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Thread: Listening to CW

  1. #1

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    Default Listening to CW

    Hi
    I'm trying to listen to some morse on 40 Metres for practice but when ever I find a operator sending a bit slower (15 wpm ish) so I can try and write some down I get other morse operators breaking in . I have a Alinco DX SR9 transceiver which has CWU and CWL settings and a narrow filter but I can't find I can easily hear one station without hearing others. Perhaps this is why people spend a lot more on kit :-)
    Cheers
    Nev

  2. #2
    Super Moderator 5B4AJB's Avatar
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    Maybe you could try building a narrow audio filter, they're pretty good on top of narrow I.F. filters.

    Just had a quick image search on google and there are tons of circuits, I recommend a simple coils & caps' one first, before you go digital.

    Another neat trick I saw once was simply a cardboard tube cut to a particular resonant frequency placed over the speaker!

    [edit] if you're quick, there's a couple of Datong audio filters on ebay starting bid at $1 - I use one myself, in fact it was one of the first bits of kit I ever bought...
    Last edited by 5B4AJB; Fri 12th May 2017 at 08:44.

  3. #3

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    Thanks for your reply 5b4ajb I will have to look into doing that. Would I be correct in thinking that more expensive radios already have these filters ?
    Many thanks
    Nev

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    Super Moderator 5B4AJB's Avatar
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    Modern transceivers usually have audio filter options, basically graphic equalisers for the received and transmitted audio.
    There's no reason you can't add a graphic equaliser to an old valve radio, apart from winding up all the OM

    If your radio has an I.F. shift or other options, see what difference that does to the incoming CW...

  5. #5

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    In the February issue of QST magazine (page 43) there is a great article on how to make a resonant speaker out of PVC pipe for very short money. I haven't tried it but I hope to soon.

    I have encountered the same problem in my listening experience as well. I just figured out this week that the my speaker, just as it is, has a resonant frequency of about 500 Hz. I started out listening with the tone set at 700Hz and that wasn't working for me so I changed the tone to 600Hz. 600Hz was better but I then started moving my rit to a lower frequency where it sounded better. I used an app on my phone to find out what the tone was that I could hear best and I reset my side tone to 500Hz which is much better for my rig. I think this means that my speaker is resonant at 500Hz. My transceiver is an Icom IC718.

    Because your rig has a detachable front face, If you wanted to try something just for the fun of it you could put the face flat on a desk and place a toilet paper tube or paper towel tube on top of the speaker. you can play with the length of the tube and possibly make the tube resonant to the tone you are using. You’ll probably find it very inconvenient to operate the rig with the faceplate flat on the desk top.

    None of these solutions will help with filtering out other signals but it can help make the other signals less significant.

    KC1FLN

  6. #6

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    Hi Clcurtin9 many thanks for the reply. Yes the front of my radio can come off and connect to the back via a Cat5 cable I believe although I haven't done this yet.
    I will Google this article you mentioned and have a look.
    Have a great weekend mate.
    Nev

  7. #7

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    An audio filter can certainly help 'narrow down' a wide pass band, but it's not a very 'good' way of doing it. A better way would be to have a narrower IF stage filter which effectively makes the 'window' your receiver 'sees' a signal through. A narrower 'window' means things beside the desired signal are blocked. Like looking through a peep-hole instead of a picture window, sort of.
    With the receiver in question, the audio route would probably be much easier. No idea if IF stage filtering is even done in it...

  8. #8

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    The audio filter could be very helpful in this case but there are other things to consider. I think you can find helpful tutorials out there to give you the actual steps by steps direction.

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