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Reducing VT Audio Hum

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  • Paul Christensen
    I am looking to reducing power supply hum in an audio stage. Presently, the chassis is used for the common filament return and accordingly, the chassis
    Message 1 of 18 , May 3, 2011
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      I am looking to reducing power supply hum in an audio stage. Presently,
      the chassis is used for the common filament return and accordingly, the
      chassis contains much 120 Hz current. From what I can measure, hum is being
      induced from the filament to the grid and cathode of a 6AQ5 and 12AU7 AF
      pre-driver.

      I am thinking of elevating the return filament from these two tubes and
      running the return with an insulated wire direct from the transformer.
      While 120 Hz current is still on the chassis, I may be able to reduce the
      effects of hum coupling. Another thought includes the use of 100-ohm
      potentiometer with a grounded tap to the chassis for use as a so-called "hum
      balance" control.

      Anyone care to share their experiences with getting rid of filament-induced
      power supply hum? Many Tnx!

      Paul, W9AC
    • kyoritsu
      Hi Paul, By floating the heaters, twisting the leads, and using a hum balancing pot, I ve succeeded in essentially eliminating all hum. Something else to
      Message 2 of 18 , May 3, 2011
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        Hi Paul,

        By floating the heaters, twisting the leads, and using a hum balancing pot, I've succeeded in essentially eliminating all hum. Something else to consider is the physical orientation of the audio output trans vis-a-vis the PS trans: sometimes turning the audio trans 90 deg can make an enormous difference.

        There's a good tutorial on this here:

        http://www.freewebs.com/valvewizard/index.html


        In particular, take a look at 'Heater Supply' notes and 'Grounding and Ground Schemes'.

        Rob




        --- In regenrx@yahoogroups.com, "Paul Christensen" <w9ac@...> wrote:
        >
        > I am looking to reducing power supply hum in an audio stage. Presently,
        > the chassis is used for the common filament return and accordingly, the
        > chassis contains much 120 Hz current. From what I can measure, hum is being
        > induced from the filament to the grid and cathode of a 6AQ5 and 12AU7 AF
        > pre-driver.
        >
        > I am thinking of elevating the return filament from these two tubes and
        > running the return with an insulated wire direct from the transformer.
        > While 120 Hz current is still on the chassis, I may be able to reduce the
        > effects of hum coupling. Another thought includes the use of 100-ohm
        > potentiometer with a grounded tap to the chassis for use as a so-called "hum
        > balance" control.
        >
        > Anyone care to share their experiences with getting rid of filament-induced
        > power supply hum? Many Tnx!
        >
        > Paul, W9AC
        >
      • ve7sl@shaw.ca
        Paul - I finally gave up trying to eliminate the hum in my Paraset s regen rcvr and built a small 6VDC filament supply using an LM17 fed from the filament
        Message 3 of 18 , May 3, 2011
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          Paul - I finally gave up trying to eliminate the hum in my Paraset's regen
          rcvr and built a small 6VDC filament supply using an LM17 fed from the
          filament windings (5v/6v) on the rx's power transformer. It totally
          eliminated 100% of the hum.

          Steve

          WEB - "The VE7SL Radio Notebook": http://members.shaw.ca/ve7sl
        • Prof. Arnaldo Coro Antich
          The risky use of PARASETS in the field during the II World War required to have a 6 volts battery to power the filaments, and a vibrator power supply for the
          Message 4 of 18 , May 3, 2011
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            The risky use of PARASETS in the field during the II World War required to
            have a 6 volts battery to power the filaments, and a vibrator power supply
            for the high voltage !
            Using the PARASETS from the typical European 220 volts or 240 volts AC
            power lines was very risky, because the German RDF teams could cut the
            power to the area and locate the place from where the PARASET was used !!!
            By the way, the very poor receiver bandspread should had made using it
            counting
            with an operator that had a safe crackers experts hands !!!
            In actual practice, according to radio historian Pat Hawker G3VA,
            Parasets were used
            receiving on a frequency far away removed from the transmit frequencies
            they used !!!
            73 and DX
            Arnie Coro
            CO2KK
            Regenerative receivers fan since 1954 !!!

