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#1
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20 MURATA CFUM 455 I CERAMIC FILTERS
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#2
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Too bad you don't give the specifcations, you might get a lot more
interest. Terry |
#3
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Well,now I know what filters look like,as pertains to radios
anyway.(staying on topic here,just like I always do) Nederlands,eh? I know of a guy in Nederlands (I get his email newsletters,I can prove that too) who sells genuine World War Two Jeep parts. cuhulin |
#4
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TERRY,
If these Murata 455 Ceramic Filters interest you, then you may wish to take a look at this replacement for a 455 kHz IF Filter. "Channel Guard" RX 455 kHz IF Filter. http://cgi.ebay.com/ws/eBayISAPI.dll...tem=5762938320 * The 455 KHz version is an ultra narrow, 3-pole ceramic filter that replaces the existing (and broader) 1-pole Murata ceramic filter. (It's that small black or gray plastic cube soldered into the main CB chassis.) Just unsolder the old filter, install the 3 CHANNEL GUARD bare wires into the corresponding empty INPUT/OUTPUT/GROUND holes, and connect to +8-13 VDC. You are done! Channel Guard Filter Hook-Up Details http://www.cbcintl.com/docs/cghookup.htm http://www.cbcintl.com/docs/CG455-HOOKUP.pdf = = = wrote: Too bad you don't give the specifcations, you might get a lot more interest. Terry |
#6
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I own a small shirtpocket size Westinghouse AM/FM/Shortwave Radio.About
six years ago,I was listening to it and I laid it down on my couch and I went to my kitchen.When I got up,it slid off my couch and hit the hardwood floor.I think it landed on the on/off/volume control knob when it hit the floor.I removed the chassis from the cabinet and I looked at it.It looks to me like from the shaft (the knob fits on) on back like a sort of a little cube shaped affair and quite a few solder connections where the "cube" was soldered to the radio's circuit board.I know how to solder but such close quarters as that situation is,I don't think I can solder it back together properly.I wouldn't mind snail mailing the radio via UPS to somebody to see if it is worthwhile trying to repair the radio.Of course,when it hit the floor,it might have damaged something else too and it might not be worth fooling with.I would be glad to pay what it's worth to have the radio repaired and shipping and handling charges both ways.I think it is a nice little radio.Or it used to be untill it got broken anyway.I know it's around here somewhere if I can ever find it again.My old house is incredibly full of junk,it's like some of those horror movies y'all see on tv.The radio is in a bag because I didn't put the chassis back in the cabinet. cuhulin |
#7
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Thanks, these look like something I could really use!
Terry |
#8
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I thought those were CFU-455I................that would be a 4kHz bandwidth
with a 455kHz center frequency. The Z in / out would be 2k. Pete wrote in message oups.com... Too bad you don't give the specifcations, you might get a lot more interest. Terry |
#9
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Pete wrote:
Pete KE9OA Apr 14, 12:57 pm show options The Inrad unit would be good. About those Murata filters..........the older Murata databook I have specifies those filters as having a 2k impedance. That is the design spec I have been using for the last several years, and the do work ok with that impedance. The 4k spec seems more in line with the natural impedance of many of the commercially available crystal filters. Pete ---------------------------------------- By 4K I meant BW, I have been using 2K (OK 2010 Ohm metal film, "low noise" Dale mil surplus) for my load. I use a BFO from teh ARRL circuit desing handbook circa 1975. It uses a back to back varicap-diode and a DC voltage for tuning. I use a MOSFET buffer to couple the out put to our HP SA at work. My BFO tunes from 450~460KHz and is very clean. I have a HP DFC and Tektronix scope to verify the Fc. Crude but very stable. The BFO is routed through a emiter follower to give me 50 Ohms and I add a 2K resistor in series. The BFO was from my R392/URR days. That reciever is the little brother to the R390. It has a 455KHZ IF out and I built my own product detector using a motorola balanced modulator. The BFO is all that remains of that project. It is in a metal Sucretes cough drop box and it was too good to toss. Today I use Altoid metal tins for a lot of my projects. The tiny ones make good Reverse & Overvoltage Protection cases because they are RF tight, the larger ones make either good project boxes, or are great for holding sub-modules. It is so much easier to build a "complex" project if the sections can be built and tested individualyu. Plus it makes "major" changes a piece of cake. Build a new whatever module. I am debating building something like the non longer available Kiwa MAP outboard IF strip complete with a good selection of different BW filtters, a stand alone BFO, a synch AM detector would be nice, but I really don't know enough to try to design one from the ground up, and my search efforts have been a mixed bag. A seperate IF strip /detector audio conditioning would be very do-able and this fitler research may well turn into that. I liked Craig's discription of his "tone tilt" tone control, and found a good circuit on a electiic guitar site. They had their's set for 1K, but it was simple to scale the parts to give his 700Hz tilt point, I like it much better then the simple hi-cut, or complex trebble/bass boast HiFi tone controls. I have a couple of mil-surplus 300-2500HZ AF filtes that are very narrow with no ringing. For my needs a outboard detector/etc is looking like a winner. I really only need one "perfect" IF/BFO/Fitler so I could switch between my 2 R2000s and use the standard on board/in radio detector/BFO for back ground monitoring. I am mainly into utility comms and I almost never have to really dig on two freqs at the same time. As to the source and load resitances when using Murata ceramic filters, I have found higher Z sources and lower Z loads improve the skirt. But very much off on either the in or out really ups the loss. Terry |
#10
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Couldn't radios be designed with a "check engine light"? Sort of like on
cars.Just push a few buttons and a digital read out would let you know what is wrong with the radios,whichever part or parts or whatever. cuhulin |
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