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Re: AW: [regenrx] Re: Cascode regen detector

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  • Udo Peters
    Hi Hue, thank you very much for the (late ;-) reply to my post from May. This positive effect of the balanced antenna was found by accident. I only tried this
    Message 1 of 20 , Aug 1 1:15 AM
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      Hi Hue,
      thank you very much for the (late ;-) reply to my post from May. This positive effect of the balanced antenna was found by accident. I only tried this on ten meters because of limited space. It would be very interesting to try this now on 40 meters (space permitting). But, I'm a little afraid that the detector could be overloaded by such a big antenna.
      There is one more interesting point about antenna connection: Many designers of Regens propose to couple the antenna to the input circuit inductively instead of using capacitive coupling to the top of the input circuit. I must admit that I didn't try this. I'm a little lazy when it comes to winding coils.
      I found an interesting article in QST Jan. 1939 written by the famous Fred Sutter (designer of the QSL 40 transmitter). He stated that the selectivity of a Regen could be improved, especially for CW reception, by using a very short antenna (he used a 12 inch whip) coupled directly to a tap of the input circuit. For his Regen in Hartley configuration he used the same tap where the cathode of the tube was connected.
      I tried this on my Regen with very good results. He also wrote in his article that a good ground connection was required. This is consistent with my own experience. I use a tube of my heating system. Since my shack is under the roof, this makes a fairly long connection to the earth. In my opinion, the antenna and the ground must be considered as a unit. So I think that the long ground connection also acts as an antenna.

      73 de Udo, dk3bi

      --- Hue Miller <kargo_cult@...> schrieb am So, 1.8.2010:

      Von: Hue Miller <kargo_cult@...>
      Betreff: Re: AW: [regenrx] Re: Cascode regen detector
      An: regenrx@yahoogroups.com
      Datum: Sonntag, 1. August, 2010 00:03 Uhr

      From: Udo Peters

      Sent: Friday, May 14, 2010 9:44 AM

      Subject: AW: [regenrx] Re: Cascode regen detector

      >Hi Hue and the group,

      you can see my version of such a cascode regen here:

      http://www.dk3bi.de/fileadmin/Images/Ham_Radio/Regen_RX/regen_sch.jpg

      I used a former version of this circuit in 1968 and it worked perfectly well on 10 meters. But only when I connected a symmetrical dipole as the antenna. With a random wire antenna and normal ground the hand capacity effects were extremely bad.

      73 de Udo, dk3bi

      Udo- thanks, VERY interesting point. The balanced antenna idea never would have occurred to me. Your point about the balanced antenna, this is the first time I have seen this in many years of reading about regens. It's a valuable addition to the regen receiver lore.
      -Hue K7HUE
    • Hue Miller
      Udo, yes I have seen this article also. I also recall an article in our Shortwave Craft magazine from the 1930s that showed a simple regen, as most common
      Message 2 of 20 , Aug 1 3:10 AM
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        Udo, yes I have seen this article also. I also recall an article in our "Shortwave Craft" magazine from the
        1930s that showed a simple regen, as most common then, of 2 or 3 tubes, that used a smallish loop
        antenna, roughly 12 x 10 inches, if I recall. ( so I say roughly, 30 x 25 cm ) as the ONLY tuned circuit
        AND the antenna. The article had no complaints about distance of reception, but of course this would
        be a terrible idea from the standpoint of stability. I also recall Michael Rainey's "Wheatstone Bridge
        Regenerative" which removed the tuned circuit practically from any antenna influences. ( Michael's
        circuit is the only modern instance of this circuit that I have seen, but the similar idea was used
        in US Army transmitter-receivers SCR-131 & 161 from mid 1930s, which used a 3 tube autodyne
        receiver coupled to a large loop ( diamond shaped, roughly 5 feet per side ). ) -Hue

        [Non-text portions of this message have been removed]
      • Hue Miller
        Here is an interesting quote I found: Something I noticed when fooling around is that at the lower detector voltage I was getting enough hand-capacitance on
        Message 3 of 20 , Aug 1 3:24 AM
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          Here is an interesting quote I found:

          "Something I noticed when fooling around is that at the lower detector
          voltage I was getting
          enough hand-capacitance on the regen cap to where I was ready to make a
          shield and look
          for a larger knob. Once I got up to 22 volts, though, the hand capacitance
          doesn't seem to be an issue."