            On 05/03/11 18:45, ve7sl@... wrote:
            > Paul - I finally gave up trying to eliminate the hum in my Paraset's regen
            > rcvr and built a small 6VDC filament supply using an LM17 fed from the
            > filament windings (5v/6v) on the rx's power transformer. It totally
            > eliminated 100% of the hum.
            >
            > Steve
            >
            > WEB - "The VE7SL Radio Notebook": http://members.shaw.ca/ve7sl
            >
            >
            >
            > ------------------------------------
            >
            > "In the interest of Regenerating radio's lost art of Regeneration"Yahoo! Groups Links
            >
            >
            >
            >
            >
          • Bill M
            I disagree with some of what Arnie says. I ll leave it at that. -Bill
            Message 5 of 18 , May 3, 2011
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              I disagree with some of what Arnie says.

              I'll leave it at that.

              -Bill



              Prof. Arnaldo Coro Antich wrote:
              > The risky use of PARASETS in the field during the II World War required to
              > have a 6 volts battery to power the filaments, and a vibrator power supply
              > for the high voltage !
              > Using the PARASETS from the typical European 220 volts or 240 volts AC
              > power lines was very risky, because the German RDF teams could cut the
              > power to the area and locate the place from where the PARASET was used !!!
              > By the way, the very poor receiver bandspread should had made using it
              > counting
              > with an operator that had a safe crackers experts hands !!!
              > In actual practice, according to radio historian Pat Hawker G3VA,
              > Parasets were used
              > receiving on a frequency far away removed from the transmit frequencies
              > they used !!!
              > 73 and DX
              > Arnie Coro
              > CO2KK
              > Regenerative receivers fan since 1954 !!!
              >
              > On 05/03/11 18:45, ve7sl@... wrote:
              >> Paul - I finally gave up trying to eliminate the hum in my Paraset's regen
              >> rcvr and built a small 6VDC filament supply using an LM17 fed from the
              >> filament windings (5v/6v) on the rx's power transformer. It totally
              >> eliminated 100% of the hum.
              >>
              >> Steve
              >>
              >> WEB - "The VE7SL Radio Notebook": http://members.shaw.ca/ve7sl
              >>
              >>
              >>
              >> ------------------------------------
              >>
              >> "In the interest of Regenerating radio's lost art of Regeneration"Yahoo! Groups Links
              >>
              >>
              >>
              >>
              >>
              >
              >
              >
              > ------------------------------------
              >
              > "In the interest of Regenerating radio's lost art of Regeneration"Yahoo! Groups Links
              >
              >
              >
              >
            • davidpnewkirk
              ... If the hum comes from ac tube heating, the answer is dc heater power. Sure, if you re both skilled and lucky, you may be able to float your heaters and
              Message 6 of 18 , May 3, 2011
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                --- In regenrx@yahoogroups.com, "Paul Christensen" <w9ac@...> wrote:

                > I am looking to reducing power supply hum in an audio stage.

                If the hum comes from ac tube heating, the answer is dc heater power.

                Sure, if you're both skilled and lucky, you may be able to float your heaters and dc-bias them such that hum is acceptable low. Or no matter how hard you try you may not be able to for reasons of ground looping and/or induction built into your layout. Dc heater feed end-runs all such problems not caused by induction from mains wiring and/or nearby transformers.

                For those of a purist bent, do consider the *why* of 6.3 and 12.6 tube-heater voltages: That was done to match the nominal battery voltage of automotive systems for tube use in car radios (cars used 6.3-V batteries before 12.6 V became standard). So dc-heating such tubes is actually more ideologically pure than using ac. :-)

                If the hum comes from inadequate plate/screen-supply filtering, you know what to do. Capacitors of hundreds of microfarads are cheap.

