Loading ...
Sorry, an error occurred while loading the content.

Re: Building the Ensemble RXTX: testing the PA stage

Expand Messages
  • warrenallgyer
    Hi Orin If you have ready access to the VNWA then you can tweak the output filter by squeezing (lowers the cutoff frequency) or spreading (raises it) the turns
    Message 1 of 38 , Dec 31, 2012
    View Source
    • 0 Attachment
      Hi Orin

      If you have ready access to the VNWA then you can tweak the output filter by squeezing (lowers the cutoff frequency) or spreading (raises it) the turns on L2 and L3. The tradeoff will be output power on 10 meters. I was able to get the 15 meter second harmonic down to -40 dB this way and still get 800 mw out on 10. If I adjusted for 1 watt on 10 then I could only get the 42 MHz down to about 34-35 dB.

      Warren Allgyer - W8TOD

      --- In softrock40@yahoogroups.com, "Orin" <orin.eman@...> wrote:
      >
      > It just so happens that I put my Ensemble RXTX on the spectrum analyzer
      > this morning. Mine is built for 15-10m. I had tuned the low pass
      > filter for minimum loss, but was rather worried about the 2nd harmonic
      > on 15m. I was right. I need 13dB more attenuation at 42MHz. Here is
      > my VNWA sweep of the filter:
      >
      > 15-10m Filter tuned vs Elsie
      > <https://picasaweb.google.com/lh/photo/Ujjps0q183ySKsaP29mDm4LS1FToz1TiC\
      > JzHAUEj7Cg?feat=directlink>
      >
      > and here are the
      >
      > 15m and 10m spectra.
      > <https://picasaweb.google.com/103209697005891839426/December312012?authu\
      > ser=0&feat=directlink>
      >
      > Even with if my filter matched the theoretical, I'd still need 10dB more
      > attenuation at 42MHz. Perhaps there is something wrong with my PA.
      >
      > Orin,
      > RF hates me.
      >
      >
      > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
      > >
      > > Paul
      > >
      > > A reduction from 16 to 12 turns seems too much. I think you need to be
      > absolutely sure you are transmitting on the frequency you expect.
      > >
      > > It sounds to me like the energy you are measuring is on a higher
      > frequency than 20 meters but that is just a guess. Having to remove one
      > third of the turns to make power just does not sound right to me.
      > >
      > > If you have a general coverage receiver you would do well to tune the
      > signal at the expected frequency and then check it at the second and
      > third harmonic frequencies as well.
      > >
      > > Something is amiss here. You are basically eliminating the low pass
      > filter in the output in order to make power and I fear you may be
      > causing other problems for yourself in doing so.
      > >
      > > Good luck and Happy New Year from Beijing
      > >
      > > Warren Allgyer - W8TOD
      > >
      > > --- In softrock40@yahoogroups.com, "pauldebono@" pawlud@ wrote:
      > > >
      > > > Warren,
      > > >
      > > > All components are correct as per building notes for 40-30-20
      > meters.
      > > >
      > > > At T4, the output is 10 volts on 20 meters !
      > > >
      > > > The output goes down to 4 volts at C25.
      > > >
      > > > C25, 470pf was checked-ok.
      > > >
      > > > Reduced turns on L2 from 16 turns to 12 turns, and bang, 10 volts on
      > all bands !
      > > >
      > > > But, still 4 volts at output on 20 meters, so I am experimenting
      > with reducing L3 as well !
      > > >
      > > > Paul
      > > >
      > > >
      > > > --- In softrock40@yahoogroups.com, "pauldebono@" wrote:
      > > > >
      > > > > Warren,
      > > > > Thanks for the advise. I will be checking them all.
      > > > >
      > > > > Before going throu the checks, I am also thinking about
      > disconnecting L1 and inject a 14Mhz signal into C21, as much has been
      > said about T2 !
      > > > >
      > > > > Paul
      > > > >
      > > > > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
      > > > > >
      > > > > > Hi Paul
      > > > > >
      > > > > > It looks like your output filter is rolling off a little bit
      > early.
      > > > > >
      > > > > > -Check the cores for L2 and L3. Should be 16 turns on yellow
      > cores.
      > > > > > -Check values for C24, 25, 26, should be 221, 471, 221 in that
      > order.
      > > > > > -On 20 meters put your RF probe on the primaries of both T4 and
      > T6. Readings should be comparable. If T6 is considerably less than T4
      > then your filter values are wrong or there is a bad solder joint in
      > there.
      > > > > >
      > > > > > Good luck!
      > > > > >
      > > > > > Warren Allgyer - W8TOD
      > > > > >
      > > > > >
      > > > > > --- In softrock40@yahoogroups.com, "pauldebono@" wrote:
      > > > > > >
      > > > > > > 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@" 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" 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
      View Source
      • 0 Attachment
        --- 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.
      Your message has been successfully submitted and would be delivered to recipients shortly.