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Re: Anyone built the Ensemble RXTX for 40-30- & 20 meters ?

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  • barry underwood
    Paul, I just found time to have closer look at my Ensemble. The original power measurements I made were with a Watson power / SWR meter at the low end of it s
    Message 1 of 98 , Jan 3, 2013
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      Paul,

      I just found time to have closer look at my Ensemble. The original power measurements I made were with a Watson power / SWR meter at the low end of it's range, so could be a little out. I double checked by measuring the voltage across a 50Ohm dummy load with an oscilloscope. The input was set to 2.4V P/P as per instructions, the input signal being generated by the M0KGK IQ software. The output was as follows:

      7.1Mhz 1.5 Watts
      10.1Mhz 1.7 watts
      14.1Mhz 0.8 Watts

      20 metres is about 3dB down on 40 metres. I am not totally convinced that this is all in the output LPF as the voltage on the base of the driver transistor Q6 also dropped from 2.0V P/P on 7.1Mhz to 1.6V P/P on 14.1Mhz.

      An air test on 20m yesterday brought back four reports from Italy, Bulgaria and Serbia on SSB, so I am quite pleased with the performance with less than a watt!

      Baz



      --- In softrock40@yahoogroups.com, "pauldebono@..." wrote:
      >
      > I believe that low RF output on 20 meters, with the Ensemble RXTX 40-30-20 meters version is inherited.
      >
      > I have checked with other fora and received private emails complaining of low to very low output on 20 meters.
      >
      > There is even a particular constructor who has actually ordered a ready made unit and has the same symptoms !!!!
      >
      > Whoever is claiming to have one watt or over on 20 meters is just pushing hard the driver and/or the PA stage ,to well over their limits to make good for the roll off at 12 Mhz of the low pass filter.
      >
      > Yes, in plain language, the frequency response of the LPF, starts falling at around 12Mhz, causing a drop of half a watt or even less at the output socket, on 20 meters. Measurements were made by a practical RF probe, and frequencies confirmed, no fancy theoretical simulations !! At the secondary of T4,there is one watt or even more,if pushed harder, but it deteriorates slowly because of the low pass filter.
      >
      > Paul
      >
      > --- In softrock40@yahoogroups.com, "barry underwood" wrote:
      > >
      > >
      > >
      > >
      > > Paul,
      > >
      > > I have sorted mine now. The symptoms were exactly the same as yours - I was seeing 20Vp/p at the input to the LPF, but it was rolling off to nothing above 12Mhz at the ouptput. I checked all of the LPF filter calculations and they are spot on, so no need to mess with it. My problem was T4. All DC conditions were perfect, so it was the last thing to suspect. Out of desperation, I wound a new one. I am now getting 2 watts out on 40 and 1.5 watts on 20. One other symptom I had was instability when connected into anything other than a perfect 50 ohm load. The only clue pointing towards T4 was that putting an oscilloscope on the output pins of the two PA FETs showed that one was working much harder than the other. I am not sure what was wrong with T4, but I have had issues where the enamel has not fully stripped off the wire and a poor joint has resulted, even though it looked perfect.
      > >
      > > Baz
      > >
      > >
      > > --- In softrock40@yahoogroups.com, "pauldebono@" wrote:
      > > >
      > > > Baz,
      > > >
      > > > I have just seen your reply to to me message.
      > > >
      > > > I have just posted a reply about my findings.
      > > >
      > > > From what you say, we may have to modify the LPF !
      > > >
      > > > Paul
      > > >
      > > > --- In softrock40@yahoogroups.com, "barry underwood" wrote:
      > > > >
      > > > >
      > > > >
      > > > > I have just finished my Ensemble TX/RX for 40, 30, 20 and have the same problem. The output is just over a watt on 7Mhz, but rolls off to 0.5Watt at 10Mhz and 100 milliwatts on 14Mhz.
      > > > >
      > > > > Another problem I am having is instability when I connect a real antenna. All is well on a dummy load, but as soon as I connect my G5RV (Via an ATU) I get an oscillation around 11Mhz. has anyone seen this?
      > > > >
      > > > > I have checked and double checked the build, but can't find any obvious suspects.
      > > > >
      > > > > Baz, G4BUD
      > > > >
      > > >
      > >
      >
    • R. R. (Robby) Robson
      Gentlemen: Please review the projects on the new WB5RVZ website. I have added a Revisions/Errata tab to the menu on each project. Not much populated there,
      Message 98 of 98 , Jan 7, 2013
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        Gentlemen:

        Please review the projects on the new WB5RVZ website.
        I have added a "Revisions/Errata" tab to the menu on each project.  Not much populated there, but the RXTX info that was raised in this thread has been posted.

        Check it out.

        On Sun, Jan 6, 2013 at 9:43 AM, richard.lawn@... <rjlawn@...> wrote:
         

        I couldn't agree more about the need to make a clear errata page obvious and available on the website with dates. Tnx for making this suggestion.
        Rick
        W2JAZ



        --- In softrock40@yahoogroups.com, "hladikz" wrote:
        >
        > Hi Oms,
        >
        > I just ended RXTXE building and found those build changes for 40/30/20 version.
        >
        > I think that it will be very nice if you will add errata/changes subpage to your new documentation web. Date of changes will be also very usable. At this time if I am coreect there are two changes:
        >
        > 1. Crossing of ant TR leads
        > 2. changes of values for 40/30/20 LPF C's and L's (please add also previous number of winds for L, to allow avoid recounting of winds)
        >
        > Yet something missing?
        >
        > I also think that way of band variant selection is not very clear. Especially for beginners it is not simple to recognize that you must go to band subpage. It will be more friendly if there will be possibility to change bands variant on each page.
        >
        > On other way I think that Softrock DOC at all is excelent and very easy to understand.
        >
        > 73 Zdenek OK7DR
        >
        >
        >
        > --- In softrock40@yahoogroups.com, "R. R. (Robby) Robson" wrote:
        > >
        > > I have made the changes to the documentation. See
        > > http://wb5rvz.org/ensemble_rxtx/05_rf (be sure to select the 40/30/20m band
        > > option).
        > >
        > > On Thu, Jan 3, 2013 at 10:33 AM, pauldebono@
        > > wrote:
        > >
        > > > **
        > > >
        > > >
        > > > Tony,
        > > >
        > > > Thanks very much.
        > > >
        > > > I was the the one who raised the issue.
        > > > I had already started reducing the turns and was going to make the
        > > > capacitors variable to determine the optimum values.
        > > >
        > > > 73's
        > > >
        > > > Paul
        > > > 9H1FQ
        > > >
        > > >
        > > > --- In softrock40@yahoogroups.com, "Parks, Tony" wrote:
        > > > >
        > > > > Good Morning All,
        > > > >
        > > > > Sure looks like it would be appropriate to make the 40m/30m/20m LP filter
        > > > > component changes starting right away.
        > > > >
        > > > > I will get the schematic values changed today with the following changes:
        > > > >
        > > > > C24 and C26 each become 180pF
        > > > > C25 becomes 390pF
        > > > > L2 and L3 each become 0.6uH, 14 turns of #26 wire on T37-6 cores.
        > > > >
        > > > > A continue to appreciate the thoughtful input from the group and hope the
        > > > > kits are still providing a positive entry level SDR experience for many.
        > > > >
        > > > > Thanks and 73,
        > > > > Tony KB9YIG
        > > > >
        > > > > On Thu, Jan 3, 2013 at 8:15 AM, John Greusel wrote:
        > > > >
        > > > > > **
        > > >
        > > > > >
        > > > > >
        > > > > > My vote is that Tony's suggested change and Warren's empirical results
        > > > > > point strongly to this modest change as a good thing.
        > > > > > The prior variance in output for different builders makes me think it's
        > > > > > related to the bias differences (via Q6) that Warren uncovered
        > > > recently. In
        > > > > > other words, those of us that are experiencing near 1 watt output are
        > > > > > actually having much higher output with attenuation.
        > > > > >
        > > > > > John
        > > > > > KC9OJV