                Best regards,

                Dave
                amateur radio W9VES
              • Hue Miller
                I concur that this species of radio was mystifyingly user not-friendly. Manual antenna switching, sometimes NO antenna switching provided; very poor tuning
                Message 7 of 18 , May 3, 2011
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                  I concur that this species of radio was mystifyingly user not-friendly.
                  Manual antenna switching, sometimes NO antenna switching provided; very poor tuning bandspread;
                  no transmit sidetone.
                  I am very interested in the Pacific war anti-Japan resistance radios. It seems to me that unaccountably
                  the Allies were never by the end of the war able to develop a really satisfactory clandestine radio,
                  when you consider transmitter power and frequency range, power required, and weight. I really
                  can’t understand this. They certainly tried. One mistake, I think, was to use 6 volt tubes for the
                  receiver, when 1.5 volt tubes would require much less power; also a 4 tube regen would have
                  worked satisfactorily instead of providing a 5 or more tube superhet. And a single tube transmitter
                  would have done fine for the power required, which was never more than about 50W out, for stations
                  genuinely operating behind enemy lines. The Australian coastwatcher set 3BZ ran only 12W out.

                  My friend John saw a clandestine-type radio once for sale in the consignment area of Amateur
                  Radio Sales store in Seattle in the 1970s. There was a sign with it, “ $35 Makes a good Novice
                  set”. He says it came with something that looked like a vintage home electric fan, but was really
                  a motor-generator to generate HV DC for the transmitter.
                  -Hue M

                  From: Bill M
                  Sent: Tuesday, May 03, 2011 7:20 PM
                  To: regenrx@yahoogroups.com
                  Subject: Re: [regenrx] Re: Reducing VT Audio Hum REAL PARASETS USED 6 VOLTS ACCUMULATORS !!!


                  I disagree with some of what Arnie says.

                  I'll leave it at that.

                  -Bill

                  Prof. Arnaldo Coro Antich wrote:
                  > The risky use of PARASETS in the field during the II World War required to
                  > have a 6 volts battery to power the filaments, and a vibrator power supply
                  > for the high voltage !
                  > Using the PARASETS from the typical European 220 volts or 240 volts AC
                  > power lines was very risky, because the German RDF teams could cut the
                  > power to the area and locate the place from where the PARASET was used !!!
                  > By the way, the very poor receiver bandspread should had made using it
                  > counting
                  > with an operator that had a safe crackers experts hands !!!
                  > In actual practice, according to radio historian Pat Hawker G3VA,
                  > Parasets were used
                  > receiving on a frequency far away removed from the transmit frequencies
                  > they used !!!
                  > 73 and DX
                  > Arnie Coro
                  > CO2KK
                  > Regenerative receivers fan since 1954 !!!
                  >
                  > On 05/03/11 18:45, mailto:ve7sl%40shaw.ca wrote:
                  >> Paul - I finally gave up trying to eliminate the hum in my Paraset's regen
                  >> rcvr and built a small 6VDC filament supply using an LM17 fed from the
                  >> filament windings (5v/6v) on the rx's power transformer. It totally
                  >> eliminated 100% of the hum.
                  >>
                  >> Steve
                  >>
                  >> WEB - "The VE7SL Radio Notebook": http://members.shaw.ca/ve7sl
                  >>
                  >>
                  >>
                  >> ------------------------------------
                  >>
                  >> "In the interest of Regenerating radio's lost art of Regeneration"Yahoo! Groups Links
                  >>
                  >>
                  >>
                  >>
                  >>
                  >
                  >
                  >
                  > ------------------------------------
                  >
                  > "In the interest of Regenerating radio's lost art of Regeneration"Yahoo! Groups Links
                  >
                  >
                  >
                  >






                  [Non-text portions of this message have been removed]
                • Leonard Meek
                  Hue, I notice that a lot of emergency radios had indirect heated cathodes, like the Gibson Girl. Could it be that filament tubes were too fragile? A good
                  Message 8 of 18 , May 4, 2011
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                    Hue, I notice that a lot of "emergency" radios had indirect heated cathodes,
                    like the Gibson Girl. Could it be that filament tubes were too fragile? A
                    good bump could break the filament wire. However, I have a bunch of
                    proximity fuze tubes and they're all filament types. But their orientation
                    in the fuze and the fact that they weren't energized until the projectile
                    was out the muzzle and armed probably prevented the filaments from breaking.

                    Leonard

                    ----- Original Message -----
                    From: "Hue Miller" <kargo_cult@...>
                    To: <regenrx@yahoogroups.com>
                    Sent: Tuesday, May 03, 2011 8:19 PM
                    Subject: Re: [regenrx] Re: Reducing VT Audio Hum REAL PARASETS USED 6 VOLTS
                    ACCUMULATORS !!!