          I have never heard about this as an issue ( =problem) with lower voltages
          before. Any comments?

          This quote is from page:

          http://www.sparkbench.com/homebrew/grebe/cr18.html

          For some reason I had an urge to look it up. I suppose the connection is
          that the Grebe CR-18's
          coils are right out there in the air. I have admired the CR-18 for many
          years now, ever since
          as a youngster reading a book "Great Expeditions of National Geographic"
          which had an article
          about exploring Mongolia, and showing our travelers letting some of the
          local people listen
          to their CR-18. This in the late 1920s. Probably this receiver is way out of
          my price range now.
          I did have a very historic Grebe CR-1 at one time; I traded it away, and
          most people say I was
          crazy to do that. -Hue
        • davidpnewkirk
          ... [deletions] ... Sutter s electrically very short antenna was a high impedance to begin with, and then he connected that high impedance to the cathode of
          Message 4 of 20 , Aug 7 9:05 PM
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            --- In regenrx@yahoogroups.com, Udo Peters <dk3bi@...> wrote:

            [deletions]

            > I found an interesting article in QST Jan. 1939 written by the
            > famous Fred Sutter (designer of the QSL 40 transmitter). He stated
            > that the selectivity of a Regen could be improved,
            > especially for CW reception, by using a very short antenna
            > (he used a 12 inch whip) coupled directly to a tap of the input
            > circuit. For his Regen in Hartley configuration he used the same
            > tap where the cathode of the tube was connected.

            Sutter's electrically very short antenna was a high impedance to begin with, and then he connected that high impedance to the cathode of his Hartley detector (a low-impedance point). What he achieved in through this mismatch was (a) very light loading of the tuned circuit and (b) great overall reduction in the strength of signals applied to the detector.

            That lightly loading a tuned circuit should improve its selectivity makes intuitive sense. What's less intuitive is that greater selectivity is achievable with a regenerative detector subjected to weak signals than the same detector subjected to strong(er) signals. To learn more about this, search this group for the word

            Robinson

            and sift through those messages (I think 16 hits are returned) until you find my postings of excerpts from H. A. Robinson's "Regenerative Detectors" article from 1933 *QST*.

            To get maximum selectivity from a regenerative detector across a wide range of incoming-signal strengths, some means should be made available to smoothly adjust, at will, how much signal is applied to the detector. An RF-input control that doesn't change the loading on the detector tuned circuit, and hence the pitch of received signals with the detector oscillating, is preferable. One simple approach to achieving this would be a low-gain tuned-input buffer amplifier lightly coupled to the detector, with a potentiometer connected between the antenna and the buffer tuned circuit.

            BTW, that using a balanced antenna (rather than a random wire) with an bufferless detector reduces body-capacitance effects makes sense when we realize that a balanced antenna provides both "signal" and "return" connections for signals applied to the detector, and to the signal generated/reradiated by the detector. With a single-wire antenna, the RF return is made through whatever other wires and conductors happen to be connected to the receiver. The impedance presented by those wires and conductors, which the presence of the conductive, 95%-water radio operator increasingly affects as frequency increases, therefore plays a greater role in detector loading than when a balanced antenna is used.

            Using a balanced antenna and/or RF buffer can also stop tunable hum. Tunable hum occurs when a radiating detector's input-RF return path passes through power-supply rectifier diodes, the switching action of which in effect modulates the loading applied to the detector and the amplitude of incoming and radiated signals. The more efficient, nonswitched RF return provided by a balanced antenna works to end-run such line-switch loading. (Bypassing power-supply rectifier diodes with ac-rated 0.01-uF ceramic capacitors [so the diodes can't act as switches at RF) can help as well. Bypassing each lead of the power-transformer's high-voltage secondary to chassis may also be necessary. An power transformer with an electrostatic shield between its primary and secondaries can help as well.)

            Putting an RF choke in the form of a ferrite ring or snap-on core or cable/wire turns around a ferrite rod in *every* interconnecting wire and cable you *don't* want to serve as an RF ground is another thing to try in solving the "reducing body capacitance and tunable hum puzzle." But IMO, shielding the detector and isolating it from the antenna with a buffer amplifier are steps 1 and 2.

