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Re: Building the Ensemble RXTX: testing the PA stage

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  • pauldebono@rocketmail.com
    A very jolly, and prosperous new year to all ! Setup: CFGSR tuned on various bands with ptt to activate PA. Frequency of interest: 40-30-20 meters. DL6IAK
    Message 1 of 38 , Dec 30, 2012
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      A very jolly, and prosperous new year to all !

      Setup: CFGSR tuned on various bands with ptt to activate PA.
      Frequency of interest: 40-30-20 meters.
      DL6IAK dual tone oscillator input to line out, jumpers crossed.
      Audigy 2 PCI soundcard.

      Testing the PA output power, across a 50 ohms load, with an RF probe;

      From 1Mhz to 5 Mhz, : between 3.9 v and 5.3 volts.
      On 40m: 9 volts.
      On 30m: 9 volts.
      From 11 Mhz to 13 Mhz: between 8.5 and 5.5 volts.
      On 20m: 4 volts.

      Phasing problems ? doubt it !
      Transformer windings adjustments- probable, but which ?
      Wrong core for the correct frequency range ?
      Effects of crossed jumpers ?
      Effects of T6 reversal ?

      Paul


      --- In softrock40@yahoogroups.com, "pauldebono@..." <pawlud@...> wrote:
      >
      > Alan,
      > I have to rig up again the kits, check the si570 version, have a closer listning in to this annoying mush. It seems it only occures on pic/avr controlled chips. With USB, it seems to be ok, subject to confirmation. At present. I am trying to finish up the testing of the pa stage, and once its ok as SDR, I will start working on a stand alone version. I have another four retired sdr kits, all receivers, and wondered if there is a matching tx only kit to go with these kits.
      >
      > Paul
      >
      > --- In softrock40@yahoogroups.com, "Alan" <alan4alan@> wrote:
      > >
      > >
      > > ----- Original Message -----
      > > Subject: [softrock40] Re: Building the Ensemble RXTX: testing the PA stage
      > >
      > >
      > > > Alan,Give me some time to answer your question, as I am busy with the Ensemble right now.
      > > > However, I do remember that the tuning noise was very noticeable where it was needed most, at the slow tuning rate, in the khz
      > > > range last digits .
      > > >
      > >
      > > Paul,
      > >
      > > It looks like my quick checks recently might be wrong.
      > > I was checking again this morning on what I think was the same setup and found a fair bit of disturbance when tuning the Si570 in 1
      > > Hz steps. The other day I thought this was quite low.
      > > I really do not know what is causing it, maybe the USB pulses.
      > > But it seemed just like before, a bigger jump every 7-8Hz steps.
      > > My interpretation of the Freeze_M is that it was introduced to remove the occasional larger jump which is what I seem to be seeing.
      > > I am wondering if the Si570 can really shift frequency with no detectable disturbance.
      > >
      > > Thinking about the KX3 I realise it is different to other SDRs. It is really direct conversion, the LO is in the centre, carrier
      > > position. Would this be sensitive to these little jumps?
      > >
      > > 73 Alan G4ZFQ
      > >
      >
    • Orin
      ... Oops, I should have said R25... ... You have it right. CFGSR indicates 21.1 MHz, 10kHz single tone into the Line Out input on the RXTX. The image does
      Message 38 of 38 , Jan 1, 2013
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        --- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@...> wrote:


        Oops, I should have said R25...


        >
        > Suggestion: check the polarity on C12.


        ...which would make the associated capacitor C11. It's OK. I even pulled it and tried another. And for good luck, I swapped C15 and C16. No change in behavior.


        >
        > The behavior you describe at R26 is not right. Any differential behavior among the four op amps will cause exactly the symptoms you are showing; modulation by the input audio.
        >
        > Warren Allgyer - W8TOD
        >
        > --- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@> wrote:
        > >
        > >
        > > One of us is confused and there is a high probability it is me. I have been thinking you were using the 10KHz tone on the "Line Out" input to the RXTX. If you do this it should result in a CW carrier at full power, 10 KHz from the CFGSR indicated frequency. It will be either plus or minus 10 KHz depending on the setting of the IQ jumper. If the IQ phase and gain balances are off then you will see the lesser image 10 KHz on the other side and it should null out with gain and phase adjustments. The resulting carrier should be pure, single frequency with no sidebands. There should be no output at all on the CFGSR frequency.


        You have it right. CFGSR indicates 21.1 MHz, 10kHz single tone into the "Line Out" input on the RXTX. The image does null depending on the IQ phase/gain settings.


        > >
        > > Somehow your 10KHz tone is modulating the CFGSR frequency instead of just mixing with it. So what you appear to have is an AM signal centered around the CFGSR frequency with appropriate 10 KHz sidebands, instead of a CW signal at CFGSR +- 10KHz.
        > >
        > > I used that tone generator some time ago but I don't remember the application. I think for such tests you will find that Rocky 3.7 has much more capability and it integrates the PTT, frequency control, and tone generation in one package. As a bonus, Rocky includes a two-tone test generator that allows true IMD measurement.


        Unfortunately, Rocky isn't playing nice with my soundcards on Windows 7. I'll try some more if I get chance tomorrow night.

        Orin.
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