                    I concur that this species of radio was mystifyingly user not-friendly.
                    Manual antenna switching, sometimes NO antenna switching provided; very poor
                    tuning bandspread;
                    no transmit sidetone.
                    I am very interested in the Pacific war anti-Japan resistance radios. It
                    seems to me that unaccountably
                    the Allies were never by the end of the war able to develop a really
                    satisfactory clandestine radio,
                    when you consider transmitter power and frequency range, power required, and
                    weight. I really
                    can’t understand this. They certainly tried. One mistake, I think, was to
                    use 6 volt tubes for the
                    receiver, when 1.5 volt tubes would require much less power; also a 4 tube
                    regen would have
                    worked satisfactorily instead of providing a 5 or more tube superhet. And a
                    single tube transmitter
                    would have done fine for the power required, which was never more than about
                    50W out, for stations
                    genuinely operating behind enemy lines. The Australian coastwatcher set 3BZ
                    ran only 12W out.

                    My friend John saw a clandestine-type radio once for sale in the consignment
                    area of Amateur
                    Radio Sales store in Seattle in the 1970s. There was a sign with it, “ $35
                    Makes a good Novice
                    set”. He says it came with something that looked like a vintage home
                    electric fan, but was really
                    a motor-generator to generate HV DC for the transmitter.
                    -Hue M

                    From: Bill M
                    Sent: Tuesday, May 03, 2011 7:20 PM
                    To: regenrx@yahoogroups.com
                    Subject: Re: [regenrx] Re: Reducing VT Audio Hum REAL PARASETS USED 6 VOLTS
                    ACCUMULATORS !!!


                    I disagree with some of what Arnie says.

                    I'll leave it at that.

                    -Bill

                    Prof. Arnaldo Coro Antich wrote:
                    > The risky use of PARASETS in the field during the II World War required to
                    > have a 6 volts battery to power the filaments, and a vibrator power supply
                    > for the high voltage !
                    > Using the PARASETS from the typical European 220 volts or 240 volts AC
                    > power lines was very risky, because the German RDF teams could cut the
                    > power to the area and locate the place from where the PARASET was used !!!
                    > By the way, the very poor receiver bandspread should had made using it
                    > counting
                    > with an operator that had a safe crackers experts hands !!!
                    > In actual practice, according to radio historian Pat Hawker G3VA,
                    > Parasets were used
                    > receiving on a frequency far away removed from the transmit frequencies
                    > they used !!!
                    > 73 and DX
                    > Arnie Coro
                    > CO2KK
                    > Regenerative receivers fan since 1954 !!!
                    >
                    > On 05/03/11 18:45, mailto:ve7sl%40shaw.ca wrote:
                    >> Paul - I finally gave up trying to eliminate the hum in my Paraset's
                    >> regen
                    >> rcvr and built a small 6VDC filament supply using an LM17 fed from the
                    >> filament windings (5v/6v) on the rx's power transformer. It totally
                    >> eliminated 100% of the hum.
                    >>
                    >> Steve
                    >>
                    >> WEB - "The VE7SL Radio Notebook": http://members.shaw.ca/ve7sl
                    >>
                    >>
                    >>
                    >> ------------------------------------
                    >>
                    >> "In the interest of Regenerating radio's lost art of Regeneration"Yahoo!
                    >> Groups Links
                    >>
                    >>
                    >>
                    >>
                    >>
                    >
                    >
                    >
                    > ------------------------------------
                    >
                    > "In the interest of Regenerating radio's lost art of Regeneration"Yahoo!
                    > Groups Links
                    >
                    >
                    >
                    >






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



                    ------------------------------------

                    "In the interest of Regenerating radio's lost art of Regeneration"Yahoo!
                    Groups Links
                  • Nick
                    I could never understand why Parasets were so heavy, badly performing and risky. Surely you want a non-oscillating sensitive receiver in as light a case as
                    Message 9 of 18 , May 4, 2011
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                      I could never understand why Parasets were so heavy, badly performing and risky.