            Best regards,

            Dave
            amateur radio W9VES
          • Larry Beaty
            Dave et all, Years ago, yeah, I m beyond boyhood! The National Semiconductor Company had an application note book on radio or such. I cannot remember the
            Message 5 of 20 , Aug 8 6:21 AM
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              Dave et all,



              Years ago, yeah, I'm beyond boyhood! The National Semiconductor Company had
              an application note book on radio or such. I cannot remember the name, but
              this must have been in the 70s. In that (blue) book was a dissertation on
              vertical wire (automobile antenna) vs. loopstick antenna. The dissertation
              was very complete with all the math to prove the author's point that the
              auto antenna gave more RF voltage to the radio than the loopstick did.



              An excellent article if only I could remember more about the book. I
              believe in the same book was a chapter on "Floobydust" - a name I am not
              liable to forget. National had some great application notes.



              Larry



              From: regenrx@yahoogroups.com [mailto:regenrx@yahoogroups.com] On Behalf Of
              davidpnewkirk
              Sent: Sunday, August 08, 2010 12:05 AM
              To: regenrx@yahoogroups.com
              Subject: [regenrx] Re: Cascode regen detector





              --- In regenrx@yahoogroups.com <mailto:regenrx%40yahoogroups.com> , Udo
              Peters <dk3bi@...> wrote:

              [deletions]

              > I found an interesting article in QST Jan. 1939 written by the
              > famous Fred Sutter (designer of the QSL 40 transmitter). He stated
              > that the selectivity of a Regen could be improved,
              > especially for CW reception, by using a very short antenna
              > (he used a 12 inch whip) coupled directly to a tap of the input
              > circuit. For his Regen in Hartley configuration he used the same
              > tap where the cathode of the tube was connected.

              Sutter's electrically very short antenna was a high impedance to begin with,
              and then he connected that high impedance to the cathode of his Hartley
              detector (a low-impedance point). What he achieved in through this mismatch
              was (a) very light loading of the tuned circuit and (b) great overall
              reduction in the strength of signals applied to the detector.

              That lightly loading a tuned circuit should improve its selectivity makes
              intuitive sense. What's less intuitive is that greater selectivity is
              achievable with a regenerative detector subjected to weak signals than the
              same detector subjected to strong(er) signals. To learn more about this,
              search this group for the word

              Robinson

              and sift through those messages (I think 16 hits are returned) until you
              find my postings of excerpts from H. A. Robinson's "Regenerative Detectors"
              article from 1933 *QST*.

              To get maximum selectivity from a regenerative detector across a wide range
              of incoming-signal strengths, some means should be made available to
              smoothly adjust, at will, how much signal is applied to the detector. An
              RF-input control that doesn't change the loading on the detector tuned
              circuit, and hence the pitch of received signals with the detector
              oscillating, is preferable. One simple approach to achieving this would be a
              low-gain tuned-input buffer amplifier lightly coupled to the detector, with
              a potentiometer connected between the antenna and the buffer tuned circuit.

              BTW, that using a balanced antenna (rather than a random wire) with an
              bufferless detector reduces body-capacitance effects makes sense when we
              realize that a balanced antenna provides both "signal" and "return"
              connections for signals applied to the detector, and to the signal
              generated/reradiated by the detector. With a single-wire antenna, the RF
              return is made through whatever other wires and conductors happen to be
              connected to the receiver. The impedance presented by those wires and
              conductors, which the presence of the conductive, 95%-water radio operator
              increasingly affects as frequency increases, therefore plays a greater role
              in detector loading than when a balanced antenna is used.

              Using a balanced antenna and/or RF buffer can also stop tunable hum. Tunable
              hum occurs when a radiating detector's input-RF return path passes through
              power-supply rectifier diodes, the switching action of which in effect
              modulates the loading applied to the detector and the amplitude of incoming
              and radiated signals. The more efficient, nonswitched RF return provided by
              a balanced antenna works to end-run such line-switch loading. (Bypassing
              power-supply rectifier diodes with ac-rated 0.01-uF ceramic capacitors [so
              the diodes can't act as switches at RF) can help as well. Bypassing each
              lead of the power-transformer's high-voltage secondary to chassis may also
              be necessary. An power transformer with an electrostatic shield between its
              primary and secondaries can help as well.)

