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How much abuse can an RXTX take?

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  • warrenallgyer
    Secure in the knowledge I had a drawer full of replacements I decided to ask a pair of BS170 finals to take one for the team. I decided to do key-down,
    Message 1 of 3 , Nov 22, 2012
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      Secure in the knowledge I had a drawer full of replacements I decided to ask a pair of BS170 finals to take one for the team. I decided to do key-down, destructive testing to see how long they could run at full drive, full output before failing.

      My RXTX 30/20/17 puts out a whopping 3.3 watts at 13.8 VDC and full drive. I have always been very careful at this power level and backed it off considerably in actual operation. For this test I decided to run it at that power until it failed. I set up a spread sheet to log the total current drawn and the power output at 30 second intervals until the inevitable smoke began escaping front he KM5H case.

      At key down the rig produced 3.3 watts and total current drawn was 595 ma. After 2 minutes the power was down to 3.0 watts and current at 560 ma. At 8 minutes it was down to 2.8 watts out and 545 ma.

      So how long did the finals last. Well, after a full hour of key down they were still making 2.7 watts and drawing 525 ma. At that point I pardoned them with a hearty "well done!" and terminated the test.

      The KM5H case became noticeably warm at about 15 minutes. By 30 minutes it was very warm but it did not heat up more after that. I did not take the cover off at any point because I wanted to simulate real operating conditions so I don't know about the heat distribution inside.

      Bottom line, even at nearly 3 watts for a full hour the rig was making stable and very high power. No thermal runaway, no failure of any kind. Another tribute to a very solid, rugged design.

      Warren Allgyer - W8TOD
    • warrenallgyer
      I have received some welcome and constructive criticism of this post and my earlier one detailing the measurement of 3rd order distortion as a method of
      Message 2 of 3 , Nov 24, 2012
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        I have received some welcome and constructive criticism of this post and my earlier one detailing the measurement of 3rd order distortion as a method of determining safe power. For the record: The alignment and operating instructions contained in Robbie's notes, Alan's web page, and the cumulative knowledge of this board work and are accurate, complete, and all you need to get on the air effectively and safely.

        If you limit your CW and digital modes to 1 watt, and your SSB to 500 mw as has been suggested then you can pretty much be assured that your transmissions are clean. You need do nothing more and, in fact, you should do nothing more than this unless you are confident in your ability to "go it on your own". When you go beyond these parameters you risk damaging your transceiver and emitting illegal signals.

        I like to explore and, in the excitement of discovering something that is new to me, I like to share it. But my work has not had the peer review and the iterations that the official documentation has and should be considered "proceed at your own risk" at best.

        I hope I have not misled or offended.

        Regards,

        Warren Allgyer - W8TOD

        --- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@...> wrote:
        >
        > Secure in the knowledge I had a drawer full of replacements I decided to ask a pair of BS170 finals to take one for the team. I decided to do key-down, destructive testing to see how long they could run at full drive, full output before failing.
        >
        > My RXTX 30/20/17 puts out a whopping 3.3 watts at 13.8 VDC and full drive. I have always been very careful at this power level and backed it off considerably in actual operation. For this test I decided to run it at that power until it failed. I set up a spread sheet to log the total current drawn and the power output at 30 second intervals until the inevitable smoke began escaping front he KM5H case.
        >
        > At key down the rig produced 3.3 watts and total current drawn was 595 ma. After 2 minutes the power was down to 3.0 watts and current at 560 ma. At 8 minutes it was down to 2.8 watts out and 545 ma.
        >
        > So how long did the finals last. Well, after a full hour of key down they were still making 2.7 watts and drawing 525 ma. At that point I pardoned them with a hearty "well done!" and terminated the test.
        >
        > The KM5H case became noticeably warm at about 15 minutes. By 30 minutes it was very warm but it did not heat up more after that. I did not take the cover off at any point because I wanted to simulate real operating conditions so I don't know about the heat distribution inside.
        >
        > Bottom line, even at nearly 3 watts for a full hour the rig was making stable and very high power. No thermal runaway, no failure of any kind. Another tribute to a very solid, rugged design.
        >
        > Warren Allgyer - W8TOD
        >
      • Anthony Casorso
        Not misled and not offended, Glad to hear about your experiments. I didn t think that posts to a Yahoo group needed peer review. I don t see too many technical
        Message 3 of 3 , Nov 24, 2012
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          Not misled and not offended, Glad to hear about your experiments. I didn't think that posts to a Yahoo group needed peer review. I don't see too many technical papers citing Yahoo posts. I'm tempted to go even less PC but I don't want to deal with the flak. 

          Tony


          To: softrock40@yahoogroups.com
          From: allgyer@...
          Date: Sat, 24 Nov 2012 13:39:12 +0000
          Subject: [softrock40] Re: How much abuse can an RXTX take?

           
          I have received some welcome and constructive criticism of this post and my earlier one detailing the measurement of 3rd order distortion as a method of determining safe power. For the record: The alignment and operating instructions contained in Robbie's notes, Alan's web page, and the cumulative knowledge of this board work and are accurate, complete, and all you need to get on the air effectively and safely.

          If you limit your CW and digital modes to 1 watt, and your SSB to 500 mw as has been suggested then you can pretty much be assured that your transmissions are clean. You need do nothing more and, in fact, you should do nothing more than this unless you are confident in your ability to "go it on your own". When you go beyond these parameters you risk damaging your transceiver and emitting illegal signals.

          I like to explore and, in the excitement of discovering something that is new to me, I like to share it. But my work has not had the peer review and the iterations that the official documentation has and should be considered "proceed at your own risk" at best.

          I hope I have not misled or offended.

          Regards,

          Warren Allgyer - W8TOD

          --- In softrock40@yahoogroups.com, "warrenallgyer" <allgyer@...> wrote:
          >
          > Secure in the knowledge I had a drawer full of replacements I decided to ask a pair of BS170 finals to take one for the team. I decided to do key-down, destructive testing to see how long they could run at full drive, full output before failing.
          >
          > My RXTX 30/20/17 puts out a whopping 3.3 watts at 13.8 VDC and full drive. I have always been very careful at this power level and backed it off considerably in actual operation. For this test I decided to run it at that power until it failed. I set up a spread sheet to log the total current drawn and the power output at 30 second intervals until the inevitable smoke began escaping front he KM5H case.
          >
          > At key down the rig produced 3.3 watts and total current drawn was 595 ma. After 2 minutes the power was down to 3.0 watts and current at 560 ma. At 8 minutes it was down to 2.8 watts out and 545 ma.
          >
          > So how long did the finals last. Well, after a full hour of key down they were still making 2.7 watts and drawing 525 ma. At that point I pardoned them with a hearty "well done!" and terminated the test.
          >
          > The KM5H case became noticeably warm at about 15 minutes. By 30 minutes it was very warm but it did not heat up more after that. I did not take the cover off at any point because I wanted to simulate real operating conditions so I don't know about the heat distribution inside.
          >
          > Bottom line, even at nearly 3 watts for a full hour the rig was making stable and very high power. No thermal runaway, no failure of any kind. Another tribute to a very solid, rugged design.
          >
          > Warren Allgyer - W8TOD
          >


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