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weak radio reception. trying to fix. SONY ICF-CD523

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    weak radio reception. trying to fix. SONY ICF-CD523

    Hey all,
    I've got this SONY Under Cabinet Radio. Model # ICF-CD523.
    Over the years the FM reception has really gone down hill. I would like to try and fix this. I opened up the radio and found the FM Chip CXA1960Q. From Pin #18 we go through a 26Ω resistor (R6) and then it goes out to a BPFI (GFWE2 SE). The input of this 3 pin device is fed from a cap (C953, 200pF).
    The other side of this cap goes to the secondary side of the step down transformer. So basically they are using the power cord as an antenna (as it is well known).

    I checked the resistor and the cap, and they are good.
    I can't check the BPFI unless I pull it and test it using a scope and oscilliscope... I'm sure there are other ways.. Anyways...

    Refer to the attched schematic I made up. I basically cut the antenna from going through the transformer. and then soldered in a new wire at the point shown. The wire is then fed through the enclosure and I tried running the wire at different lengths and directions.

    Because the outlet is right behind the radio, I cut 4 feet off the cord.

    Overall, this did improve things... but some stations still have some static.
    But a couple stations do not come in clear. 100.5 for example.
    Other radios in the home play 100.5 quite clear.

    I'm also surprised I can hear 100.5 in the back ground of a 97.5 station.

    Any thoughts... suggestions??
    Do I have my antenna wrong? Or is the chip CXA1960Q semi pooched?


    #2
    Re: weak radio reception. trying to fix. SONY ICF-CD523

    Not sure if this will help....
    Last edited by R_J; 10-25-2014, 09:24 PM.

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      #3
      Re: weak radio reception. trying to fix. SONY ICF-CD523

      worth pointing out that using a power cord as an antenna is going to be worse and worse in the future as more people and company's start using the power line for digital transmission.
      and the ITU i think it is,the international standards group is talking about increasing the allowed power level by something like x30!!!!!

      Comment


        #4
        Re: weak radio reception. trying to fix. SONY ICF-CD523

        For sure.... thats why I cut that feed, and ran my own wire.
        It impoved things.... but the odd station is wacky.

        Comment


          #5
          Re: weak radio reception. trying to fix. SONY ICF-CD523

          Well,, I read through that tech manual. Thats great stuff. Lots of detail.
          I don't have the equipment to do the FM test...
          Is there anything else I cantest or try???

          Comment


            #6
            Re: weak radio reception. trying to fix. SONY ICF-CD523

            do you know the antenna input impedance ?

            because the antenna is going to make a huge difference if it's impedance matched and properly calculated for quarter/half wavelength etc.
            you cant just throw a bit of scap wire around the room and expect good reception across the band.

            Comment


              #7
              Re: weak radio reception. trying to fix. SONY ICF-CD523

              http://www.hamradio.in/circuits/moxon_fm.php

              Comment


                #8
                Re: weak radio reception. trying to fix. SONY ICF-CD523

                I know I can't just run wire all over the place. I read a post on this forum where a guy ran 6.3 feet of wire for an antenna on a similar sony radio. I hooked up 8 feet of wire. Installed the radio where it belongs.... and then started cutting back on the wire until it sounded good. I'm at less than 2 feet. I'll look at that post... and do some research.

                Comment


                  #9
                  Re: weak radio reception. trying to fix. SONY ICF-CD523

                  in doing some research, is a dipole antenna worth trying?
                  I see some for 100.5MHz... which is the station I want to improve. But these antenna's have two wires. Would I ground one? Or is this antenna totally wrong. :O

                  Comment


                    #10
                    Re: weak radio reception. trying to fix. SONY ICF-CD523

                    right idea, but you may need a balun transformer.
                    those used to come fitted to portable tv antenna for example.
                    this is why i asked if you know the input impedence.

                    Comment


                      #11
                      Re: weak radio reception. trying to fix. SONY ICF-CD523

                      I don't know the input impedance. My schematic above shows what I'm dealing with.
                      FM Chip, 26Ω resistor, a band pass filter, cap...and wire.
                      Is there a generic or safe value we can use for the average consumer radio?

                      Comment


                        #12
                        Re: weak radio reception. trying to fix. SONY ICF-CD523

                        the word "safe" only applies to transmitters.
                        with a receiver it just means if you get it wrong, your reception goes to shit.

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