                      Surely you want a non-oscillating sensitive receiver in as light a case as possible, cheap, easy to operate, adaptable and versatile; with a good transmitter. The Paraset doesn't seem to fit well with this. I can only posit it was because it was chosen by the military who are well known for making bad decisions, often politically motivated.

                      Twisted heater wires and sensible component placement eliminates almost all audible hum. I have never found a requirement for heater DC. You can centre-tap the heater supply for best results as Quad does: www.drtube.com/schematics/quad/quad-22.gif

                      Nick on4Nic
                      Brussels

                      --- In regenrx@yahoogroups.com, "Prof. Arnaldo Coro Antich" <coro@...> wrote:
                      > The risky use of PARASETS in the field during World War II required a
                      > 6V filament battery and a vibrator for the high voltage!
                    • Paul Christensen
                      Many thanks to all who provided their insight on this matter, both on this list and through private replies. This topic seems to have received much attention
                      Message 10 of 18 , May 4, 2011
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                        Many thanks to all who provided their insight on this matter, both on this list and through private replies. This topic seems to have received much attention back in the late '20s as receiver technology was migrating from DC to AC power supplies.

                        Paul, W9AC

                        [Non-text portions of this message have been removed]
                      • davidpnewkirk
                        ... I dunno. Something in the system had to oscillate because CW Morse code was the necessary mode. Fewer tubes = fewer failure modes, lower battery drain and
                        Message 11 of 18 , May 4, 2011
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                          --- In regenrx@yahoogroups.com, "Nick" <Nick@...> wrote:
                          >
                          > I could never understand why Parasets were so heavy, badly performing and risky.
                          >
                          > Surely you want a non-oscillating sensitive receiver in as light a case as possible, cheap, easy to operate, adaptable and versatile; with a good transmitter. The Paraset doesn't seem to fit well with this. I can only posit it was because it was chosen by the military who are well known for making bad decisions, often politically motivated.

                          I dunno. Something in the system had to oscillate because CW Morse code was the necessary mode. Fewer tubes = fewer failure modes, lower battery drain and fewer potential replacement parts. RF stages cost complexity and energy. An RF-stageless superhet can be a potent radiator; an RF stageless oscillating regen near critical regeneration likely radiates less energy. Adding an RF stage to either would add complexity, battery drain and weight; and then a superhet would also need a BFO or an oscillating detector--*two* oscillators to DF, now.

                          BTW, it's a number I've mentioned here before, but again for the record the TRF regen I described in September 1992 *QST* radiated just 12 picowatts at normal regeneration. Do the math and you realize that an RF stageless diode-DBM solid-state direct-conversion receiver radiates its LO (often 7 dBm as applied to the mixer) several orders of magnitude more strongly.

                          It's easy to second-guess the past. And yet somehow, whatever our hand-wringing, the Axis lost anyway. :-)

                          Best regards,

                          Dave
                          amateur radio W9VES
                        • ku8h
                          Hi Nick, Radios like the paraset had to survive bumpy airplane rides, parachuting to the ground, maybe beach landings instead of airplanes, runs through the
                          Message 12 of 18 , May 4, 2011
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                            Hi Nick,

                            Radios like the paraset had to survive bumpy airplane rides, parachuting to the ground, maybe beach landings instead of airplanes, runs through the woods, tossing into a hidey hole. The ones sitting in my shack could never ever survive any of that (except maybe the RAK). Resistance fighter would have to "play rough" - not like our "Field Day" operations. The parasets seem to have done their jobs.

                            See other replies about other features.

                            73,

                            Bill KU8H
                          • ERNST
                            I suggest to connect the A voltage (for the filaments) to a positive tension ranging from 30 to 50 volt. This tension is easily obtained with a voltage divider
                            Message 13 of 18 , May 4, 2011
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                              I suggest to connect the A voltage (for the filaments) to a positive tension ranging from 30 to 50 volt. This tension is easily obtained with a voltage divider (2 resistors) of the B voltage (high tension).

