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71344Re: Anyone built the Ensemble RXTX for 40-30- & 20 meters ?

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  • Ed
    Jan 3, 2013
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      Hi All,

      I thought that you might like to have a preview of the preformance of the filter thats used as part of the Murphy QRO Mods.
      I have included the results of the SoftRock 40 30 20 Filter as defined in the WB5RVZ build of the Ensemble TXRX. I measured the inductance of the Toroids at a frequency of 14 Mhz prior to checking the SoftRock Filter. The test sample toroids for L2 and L3 were wound with 16 turns and measured 831.83nH and 834.01nH. These results are close to the specification values quoted within the build notes.

      Summary of Results:

      SoftRock 40 30 20 Filter:-

      Insertion Loss at 14 Mhz = 4.25dB
      Return Loss at 14 Mhz = 3.22dB ( SWR = 5.6 : 1 )
      2nd Harmonic Attenuation at 28 Mhz = 29dB
      3rd Harmonic Attenuation at 42 Mhz = 35dB
      Note: 1 W input results in 0.375 W output.

      Murphy QRO Mod Filter:-

      Insertion Loss at 14 Mhz = 0.33dB
      Return Loss at 14 Mhz = 21.3dB ( SWR = 1.19 : 1 )
      2nd Harmonic Attenuation at 28 Mhz = 25.78dB
      3rd Harmonic Attenuation at 42 Mhz = 49.1dB
      Note: 1 W input results in 0.926 W output



      The plots of these filters are shown in the Photos Section under GM3SBC

      General Note: Both filters included transformer T6 during the tests.




      Ed Murphy

      Profile:
      Senior Research Engineer
      Electronic Systems Consultant.
      Principal Engineer Airframe, Unmanned Air Vehicles.
      Principal Engineer Reliability, Fire Control Radar
      Pilot ( General Aviation and Sailplane )
      Radio Station GM3SBC
      Musician ( Jazz Flautist )
      Inventor.


      --- In softrock40@yahoogroups.com, "barry underwood" wrote:
      >
      > 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
      > > > > >
      > > > >
      > > >
      > >
      >
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