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Re: 455khz filter mods - not sure if it worked

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  • drelectrode
    A couple of things going on today that make it dicey to check sideband. If you re listening to 40M, the band is very open and it is the weekend of a big Ham
    Message 1 of 11 , Feb 9, 2013
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      A couple of things going on today that make it dicey to check sideband. If you're listening to 40M, the band is very open and it is the weekend of a big Ham contest. So between the two things, the band is super packed and will overload even a healthy receiver if it doesn't have very tight IF filtering.

      Are you able to hear any signals at all that you can copy clearly?



      Larry

      --- In RADIOSHACKDX394@yahoogroups.com, "jchajecki" wrote:
      >
      > I've just completed the 455khz filter mod as per Monitor Internet. I've also replaced the two electrolytics C131 and C161. The 455khz mod was supposed to reduce crosstalk but I'm not sure whether it succeeded or has made things worse.
      >
      > When I'm listening on SSB or CW I sometimes seem to be getting two or three signals at a time and its sometimes difficult to pick out a specific signal. Having said that I seem to be be picking up both sides of the conversation more freqently than I used to and a lot of refrences to 'contest'.
      >
      > I've double checked to ensure that I have wired everyting correctly and as far as I can tell, I have done the mod correctly.
      >
      > I'm not sure whther the receiver has become more sensitive, whether it is busy out there tonight (contast?) or whether there is a problem. Can anyone tell me if this is normal after this mod, should be concerned or even go as far as removing the components?
      >
    • jchajecki
      Larry, Yes I can copy signals quite clearly and the contest being in progress might explain it. Seems a bit quieter today.
      Message 2 of 11 , Feb 10, 2013
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        Larry,

        Yes I can copy signals quite clearly and the contest being in progress might explain it. Seems a bit quieter today.


        --- In RADIOSHACKDX394@yahoogroups.com, "drelectrode" wrote:
        >
        > A couple of things going on today that make it dicey to check sideband. If you're listening to 40M, the band is very open and it is the weekend of a big Ham contest. So between the two things, the band is super packed and will overload even a healthy receiver if it doesn't have very tight IF filtering.
        >
        > Are you able to hear any signals at all that you can copy clearly?
        >
        >
        >
        > Larry
      • Tom Holden
        This mod improves the stop-band attenuation of signals 10-50 kHz away from the tuned frequency. A simple before-after test is to tune to a strong local AM-MW
        Message 3 of 11 , Feb 10, 2013
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          This mod improves the stop-band attenuation of signals 10-50 kHz away from
          the tuned frequency. A simple before-after test is to tune to a strong local
          AM-MW station to identify the program and then tune off either side of it by
          that range to see if you can still hear the program (provided there are no
          interfering signals). This is best done in the daytime when the propagation
          is pretty stable and consistent from day to day and nighttime interference
          is not a problem.

          Tom
        • Ernie Rice
          Where can I find this mod? Ernie Sent from my iPhone ... [Non-text portions of this message have been removed]
          Message 4 of 11 , Feb 10, 2013
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            Where can I find this mod?

            Ernie

            Sent from my iPhone

            On Feb 10, 2013, at 14:17, "Tom Holden" <ve3meo@...> wrote:

            > This mod improves the stop-band attenuation of signals 10-50 kHz away from
            > the tuned frequency. A simple before-after test is to tune to a strong local
            > AM-MW station to identify the program and then tune off either side of it by
            > that range to see if you can still hear the program (provided there are no
            > interfering signals). This is best done in the daytime when the propagation
            > is pretty stable and consistent from day to day and nighttime interference
            > is not a problem.
            >
            > Tom
            >
            >


            [Non-text portions of this message have been removed]
          • jchajecki
            Ernie, It was on here: http://www.monitor.co.uk/radio-mods/dx-394/dx-394.htm
            Message 5 of 11 , Feb 10, 2013
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              Ernie,

              It was on here:

              http://www.monitor.co.uk/radio-mods/dx-394/dx-394.htm


              --- In RADIOSHACKDX394@yahoogroups.com, Ernie Rice wrote:
              >
              > Where can I find this mod?
              >
              > Ernie
              >
              > Sent from my iPhone
            • Ernie Rice
              Great! I am going to look it up Ernie Sent from my iPhone ... [Non-text portions of this message have been removed]
              Message 6 of 11 , Feb 10, 2013
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                Great! I am going to look it up

                Ernie

                Sent from my iPhone

                On Feb 10, 2013, at 16:11, "jchajecki" <yahoog@...> wrote:

                > Ernie,
                >
                > It was on here:
                >
                > http://www.monitor.co.uk/radio-mods/dx-394/dx-394.htm
                >
                > --- In RADIOSHACKDX394@yahoogroups.com, Ernie Rice wrote:
                > >
                > > Where can I find this mod?
                > >
                > > Ernie
                > >
                > > Sent from my iPhone
                >
                >


                [Non-text portions of this message have been removed]
              • Ernie Rice
                Pops can t do that one because I don t have any surface mount tools to remove SMTs Is there anyone that can do it for me on the list? Ernie Sent from my iPhone
                Message 7 of 11 , Feb 10, 2013
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                  Pops can't do that one because I don't have any surface mount tools to remove SMTs
                  Is there anyone that can do it for me on the list?