              Putting an RF choke in the form of a ferrite ring or snap-on core or
              cable/wire turns around a ferrite rod in *every* interconnecting wire and
              cable you *don't* want to serve as an RF ground is another thing to try in
              solving the "reducing body capacitance and tunable hum puzzle." But IMO,
              shielding the detector and isolating it from the antenna with a buffer
              amplifier are steps 1 and 2.

              Best regards,

              Dave
              amateur radio W9VES





              [Non-text portions of this message have been removed]
            • Hue Miller
              From: Larry Beaty Dave et all, Years ago, yeah, I m beyond boyhood! The National Semiconductor Company had an application note book on radio or such. I cannot
              Message 6 of 20 , Aug 9 2:37 AM
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                From: Larry Beaty
                Dave et all,

                Years ago, yeah, I'm beyond boyhood! The National Semiconductor Company had
                an application note book on radio or such. I cannot remember the name, but
                this must have been in the 70s. In that (blue) book was a dissertation on
                vertical wire (automobile antenna) vs. loopstick antenna. The dissertation
                was very complete with all the math to prove the author's point that the
                auto antenna gave more RF voltage to the radio than the loopstick did.

                An excellent article if only I could remember more about the book. I
                believe in the same book was a chapter on "Floobydust" - a name I am not
                liable to forget. National had some great application notes.

                Larry


                -Larry, you sure that was Nat'l Semi book? That doesn't sound like their territory.
                Kind of reminds me of a large "applications" book put out by Mallory Company
                in the 1950s or 1960s. Also, as for FETs vs bipolars in the front end, you could
                look at Drake's SPR-1 or their 6-meter transceiver (can't remember model number )
                where FETs did a fine job. I see the front ends of the Radio Shack DX-150/160
                and Allied 2516 receivers also used FETs. I have a UHF receiver here waiting
                to be taken apart ( single channel AM aviation 225-300 MHz ) that has a bunch
                of nice 2N4416 FETs inside. -Hue Miller

                [Non-text portions of this message have been removed]
              • Udo Peters
                Hi David, thank you very much for the information. I will have a look at the Robinson article. 73 de Udo, dk3bi [Non-text portions of this message have been
                Message 7 of 20 , Aug 9 4:57 AM
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                  Hi David,
                  thank you very much for the information. I will have a look at the Robinson article.
                  73 de Udo, dk3bi













                  [Non-text portions of this message have been removed]
                • Larry Beaty
                  Hue, Absolutely sure it was National Semiconductor book. I may have a copy stored in another state. You do know National has stated they will stay in the
                  Message 8 of 20 , Aug 9 7:22 AM
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                    Hue,

                    Absolutely sure it was National Semiconductor book. I may have a copy
                    stored in another state. You do know National has stated they will stay in
                    the analog market rather than cover any digital products. So analog
                    reception is down their ally.



                    As I remember, the ap note does not appear on the National site. I may have
                    some contacts in National that I could query. New project for me to
                    persue.



                    I agree with you, many manufacturers used FETs. Was this to promote some
                    specmanship? Weren't the FETs pushed just a little too hard? John was sure
                    a FET would be a much better front end. After all, all these manufacturers
                    were using FETs in their front ends. He found the FETs overloaded on strong
                    signals where the bipolar had a wider range. I am just a messenger, John
                    did the work and I do trust John, very thorough engineer.



                    Larry



                    From: regenrx@yahoogroups.com [mailto:regenrx@yahoogroups.com] On Behalf Of
                    Hue Miller
                    Sent: Monday, August 09, 2010 5:37 AM
                    To: regenrx@yahoogroups.com
                    Subject: Re: [regenrx] Re: Cascode regen detector







                    From: Larry Beaty
                    Dave et all,

                    Years ago, yeah, I'm beyond boyhood! The National Semiconductor Company had
                    an application note book on radio or such. I cannot remember the name, but
                    this must have been in the 70s. In that (blue) book was a dissertation on
                    vertical wire (automobile antenna) vs. loopstick antenna. The dissertation
                    was very complete with all the math to prove the author's point that the
                    auto antenna gave more RF voltage to the radio than the loopstick did.