        > > > > >
        > > > > >
        > > > > > ------------------------------
        > > > > > *From:* warrenallgyer
        > > > > > *To:* softrock40@yahoogroups.com
        > > > > > *Sent:* Thursday, January 3, 2013 5:31 AM
        > > > > >
        > > > > > *Subject:* [softrock40] Re: Anyone built the Ensemble RXTX for 40-30- &
        > > >
        > > > > > 20 meters ?
        > > > > >
        > > > > >
        > > > > > I have bread-boarded and tested Tony's suggested filter with caps of
        > > > > > 180,390,180 pF and T37 toroids with 14 turns, again terminated in 47
        > > > ohms
        > > > > > and fed directly by the output of an MFJ antenna analyzer.
        > > > > >
        > > > > > 7 MHz: Reference at 0 dB
        > > > > > 10 MHz: -0.1 dB
        > > > > > 14.2 MHz: -.7 dB
        > > > > > 16.3 MHz: -3.0 dB
        > > > > > 20 MHz: -12.3 dB
        > > > > > 21 MHz: -15.2 dB
        > > > > >
        > > > > > Warren Allgyer - W8TOD
        > > > > >
        > > > > > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
        > > > > > >
        > > > > > > I just calculated different results with the external filter. The
        > > > > > > results reported previously were a comparison of simultaneous
        > > > readings
        > > > > > > on the input and the terminated output of the filter.
        > > > > > > The new readings are looking at the terminated output only and using
        > > > the
        > > > > > > value at 7MHz as the reference. Doing it this way I get
        > > > > > > 7 MHz: 0 dB10 MHz: -0.1 dB13.5 MHz: -3.3 dB14.0 MHz: -4.8 dB14.2 MHz:
        > > > > > > -5.4 dB 14.5 MHz: -6.6 dB
        > > > > > > The output of the analyzer, when terminated and measured separately
        > > > > > > across the range 7 - 14.5 MHz is flat within 0.2 dB.
        > > > > > > The discrepancy between the early results with simultaneous input and
        > > > > > > output measurements is the input impedance of the filter changes as
        > > > the
        > > > > > > filter begins to engage and that causes the voltage to rise. These
        > > > > > > latter results are more appropriate and still show a significant
        > > > problem
        > > > > > > with the specified turns counts and cap values
        > > > > > > I will build Tony's suggested filter and model it the same way.
        > > > > > >
        > > > > > >
        > > > > > > Warren Allgyer - W8TOD
        > > > > > >
        > > > > > > --- In softrock40@yahoogroups.com, "Parks, Tony" wrote:
        > > > > > > >
        > > > > > > > 16 turns on a T37-6 core is supposed to result in an 0.8uH inductor
        > > > > > > > according to the calculator on Diz's website.
        > > > > > > http://toroids.info/T37-6.php
        > > > > > > >
        > > > > > > > Checking the 40m/30m/20m LP filter design with AADE Filter Design
        > > > v4.5
        > > > > > > I
        > > > > > > > see about 1dB of additional attenuation at 14.3 MHz compared to
        > > > lower
        > > > > > > > frequencies.
        > > > > > > >
        > > > > > > > My recent experience with a freshly built 40m/30m/20m RXTX board
        > > > was
        > > > > > > the
        > > > > > > > 20m output was down about 1.5 dB.
        > > > > > > >
        > > > > > > > The capacitors supplied in the RXTX kit are 5%. Increasing
        > > > capacitor
        > > > > > > and
        > > > > > > > inductor values by 5% results in 2.5 dB 20m attenuation. Increasing
        > > > > > > > capacitor values by 5% and inductor values by 10% results in about
        > > > > > > 3.2 dB
        > > > > > > > of additional attenuation.
        > > > > > > >
        > > > > > > > The design seems to be reasonable but some kit builder's experience
        > > > > > > > suggests that the filter should be changed. Changing the 220pF
        > > > > > > capacitors
        > > > > > > > to 180pF, the 470pF capacitor to 390pF and the inductors to 0.6uH,
