i was told if i change the crystal filter in my cob 200...MCF..10L08A filter...would make it recieve better on fm....well make it sound better...is this right?and does anyone no wot crystal to replace with......thanksssss
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crystal...filter...change for better auido recieve????/
- Thread starter frogger
- Start date
I've not heard of that mod, but if I hear anything or see any info that I think is solid, I'll pass it on.
DTB his main problem is that just about everybody over here use wider deviation than they are supposed to,
most of the people frogger talks to use hf sets or a cb with the deviation pot turned up too far,
they will sound ok on some cb's and crap on others especially the newer radios that have a 7 or 8kc crystal filter such as the cobra and magnum 257,
in the past i have either swapped the filter for a 15kc or changed terminating impedance to broaden the filter response,
the same thing would happen back in the 80's when it was crowded on our legal 40ch,
lots of people fitted 15kc crystal filters and found that many people sounded distorted because the terminating impedance for the original 300kc ceramic filter was swamping the crystal filter and making it too narrow,
insert a couple of 1.5 to 1.8k resistors in series with input and output filter legs and the problem was sorted or at least much better than just swapping the filters,
i am not saying changing the filter will definately work but at least the required impedance when changing from the stock cobra filter is much closer than when changing from ceramic to crystal, he may also need to change the 455ht filter for a 8kc from a yaesu 747/840
most of the people frogger talks to use hf sets or a cb with the deviation pot turned up too far,
they will sound ok on some cb's and crap on others especially the newer radios that have a 7 or 8kc crystal filter such as the cobra and magnum 257,
in the past i have either swapped the filter for a 15kc or changed terminating impedance to broaden the filter response,
the same thing would happen back in the 80's when it was crowded on our legal 40ch,
lots of people fitted 15kc crystal filters and found that many people sounded distorted because the terminating impedance for the original 300kc ceramic filter was swamping the crystal filter and making it too narrow,
insert a couple of 1.5 to 1.8k resistors in series with input and output filter legs and the problem was sorted or at least much better than just swapping the filters,
i am not saying changing the filter will definately work but at least the required impedance when changing from the stock cobra filter is much closer than when changing from ceramic to crystal, he may also need to change the 455ht filter for a 8kc from a yaesu 747/840
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