John Wilke K9RZZ
03-15-2007, 11:19 PM
For the last couple of years, I've been using this old Stereo pulled from my '92 Subaru wagon. It's been a solid performer, and I've never really had any complaints with what it hears, but maybe, just maybe, I could make it better?
In my web readings, there are passing mention of this being done, but no real discussion of it. The challenge is on! After all, the radio was free, right?
I took my time, and it's sort of like a 3D jigsaw puzzle with all the circuit boards stacked and fitted into each other with circuit board connectors. Here's what it looks like when all apart:
http://members.aol.com/j999w/SUB1.jpg
Carefully seaching the boards reveals the ceramic filters (CF151 and CF152):
http://members.aol.com/j999w/SUB2.jpg
The question now is, what are the specs on the filters? Can I improve on them?
Bruce Carter has a nice web page that has lots of information:
http://www.geocities.com/rbrucecarter/ceramic_filter.htm
Searching here indicates that these are probably are Murata:
E10.7JA SFE10.7MJA10-A 150 360 (300) (4.5)
E10.7L SFE10.7ML-A 280 700 (610) 9 (7)
E10.7M SFE10.7MM-A 230 600 (510) 11 (9)
E10.7P SFE10.7MP3-A 250 650 (550) 10 (8)
E10.7S left dot SFE10.7MS2-A 230 570 (420) 6 (4)
E10.7S left dot SFE10.7MS2G-A 230 600 (420) 7 (4.5)
E10.7S right dot SFE10.7MS3-A 180 520 (380) 7 (4.5)
E10.7S right dot SFE10.7MS3G-A 180 520 (380) 7 (5)
So if this receiver has two filters of 180khz and 150khz, I can probably improve on it's selectivity a bit by installing two new SNR filters of 150khz and 110khz. Hopefully that's enough to hear a difference.
It won't be real easy because the solder connections are really wedged in there ...
http://members.aol.com/j999w/SUB3.jpg
So I sharpened up the tip on the soldering iron and _carefully_ removed them, trying not to burn up those little surface mounted capacitors. The filter on the edge of the board I actually broke when removing it. So to get the new ones in, I used a dremel tool to cut the edge away and give me plenty of room to get them in there.
http://members.aol.com/j999w/SUB4.jpg
DONE! I cross my fingers and _carefully_ put it back together. I was quite pleased when I turned it on and heard sound comming out of the speakers!
http://members.aol.com/j999w/SUB5.jpg
Recall that I never really had any complaints about the radio before, but is it any better now?
YES! :D
I have a local on 88.1mhz and have never even heard anything on 88.3 due to the slop. Tuning to 88.3 now reveals WFEN in Rockford, IL., 8kw 75 miles away! 101.9 reveals Chicago's WTMX, 4kw, 75 miles away which I've never heard before due to splatter from my LOUD local on 102.1. (audio clips below)
Total cost of this modification was about 2 hours of time, $2 in parts, and I've logged 2 new stations that I've never heard before during any kind of opening.
Well worth it in my opinion!
;)
John K9RZZ
Milwaukee
In my web readings, there are passing mention of this being done, but no real discussion of it. The challenge is on! After all, the radio was free, right?
I took my time, and it's sort of like a 3D jigsaw puzzle with all the circuit boards stacked and fitted into each other with circuit board connectors. Here's what it looks like when all apart:
http://members.aol.com/j999w/SUB1.jpg
Carefully seaching the boards reveals the ceramic filters (CF151 and CF152):
http://members.aol.com/j999w/SUB2.jpg
The question now is, what are the specs on the filters? Can I improve on them?
Bruce Carter has a nice web page that has lots of information:
http://www.geocities.com/rbrucecarter/ceramic_filter.htm
Searching here indicates that these are probably are Murata:
E10.7JA SFE10.7MJA10-A 150 360 (300) (4.5)
E10.7L SFE10.7ML-A 280 700 (610) 9 (7)
E10.7M SFE10.7MM-A 230 600 (510) 11 (9)
E10.7P SFE10.7MP3-A 250 650 (550) 10 (8)
E10.7S left dot SFE10.7MS2-A 230 570 (420) 6 (4)
E10.7S left dot SFE10.7MS2G-A 230 600 (420) 7 (4.5)
E10.7S right dot SFE10.7MS3-A 180 520 (380) 7 (4.5)
E10.7S right dot SFE10.7MS3G-A 180 520 (380) 7 (5)
So if this receiver has two filters of 180khz and 150khz, I can probably improve on it's selectivity a bit by installing two new SNR filters of 150khz and 110khz. Hopefully that's enough to hear a difference.
It won't be real easy because the solder connections are really wedged in there ...
http://members.aol.com/j999w/SUB3.jpg
So I sharpened up the tip on the soldering iron and _carefully_ removed them, trying not to burn up those little surface mounted capacitors. The filter on the edge of the board I actually broke when removing it. So to get the new ones in, I used a dremel tool to cut the edge away and give me plenty of room to get them in there.
http://members.aol.com/j999w/SUB4.jpg
DONE! I cross my fingers and _carefully_ put it back together. I was quite pleased when I turned it on and heard sound comming out of the speakers!
http://members.aol.com/j999w/SUB5.jpg
Recall that I never really had any complaints about the radio before, but is it any better now?
YES! :D
I have a local on 88.1mhz and have never even heard anything on 88.3 due to the slop. Tuning to 88.3 now reveals WFEN in Rockford, IL., 8kw 75 miles away! 101.9 reveals Chicago's WTMX, 4kw, 75 miles away which I've never heard before due to splatter from my LOUD local on 102.1. (audio clips below)
Total cost of this modification was about 2 hours of time, $2 in parts, and I've logged 2 new stations that I've never heard before during any kind of opening.
Well worth it in my opinion!
;)
John K9RZZ
Milwaukee