                              Olivier
                              F5LVG

                              --- In regenrx@yahoogroups.com, "Paul Christensen" <w9ac@...> wrote:
                              >
                              > I am looking to reducing power supply hum in an audio stage. Presently,
                              > the chassis is used for the common filament return and accordingly, the
                              > chassis contains much 120 Hz current. From what I can measure, hum is being
                              > induced from the filament to the grid and cathode of a 6AQ5 and 12AU7 AF
                              > pre-driver.
                              >
                              > I am thinking of elevating the return filament from these two tubes and
                              > running the return with an insulated wire direct from the transformer.
                              > While 120 Hz current is still on the chassis, I may be able to reduce the
                              > effects of hum coupling. Another thought includes the use of 100-ohm
                              > potentiometer with a grounded tap to the chassis for use as a so-called "hum
                              > balance" control.
                              >
                              > Anyone care to share their experiences with getting rid of filament-induced
                              > power supply hum? Many Tnx!
                              >
                              > Paul, W9AC
                              >
                            • Hue Miller
                              Re the selection of tube series for spy radios, I do not think ruggedness of indirectly heated tubes was a big consideration. Consider that ALL portable combat
                              Message 14 of 18 , May 4, 2011
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                                Re the selection of tube series for spy radios, I do not think ruggedness of indirectly heated
                                tubes was a big consideration. Consider that ALL portable combat type radios used the
                                direct heated (cathodeless, directly heated filamentary types), in order to make portable
                                battery operation possible.
                                The spy radios were often rushed into production and as limited-production items I believe
                                they were sometimes somehow shorted on the design and test process.
                                Also you have to recall how long ago they were designed. There were not a lot of miniaturized
                                components available.
                                I have seen a Japanese WW2 radio, US intelligence bulletins name it the “Handy TM” ( Tokyo
                                Musen ) which uses 2 tubes in a power VFO / regenerative receiver with the tubes switched
                                between the two circuits, a really antique way, I suppose, of saving tube cost. I mean, the tube
                                is basically switched between 2 separate circuits. There is wide tuning range with miserable
                                dial resolution, no voltage stabilization for the single tube transmitter, no sidetone. How on
                                earth could they communicate with that??? --“Somehow !!”.
                                -Hue Miller

                                [Non-text portions of this message have been removed]
                              • dr_telecom
                                The WesKit BN4 was a kit transceiver of the 50s/60s that used a single 3A5 tube for both transmit and receive and was switched between the two by a big
                                Message 15 of 18 , May 6, 2011
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                                  The WesKit BN4 was a kit transceiver of the 50s/60s that used a single 3A5 tube for both transmit and receive and was switched between the two by a big multi-section switch. It was regen receiver/audio amp and stal osc/amp and ran off batteries.

                                  http://home.comcast.net/~sheldon_wh/bn1.html


                                  Primitive

                                  CQ Magazine had an article on the Japanese spy radio about a year or two ago. Primitive, but when you had to talk 10-20 miles, it worked. Most spy radios and most combat radios only had to talk a short distance and HQ likely had good antennas and decent power so you didn't need much of a set. Saving the battery was more important....fewer tubes was less power.

                                  Even now, the troops in the Middle East go through millions of dollars in batteries a month for their combat gear, radios, high tech sensors, night vision goggles, etc. All Li-ON batteries.
                                • Hue Miller
                                  The Weskit BN-1 actually has very simple switching, a 2PDT switch. One section switches the crystal from grid-plate, Pierce oscillator, the other position
                                  Message 16 of 18 , May 6, 2011
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                                    The Weskit BN-1 actually has very simple switching, a 2PDT switch. One section switches the crystal from grid-plate, Pierce oscillator,
                                    the other position grounds the low end of the crystal. In this position, the crystal is capacitively coupled to the plate coil of the transmitter
                                    and a bit of signal “suck-out” from the regenerative detector provides a bit of calibration sense. The other section switches filament power
                                    between the two halves of the 2-section filament. That’s a very unusual switching idea, and I think the use of it with this unique dual
                                    section tube was copied from the WW2 survival radio CRC-7. ( Just my notion; no actual documentation. )

                                    Some of the quite simple spy radios actually covered good distances. I’m thinking of the “Red Orchestra” operating from Switzerland
                                    to Mosow, Russia, in WW2; or another Russian spy, Sorge, operating from Tokyo to Moscow with a simple transmitter using a type
                                    10 tube. I am sure the receiver in both cases was regenerative.
                                    -Hue Miller


                                    From: dr_telecom
                                    Sent: Friday, May 06, 2011 11:34 AM
                                    To: regenrx@yahoogroups.com
                                    Subject: [regenrx] Re: Reducing VT Audio Hum REAL PARASETS USED 6 VOLTS ACCUMULATORS !!!


