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Re: ATS3b Power Out

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  • radio_kx0r
    ... Steve, You ve really done a lot of serious work on your rig! Sounds like your method of optimizing is good, but you may have succeeded in getting to much
    Message 1 of 4 , Apr 30, 2008
      --- In AT_Sprint@yahoogroups.com, "Steven Pituch" <list2@...> wrote:


      You've really done a lot of serious work on your rig! Sounds like
      your method of optimizing is good, but you may have succeeded in
      getting to much power out of the rig! I think an ampere going in,
      after "matching", is too much.

      Your dummy load error is significant. You may be able to correct it
      close to 50 ohms with a parallel resistor. It would help a lot of
      you could check it with an antenna analyzer at RF.

      You RS meter may be fine. They key is to check it against
      a "standard", such as a multimeter that has been recently calibrated
      against real standards. If you can measure volts accurately, and you
      can get 1% resistors, then you can check and measure current; you
      also can find any error in your meter's current scale and correct it

      The WM-1 may not read accurately when connected to a non-50-ohm load.
      The cables will transform the non-50-ohm impedances into different
      complex values also.

      One warning is that once you get everything at 50 ohms, your ATS-3B
      may deliver even more power than now, so the current may go too high
      and the power out may be excessive. I hope not, but this might
      happen. You may have to go through one more round of tweaking, since
      the rig really needs to be set up for reasonable currents, good
      efficiency, and a 5.0 watt maximum into 50 ohms.

      I think you have more patience than I do.

      At least we're pretty sure you're a victim of measurement errors
      adding together.

      This is partly why corporations with many pieces of test equipment
      spend huge sums doing scheduled calibrations and getting
      certificates, even when the equipment seems to be just fine.

      Hang in there!



      > Hi Carey and All,
      > Thanks Carey for your thoughtful and detailed reply. It is exactly
      the kind
      > of wisdom I was looking for.
      > I think I purchased my multimeter after speaking with Wayne Burdick
      > building my Sierra. I did purchase it to check RF power. That
      would put it
      > at over 10-12 years old. It is a Radio Shack 22-168A. It always
      seemed to
      > be a nice tool. I hardly ever check current with it, mostly just
      > and voltage. I don't have anything else to compare it to. I think
      its time
      > to consider buying another one.
      > The dummy load in my MFJ 949 E is reading 56.7 Ohms. There's 13
      > right there! I can't back figure the math, but hoping this means
      that my
      > Watt meter is reading low. I suppose you recommend the Norcal
      Dummy load.
      > I was reading about the Accuprobe which is OP amp compensated, but
      > Norcal calibration chart seems adequate enough. I had had built
      two other
      > more accurate dummy loads years ago but discarded them after a few
      > because of the leaking mineral oil.
      > I would appreciate any advice on purchasing a decent multi meter.
      There are
      > so many out there now. Should I stay away from auto ranging? It
      there one
      > out there better than others under $100. Etc.
      > The way I adjusted the output filters:
      > I studied all the available documentation. I tried adjusting C3F
      as Mike
      > had suggested and C4F as you had in a few cases but found that only
      > C2F had a positive impact on the output power. I would first peak
      > module with the stock LF1 and LF2 number of turns by compressing or
      > expanding the turn spacing. If I got to a fully compressed or
      > toroid, if I thought that adding or subtracting a turn would help I
      > try that. Otherwise I would add about 20 uF to C2F and try again.
      > after doing this I would have to add or subtract turns to get to an
      > range. It seems that most of the time expanding turns on LF1
      initiated a
      > current trip, while expanding turns on LF2 would increase the
      power out
      > incrementally. I did this for hours at a time until I got the
      apparent 5 W
      > out. Of course some of the copper traces are gone at the toroids
      since I
      > replaced them about a dozen times for each module.
      > As I said earlier I was tripping the current limiter at about 4 W I
      > I got 5 W out on 40 m after doing your mod of R47, but it was on
      the hairy
      > edge when I hooked it up to an antenna. That's when I replaced R47
      with a
      > 470 Ohm resistor. It wouldnake sense that maybe I am actuaally
      putting out
      > 5.5 W or more and thus the high current.
      > I have the feeling that my power readings are one-half to one Watt
      too low.
      > 73 and thanks again,
      > Steve, W2MY
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