        > > > (14
        > > > > > > > turns on a T37-6 core), results in a LP filter with about the same
        > > > Z
        > > > > > > but
        > > > > > > > the 1dB of additional attenuation is at 18 MHz.
        > > > > > > >
        > > > > > > > Thoughts?
        > > > > > > >
        > > > > > > > Tony KB9YIG
        > > > > > > >
        > > > > > > > On Thu, Jan 3, 2013 at 4:14 AM, Orin wrote:
        > > > > > > >
        > > > > > > > > **
        > > > > > > > >
        > > > > > > > >
        > > > > > > > > --- In softrock40@yahoogroups.com, "warrenallgyer" wrote:
        > > > > > > > > >
        > > > > > > > > > Further to the above post:
        > > > > > > > > >
        > > > > > > > > > I have breadboarded the 43/30/20 filter externally, feeding it
        > > > > > > from an
        > > > > > > > > MFJ
        > > > > > > > > > antenna analyzer and terminating it on the breadboard with a 47
        > > > > > > ohm
        > > > > > > > > resister. I
        > > > > > > > > > have dual scope probes on for simultaneous measurement on the
        > > > > > > input and
        > > > > > > > > output
        > > > > > > > > > of the filter.
        > > > > > > > >
        > > > > > > > > Will you antenna analyzer measure inductance @ 14MHz? If so, what
        > > > > > > does it
        > > > > > > > > measure your inductors at. My 259B will give a result +/- 10nH
        > > > or so
        > > > > > > which
        > > > > > > > > is close enough for these filters.
        > > > > > > > >
        > > > > > > > >
        > > > > > > > > >
        > > > > > > > > > The 6 dB point of my breadboard filter is 12.5 MHz. At 14.2 MHz
        > > > > > > the
        > > > > > > > > output is 13
        > > > > > > > > > dB down.
        > > > > > > > > >
        > > > > > > > > > Toroids are T37 Yellow each 16 turns. Caps are 220 pf input and
        > > > > > > output
        > > > > > > > > shunts
        > > > > > > > > > with 470 pf. in the center shunt.
        > > > > > > > >
        > > > > > > > > I put those values into Elsie (800nH for the inductors) and got
        > > > > > > -1.3dB at
        > > > > > > > > 14.2MHz assuming 50 ohms input and your 47 ohms ouput. I tried
        > > > > > > adding 10%
        > > > > > > > > to the inductors (880nH) and got -2.6dB at 14.2MHz. 16 turns on a
        > > > > > > T37-6
        > > > > > > > > should give 768nH though and Elsie give -1dB at 14MHz in that
        > > > case.
        > > > > > > > >
        > > > > > > > > Another thing to try would be 14 turns on an T37-2 if you have
        > > > any
        > > > > > > around
        > > > > > > > > (I do from unused options on my Ensemble). The -2s have been more
        > > > > > > reliable
        > > > > > > > > for me in getting the 'advertised' inductance.
        > > > > > > > >
        > > > > > > > > Anyone wondering what "Elsie" is, it's an LC filter
        > > > design/network
        > > > > > > > > analysis program. I'm using the free student/hobbyist version.
        > > > > > > Details are
        > > > > > > > > here: http://tonnesoftware.com/elsie.html . I wish I could
        > > > justify
        > > > > > > > > spending the money for the full version.
        > > > > > > > >
        > > > > > > > > Orin.
        > > > > > > > >
        > > > > > > > >
        > > > > > > > >
        > > > > > > >
        > > > > > >
        > > > > >
        > > > > >
        > > > > >
        > > > > >
        > > > > >
        > > > >
        > > >
        > > >
        > > >
        > >
        > >
        > >
        > > --
        > > Cheers,
        > > Robby
        > >
        > > Richard R. (Robby) Robson
        > > LTC USA (RET)
        > > www.wb5rvz.com
        > > www.wb5rvz.org
        > > www.rafino.org
        > >
        >




        --
        Cheers,
        Robby
         
        Richard R. (Robby) Robson
        LTC USA (RET)
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