                    An excellent article if only I could remember more about the book. I
                    believe in the same book was a chapter on "Floobydust" - a name I am not
                    liable to forget. National had some great application notes.

                    Larry

                    -Larry, you sure that was Nat'l Semi book? That doesn't sound like their
                    territory.
                    Kind of reminds me of a large "applications" book put out by Mallory Company

                    in the 1950s or 1960s. Also, as for FETs vs bipolars in the front end, you
                    could
                    look at Drake's SPR-1 or their 6-meter transceiver (can't remember model
                    number )
                    where FETs did a fine job. I see the front ends of the Radio Shack
                    DX-150/160
                    and Allied 2516 receivers also used FETs. I have a UHF receiver here waiting
                    to be taken apart ( single channel AM aviation 225-300 MHz ) that has a
                    bunch
                    of nice 2N4416 FETs inside. -Hue Miller

                    [Non-text portions of this message have been removed]





                    [Non-text portions of this message have been removed]
                  • William
                    I remember the book, National had a lot of good ap-notes in their old analog manuals. If you go to Electronics Design Magazine( http://electronicdesign.com/
                    Message 9 of 20 , Aug 9 8:51 AM
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                      I remember the book, National had a lot of good ap-notes in their old analog manuals. If you go to Electronics Design Magazine( http://electronicdesign.com/ )and ask Robert A Pease one of the regular authors in the Commentary section at the bottom of the page for help obtaining the article he may beable to help. It was a sad day for National when they "out sourced" him.
                      Bill Higdon

                      --- In regenrx@yahoogroups.com, "Larry Beaty" <lbeaty3@...> wrote:
                      >
                      > Hue,
                      >
                      > Absolutely sure it was National Semiconductor book. I may have a copy
                      > stored in another state. You do know National has stated they will stay in
                      > the analog market rather than cover any digital products. So analog
                      > reception is down their ally.
                      >
                      >
                      >
                      > As I remember, the ap note does not appear on the National site. I may have
                      > some contacts in National that I could query. New project for me to
                      > persue.
                      >
                      >
                      >
                      > I agree with you, many manufacturers used FETs. Was this to promote some
                      > specmanship? Weren't the FETs pushed just a little too hard? John was sure
                      > a FET would be a much better front end. After all, all these manufacturers
                      > were using FETs in their front ends. He found the FETs overloaded on strong
                      > signals where the bipolar had a wider range. I am just a messenger, John
                      > did the work and I do trust John, very thorough engineer.
                      >
                      >
                      >
                      > Larry
                      >
                      >
                      >
                      > From: regenrx@yahoogroups.com [mailto:regenrx@yahoogroups.com] On Behalf Of
                      > Hue Miller
                      > Sent: Monday, August 09, 2010 5:37 AM
                      > To: regenrx@yahoogroups.com
                      > Subject: Re: [regenrx] Re: Cascode regen detector
                      >
                      >
                      >
                      >
                      >
                      >
                      >
                      > From: Larry Beaty
                      > Dave et all,
                      >
                      > Years ago, yeah, I'm beyond boyhood! The National Semiconductor Company had
                      > an application note book on radio or such. I cannot remember the name, but
                      > this must have been in the 70s. In that (blue) book was a dissertation on
                      > vertical wire (automobile antenna) vs. loopstick antenna. The dissertation
                      > was very complete with all the math to prove the author's point that the
                      > auto antenna gave more RF voltage to the radio than the loopstick did.
                      >
                      > An excellent article if only I could remember more about the book. I
                      > believe in the same book was a chapter on "Floobydust" - a name I am not
                      > liable to forget. National had some great application notes.
                      >
                      > Larry
                      >
                      > -Larry, you sure that was Nat'l Semi book? That doesn't sound like their
                      > territory.
                      > Kind of reminds me of a large "applications" book put out by Mallory Company
                      >
                      > in the 1950s or 1960s. Also, as for FETs vs bipolars in the front end, you
                      > could
                      > look at Drake's SPR-1 or their 6-meter transceiver (can't remember model
                      > number )
                      > where FETs did a fine job. I see the front ends of the Radio Shack
                      > DX-150/160
                      > and Allied 2516 receivers also used FETs. I have a UHF receiver here waiting
                      > to be taken apart ( single channel AM aviation 225-300 MHz ) that has a
                      > bunch
                      > of nice 2N4416 FETs inside. -Hue Miller
                      >
                      > [Non-text portions of this message have been removed]
                      >
                      >
                      >
                      >
                      >
                      > [Non-text portions of this message have been removed]
                      >
                    • afelino
                      Larry, You are referring to the 1980 National Semiconductor Audio/ Radio Handbook, a rare copy of which I have just dug out from the garage. The discussion you
                      Message 10 of 20 , Aug 9 7:41 PM
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                        Larry,

