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#11
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I looked up the specs, they are aweful filters
the 40db bandwidth is around 15kHz,,,ouch !!! wide enough for the kitchen sink ! the LF-D6 filters I use have a 60db bandwidth of 12kHz. "your name here" wrote in message ... check out these filters http://cgi.ebay.com/ws/eBayISAPI.dll...m=5766301 086 |
#12
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Hi Terry,
I understand what you mean now! If you need a Sync detector, I designed one using an Analog Devices AD607 Quadrature I.F. system. A few years back, I also designed a general purpose product detector for boatanchor receivers. With the 600uH I.F. transformer as the L and a varicap diode to tune it, stability is good. The transformer itself has a tuning range of about 380kHz to 650kHz, so it will cover the standard 450 through 500kHz IFs. I like the idea of using separate modules when building receivers..................that is the approach I use when working on a brand new design. If you have a good signal generator, you can use that for LO injection; this way, you can test the RF deck before you get the LO / synthesizer designed. It sounds like you have the right equipment to get it done right. Pete wrote in message ups.com... 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 |
#13
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Wouldn't that be good! Actually, a couple of radios that have that built in
test equipment (BITE) function are the HF-2050, RA6790/GM, and probably a host of others. I like that "check engine light" idea...........just take it to the local diagnostics shop and have them fix it. Pete wrote in message ... 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 |
#14
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Don't forget the Murata CFR series! Too bad Murata stopped making them.
Now, about those LF-D6 filters....................I'll take 500,000 of them. Just kidding! How is that new MD receiver working out? DR333 or something like that? Pete "mike maghakian" wrote in message ... I looked up the specs, they are aweful filters the 40db bandwidth is around 15kHz,,,ouch !!! wide enough for the kitchen sink ! the LF-D6 filters I use have a 60db bandwidth of 12kHz. "your name here" wrote in message ... check out these filters http://cgi.ebay.com/ws/eBayISAPI.dll...m=5766301 086 |
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