40m Pixie kit convert to 70cm

Discussion in 'Homebrew and Kit Projects' started by KN4BSH, Apr 14, 2017.

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  1. KN4BSH

    KN4BSH Ham Member QRZ Page

    I wish I could just find a simple 70cm CW/SSB, 2m CW/SSB or a 6m CW/SSB so I can practice my CW with my friend. I need something very very cost effective.
     
  2. AB5CW

    AB5CW Premium Subscriber QRZ Page

    Is it possible to use the 40M Pixie kits (using a crystal frequency between 7.025-7.125 MHz) to practice with your friend on the air?
     
  3. KN4BSH

    KN4BSH Ham Member QRZ Page

    That is the work around currently - laugh-- just need to find the time to build the kit. I hope for a nice rainy weekend.
     
  4. K9STH

    K9STH Ham Member QRZ Page

    EKU:

    The old F-1 designation is, basically, the same bandwidth as A-1. That is FM without modulation. If you modulate the signal then it can be up to 16 kHz wide depending on the frequency of the modulation, etc. But, just keying the carrier does NOT produce a signal 16 kHz wide!

    If no CTCSS tone is present, and if no audio comes from the microphone, then the signal is just going to be the carrier and then the bandwidth depends on the keying speed just like with a "normal" CW signal. You do not have to disable the modulator, just do not allow microphone audio to get through.

    Glen, K9STH
     
  5. N7EKU

    N7EKU Ham Member QRZ Page

    Aha Glen,

    Which is disabling modulation! Turns out to be very easy to do :) How do you detect it on the other end though? Seems like another HT would not work as just quieting would occur?

    73,


    Mark.
     
  6. VK3YE

    VK3YE Ham Member QRZ Page

    You'd use a separate receiver. A handheld can receive FM. It will go quiet when a nearby CW signal comes up. But listening will be very annoying. You may be able to provide a local signal to act as a BFO but performance will be very poor.

    If you wish to communicate via Morse with a modified handheld you'd be better off to tone modulate with a keyed audio tone (ie F1A pr F2A transmission mode). https://en.wikipedia.org/wiki/Types_of_radio_emissions

    That signal can be received on an unmodified handheld on FM mode and will have a similar range to a voice transmission.

    You'd need to prearrange such contacts and use the FM simplex part of the band.
     
    K6CLS likes this.
  7. K6CLS

    K6CLS Ham Member QRZ Page

    Finally, the right answer. Thanks
     
  8. N7EKU

    N7EKU Ham Member QRZ Page

    Ah,

    Or you could just press PTT and go "beeee be beeee bee beee beee be beee" ;) Well we were speaking about reducing the bandwidth for awhile as I thought there was a question about modifying an HT. But this mode would essentially be just like speaking into the mike.

    I assume, in order to avoide all the delays etc from pressing PTT all the time, that PTT would be used like an old-fashioned send-receive switch: pressed at the beginning of a message, and released at the end after the CW procedural "over" K or KN is sent. Then near the mic you would arrange the speaker of your code practice oscillator. This would take no modification and would be easy to do (you get your sidetone this way too).

    73 and have fun :)


    Mark.
     
  9. VK3YE

    VK3YE Ham Member QRZ Page

    Or you could just send Morse using the DTMF keypad while holding down the PTT. It doesn't matter that it's two rather than one audio frequencies. An external DTMF microphone could be modified with a key connecting across one of the buttons if desired.
     
    N7EKU likes this.
  10. K9STH

    K9STH Ham Member QRZ Page

    EKU:

    Preventing audio from the microphone is not disabling the modulation! Not technically! To really disable the modulation, one has to disable the frequency / phase modulation stage because there can still be noise, etc., superimposed on the carrier by such a stage.

    If one just happened to leave a CTCSS tone on the carrier, then the signal would become MCW and not CW.

    However, just preventing audio from the microphone to happen, the transmitted signal should be pretty "clean".

    Glen, K9STH
     

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