                        You are referring to the 1980 National Semiconductor Audio/
                        Radio Handbook, a rare copy of which I have just dug out from the garage. The discussion you mentioned is on pages 3-1 to 3-3. These books seemed to be hard to find a few years back, but with everyone having dumped their paper data books it might be easier now. The preface to the book says it tries to treat the second-order design issues in audio (and to a lesser extent radio) at an intuitive level suitable for those "between the hobbyist and the engineer." Some of the material is dated, referring to ancient chips, but it's still a good reference book with some nice surprises.

                        73, af wn6q

                        --- In regenrx@yahoogroups.com, "Larry Beaty" <lbeaty3@...> wrote:
                        >
                        > Dave et all,
                        >
                        >
                        >
                        > Years ago, yeah, I'm beyond boyhood! The National Semiconductor Company had
                        > an application note book on radio or such. I cannot remember the name, but
                        > this must have been in the 70s. In that (blue) book was a dissertation on
                        > vertical wire (automobile antenna) vs. loopstick antenna. The dissertation
                        > was very complete with all the math to prove the author's point that the
                        > auto antenna gave more RF voltage to the radio than the loopstick did.
                        >
                        >
                        >
                        > An excellent article if only I could remember more about the book. I
                        > believe in the same book was a chapter on "Floobydust" - a name I am not
                        > liable to forget. National had some great application notes.
                        >
                        >
                        >
                        > Larry
                        >
                        >
                      • davidpnewkirk
                        ... I ve got a copy of that as well; much good stuff generally, but especially--still applicable nowadays--details on the application of the LM380 and LM386
                        Message 11 of 20 , Aug 11 5:29 AM
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                          --- In regenrx@yahoogroups.com, "afelino" <wn6q@...> wrote:

                          > You are referring to the 1980 National Semiconductor Audio/
                          > Radio Handbook, a rare copy of which I have just dug out from
                          > the garage.

                          I've got a copy of that as well; much good stuff generally, but especially--still applicable nowadays--details on the application of the LM380 and LM386 audio amplifiers. Who knew that these parts and their relatives put out wideband noise that compels one to add output low-pass filtering and keep them separated as far as possible from the loopstick in AM-radio applications?

                          I also have a copy of the gigantic early-80s National linear databook that has fast and--no joke, it's in the part descriptor/page headline--"damn fast" operational amplifiers.

                          That was before National's databooks became Very Serious and all such stuff had to go. Maybe stuff like "floobydust" was allowed to hang on a bit longer at the published-shop-talk level.

                          But that reminds me: If you haven't read Bob Pease writing about just about anything, you're in for a treat at

                          http://www.national.com/rap/

                          In particular, if you've ever wondered why the voltage across a just-discharged-for-safety-by-short-circuiting capacitor mysteriously rises above zero after you've removed the short, see his writing on dielectric absorption--"soakage"--at

                          http://electronicdesign.com/article/analog-and-mixed-signal/what-s-all-this-soakage-stuff-anyhow-6096.aspx

                          and then there's Muntzing:

                          http://www.national.com/rap/Story/0,1562,17,00.html

                          which technique, in my opinion, was an application of Larsen E Rapp's breakthrough "Putting Diagnostic Prognostication to Work" from April 1941 *QST*.

                          Best best regardses,

                          Dave
                          amateur radio W9VES
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