                  Ernie



                  Sent from my iPhone

                  On Feb 10, 2013, at 16:11, "jchajecki" <yahoog@...> wrote:

                  > Ernie,
                  >
                  > It was on here:
                  >
                  > http://www.monitor.co.uk/radio-mods/dx-394/dx-394.htm
                  >
                  > --- In RADIOSHACKDX394@yahoogroups.com, Ernie Rice wrote:
                  > >
                  > > Where can I find this mod?
                  > >
                  > > Ernie
                  > >
                  > > Sent from my iPhone
                  >
                  >


                  [Non-text portions of this message have been removed]
                • Tom H
                  IF: CROSSTALK (Cathell) 03.01.18 Better suppression of bleedthrough (not splatter) of strong signals 10-30 kHz away from frequency tuned. Tack on 2 ceramic
                  Message 8 of 11 , Feb 10, 2013
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                    IF: CROSSTALK
                    (Cathell)
                    03.01.18

                    Better suppression of bleedthrough (not splatter) of strong signals
                    10-30 kHz away from frequency tuned.

                    Tack on 2 ceramic capacitors

                    RADIOSHACKDX394

                    <http://groups.yahoo.com/group/RADIOSHACKDX394/files/Mods/DX-394_mods_Fr\
                    ankCathell.htm>
                    www.mods.dk <http://www.mods.dk/view.php?ArticleId=1843> monitor.co.uk
                    <http://monitor.co.uk/radio-mods/dx-394/dx-394-455khz-if-mods.htm> -
                    msg#3316 <http://groups.yahoo.com/group/RADIOSHACKDX394/message/3316>
                    Ernie, you don't have to remove any devices for the Crosstalk or
                    Bleedthrough mod. Rather you add disc ceramic caps with leads. The above
                    table (if it comes through) is extracted from the Master Index of Mods.
                    You'll find it, along with many others for the 394's IF chain in the IF
                    section (where else!).
                    Tom ve3meo


                    [Non-text portions of this message have been removed]
                  • jchajecki
                    Tom, Thanks, I will give that a go at the next daytime opportunity.
                    Message 9 of 11 , Feb 11, 2013
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                      Tom,

                      Thanks, I will give that a go at the next daytime opportunity.
                    • jchajecki
                      I started work on the final mod this weekend - Noise Blanker Mods - and realised that I did mix up two capacitors, 102 and 104 (100pF and 10nF). I ve now
                      Message 10 of 11 , Feb 18, 2013
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                        I started work on the final mod this weekend - Noise Blanker Mods - and realised that I did mix up two capacitors, 102 and 104 (100pF and 10nF). I've now swapped them around to where they should be.

                        I did the test you suggested and even on a strong station like BBC World Service (7 - 9 on the scale) I get no bleedthrough 10khz either side.

                        I've now completed all the mods (except DSP and DRM and painting the knobs). In the context of a budget priced receiver such as the RX394 I didn't expect them to make a startling difference, but I believe that overall the Radio has been improved and is more useable. SSB reception for example was always distorted, but I can now pick up signals quite clearly. CW signals are also easier to pick put. The audio mods have improved the sound quality especially when an external lodspeaker is attached. I am grateful to the author for sharing them.

                        Regarding the DSP and DRM mod, but since I spent £60 on the receiver, it seemed dispropportionate to spending another £100 or so each to purchase the DSP and DRM boards. I figured that would be better saved towards a better receiver...



                        --- In RADIOSHACKDX394@yahoogroups.com, "Tom Holden" <ve3meo@...> wrote:
                        >
                        > This mod improves the stop-band attenuation of signals 10-50 kHz away from
                        > the tuned frequency. A simple before-after test is to tune to a strong local
                        > AM-MW station to identify the program and then tune off either side of it by
                        > that range to see if you can still hear the program (provided there are no
                        > interfering signals). This is best done in the daytime when the propagation
                        > is pretty stable and consistent from day to day and nighttime interference
                        > is not a problem.
                        >
                        > Tom
                        >
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