                                    The WesKit BN4 was a kit transceiver of the 50s/60s that used a single 3A5 tube for both transmit and receive and was switched between the two by a big multi-section switch. It was regen receiver/audio amp and stal osc/amp and ran off batteries.

                                    http://home.comcast.net/~sheldon_wh/bn1.html

                                    Primitive

                                    CQ Magazine had an article on the Japanese spy radio about a year or two ago. Primitive, but when you had to talk 10-20 miles, it worked. Most spy radios and most combat radios only had to talk a short distance and HQ likely had good antennas and decent power so you didn't need much of a set. Saving the battery was more important....fewer tubes was less power.

                                    Even now, the troops in the Middle East go through millions of dollars in batteries a month for their combat gear, radios, high tech sensors, night vision goggles, etc. All Li-ON batteries.






                                    [Non-text portions of this message have been removed]
                                  • Hue Miller
                                    I was just looking at the schematic for the German radio Ha5K39b. This is an AM-MCW-CW transmitter-receiver from WW2. I think the nomenclature means, Hagenuk
                                    Message 17 of 18 , May 8, 2011
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                                      I was just looking at the schematic for the German radio Ha5K39b. This is an AM-MCW-CW
                                      transmitter-receiver from WW2. I think the nomenclature means, Hagenuk (manufacturer)
                                      5 watt, short wave, 1939. I have seen a photo of it in use in a German E-boat which I believe
                                      was their equivalent of the US “Motor Torpedo Boat” ( PT ). Anyway, the circuit is surprisingly
                                      lean. An MOPA transmitter: osc – RF amp – modulator, 3 tubes. 3 tubes also for the receiver:
                                      RF, detector, audio. I think much of European produced electronics, for at least up to the late
                                      1950s, tended to be leaner and in less of supply than the situation in USA and Canada, and
                                      maybe even Latin America. Contrast the Ha5K39b with the US Navy’s standard 40 watt
                                      input, superhet receiver, 3 bands 1.5- 12 MHz radio TCS. BTW, the German radio is also
                                      single –band. The German receiver does have a rather involved input circuit; before the
                                      grid of the RF tube, there are 2 link-coupled tuned circuits ( 3 gang capacitor total )
                                      and also an antenna tuning control. Also voltage regulator tube.
                                      -Hue Miller

                                      [Non-text portions of this message have been removed]
                                    • jim_kr1s
                                      ... Not sure how relevant this is to regens, but as far as military equipment goes, there are two lines of thought, and which one you choose depends on your
                                      Message 18 of 18 , May 9, 2011
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                                        --- In regenrx@yahoogroups.com, "Hue Miller" <kargo_cult@...> wrote:
                                        >I think much of European produced electronics, for at least up to the late 1950s, tended to be leaner and in less of supply than the situation in USA and Canada, and maybe even Latin America.

                                        Not sure how relevant this is to regens, but as far as military equipment goes, there are two lines of thought, and which one you choose depends on your available resources. USSR MiG fighters tended to be lean and mean, with less attention paid to pilot comfort, for one thing, than U.S. fighters. But they were also less expensive than ours, so they could build a lot of them.

                                        I recall an interview with a U.S. Army tank commander, when the Abrams tank first came online. The Abrams was touted as being equivalent to, I think, four USSR tanks. When asked about this, the commander said, "My nightmare is that I look through the scope and see five Russian tanks."

                                        Homebrew radios tend to follow the lean-and-mean approach. Most home-builders I know are more interested in performance than having a bunch of blinkenlights. They're less convenient to fly and require more input from the pilot, but to us, those are features, not bugs.

                                        73,

                                        Jim, KR1S
                                        http://kr1s.kearman.com/
                                        http://qrp.kearman.com/
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