a single crystal filter. I'm suddenly blank about the name, but it was a balanced transformer feeding a crystal on one side and a trimmer capacitor on the other. You'd trim out the crystal holder's capacitance with the trimmer. Lamb? WAG. Certainly it was described first by Lamb, or he actualy came up with it, in that famous 1930's article about improving receivers. Basically a phasing crystal filter, which I suddenly was blank about when I posted. I'm not sure I've ever seen it called a "Lamb filter", though perhaps if you go far enough back in the books, it was once called that. Michael VE2BVW Actually, it wasn't. Don't recognize the famous 1930's article you refer to, but Lamb came up with the Lamb noise blanker. The principle of operation being to turn off the IF strip while the noise pulse was present, the "hole" being less noticeable and annoying than a huge noise spike. Walter Cady came up with the single crystal filter in 1922. Incorporated in most superhets during the years 1925 until the ladder, half lattice and full lattice filters came along in the 60's. W4ZCB The QST article is pretty famous, and at the very least is credited with bringing single signal selectivity to amateur radio (if not the world). I can't find a paper reference, but it might be an article titled something like "What's Wrong with our Present Receivers" from 1932 (though I thought the specific article had come later), and it may be referenced in Byron Goodman's January 1957 article of the same name. Everyone credits the article with bringing single selectivity to amateur radio, and I can immediately find some web references that claim (and I've read this somewhere in the paper literature) that Millen used many of the ideas in the article for the HRO receiver. The noise blanker may have been described in the same article. And of course, it was lattice and half lattice filters that came along in the fifties that allowed many to build SSB transmitters, if they couldn't afford mechanical filters and didn't want to use phasing. I never saw a reference to ladder filters (except for some oddball bit in the SSB column in the fifties that had two serial crystals and one going to ground where they joined) until the seventies, and it was more like a decade later before they became popular in hobby circles. Michael VE2BVW Jeepers. This thread is getting as long as some of Cecils threads. I hope it isn't as dumbfounding. James Lamb, 3CEI, 1CEI and W1CEI, was tech editor for QST in the 30's. As such, unlike todays offerings, he ALWAYS had at least one technical article in each issue starting as early as March 1928. One of those articles was in June 1932 and was titled "What's wrong with our CW receivers?" That article had to do with audio selectivity and no crystal filter was mentioned. In August 1932, he published another article, "Short Wave selectivity to match present conditions". This was amateur radios first published introduction to the single signal crystal filter In this latter article, Lamb acknowledges the pioneering work of Cady in a footnote, who published his discovery and design of the single signal crystal filter in the Proceedings of the IRE over 10 years earlier in April 1922. Lamb only repeated Cadys work in QST. He may have brought it to the amateur fraternity, but the world knew of it from the Proc of the IRE some 10 years earlier. Lamb WAS responsible for the invention of the "Lamb noise silencer" which bears his name some years later. W4ZCB |
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