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Sensitivity of TBY-8

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  • Richard Hankins
    Folks, just found this group by researching the TBY sets. I am interested in the performance of early VHF sets, and the TBY is an excellent example. One
    Message 1 of 5 , Jun 19, 2011
      Folks,

      just found this group by researching the TBY sets.   I am interested in the performance of early VHF sets, and the TBY is an excellent example.   One key spec is sensitivity, and this is one of the few that actually gives figures (you won't find them for things like the Hallicrafters S-27 for instance).

      The spec in the TBY-8 manual is very well hidden in section 6-21 (3) "Sensitivity Adjustment".  What is says is that up to 65Mc/s, the sensitivity is 5uV (or better) for an audio S/N ratio of 6dB, where the input signal is 30% AM at 400c/s.  

      Can anyone who has manuals for other sets in the TBY series tell me whether this is a general spec - or whether they vary?

      best regards


      Richard
    • ke5o_steve
      Welcome to the group Richard! I set up two TBY-8 s and measured the rx sensitivity as.. Serial # s/n @ 5uv 10uv 1927 9 Db 14 Db 2392
      Message 2 of 5 , Jun 23, 2011
        Welcome to the group Richard!

        I set up two TBY-8's and measured the rx sensitivity as..

        Serial # s/n @ 5uv 10uv

        1927 9 Db 14 Db

        2392 8 Db 12 Db

        52 Mc/s 30% AM @ 1000 c/s on HP 8656B gen and an HLI test set across the headphones with TUNING, REC ANT, and REGEN peaked for best s/n.

        73,

        Steve

        --- In code_talker_radio@yahoogroups.com, Richard Hankins <richard.hankins@...> wrote:
        >
        > Folks,
        >
        > just found this group by researching the TBY sets. I am interested in
        > the performance of early VHF sets, and the TBY is an excellent
        > example. One key spec is sensitivity, and this is one of the few that
        > actually gives figures (you won't find them for things like the
        > Hallicrafters S-27 for instance).
        >
        > The spec in the TBY-8 manual is very well hidden in section 6-21 (3)
        > "Sensitivity Adjustment". What is says is that up to 65Mc/s, the
        > sensitivity is 5uV (or better) for an audio S/N ratio of 6dB, where the
        > input signal is 30% AM at 400c/s.
        >
        > Can anyone who has manuals for other sets in the TBY series tell me
        > whether this is a general spec - or whether they vary?
        >
        > best regards
        >
        >
        > Richard
        >
      • Richard Hankins
        Steve, Thanks very much for the welcome - and thanks very much for giving me some useful data. These figures show your two sets more than meet the
        Message 3 of 5 , Jun 29, 2011
          Steve,

          Thanks very much for the welcome - and thanks very much for giving me
          some useful data.

          These figures show your two sets more than meet the specification in the
          handbook. Sometimes I have found early performance figures
          (particulary transmitter RF power output!) to be impossibly inaccurate -
          but in this case it shows a 5uV sensitivity figure to be about right.

          The reason I asked is that I am researching a British spyset - the TRD -
          which has a very similar circuit design to the TBY. Their receivers
          both have an untuned RF amplifier, followed by a super-regenerative
          detector, and completed by an audio amplifier. I am not quite sure
          whether the TRD super-regen was self-quenching (as in the TBY) or had a
          separate quench oscillator (using one of the transmit valves), but that
          is a subtlety which I don't think is immediately important.

          The trouble is that no-one can measure a TRD's performance, because none
          now exist. At the end of WWII, Churchill ordered they all be rounded
          up, and thrown down a mine-shaft and covered over with lots of
          concrete. The only person who knows where the mineshaft is now 96 and
          he's still not saying......

          You may have heard that the British destroyed their computer industry at
          birth, by doing the same thing to the very first programmable computer
          used at Bletchley Park to break the Enigma codes - well the TRD got the
          same treatment. What was in the TRD to make it quite so sensitive is
          something I am working on.........plainly there was more to the set than
          just a simple super-regen system!

          However, the sensitivity figures are very useful in another way. The
          TRD was used in a very extensive network of VHF links, which stretched
          all around the British coast, from West Wales, through England, to the
          north of Scotland (think of it anti-clockwise). This was almost
          certainly the first really big VHF network in the UK ( I dont know
          whether the US had anything earlier). The trouble is that a lot of
          the claimed links look impossible with the known sensitivity figures of
          other VHF sets - for instance, the R1132A VHF receiver has a sensitivity
          of 20uV - and the surprising thing is that it is a 11-valve superhet!

          So, the TBY is a very useful benchmark to establish just what this type
          of circuit (which TBY and TRD share) is capable of. A 5uV figure -
          which is 12dB better than the R1132A - will make the link sums look very
          different!


          thanks a lot



          Richard
          G7RVI

          On 23/06/2011 19:32, ke5o_steve wrote:
          > I set up two TBY-8's and measured the rx sensitivity as..
          >
          > Serial # s/n @ 5uv 10uv
          >
          > 1927 9 Db 14 Db
          >
          > 2392 8 Db 12 Db
          >
          > 52 Mc/s 30% AM @ 1000 c/s on HP 8656B gen and an HLI test set across
          > the headphones with TUNING, REC ANT, and REGEN peaked for best s/n.
        • ke5o_steve
          Fine Business Richard! I fully understand where your 96 year old friend is coming from, it s like the code talkers honored here, their word was un-breakable
          Message 4 of 5 , Jun 30, 2011
            Fine Business Richard!

            I fully understand where your 96 year old friend is coming from, it's like the code talkers honored here, their word was un-breakable and that was simply that.
            I have fun communicating between the TBY and a Heathkit "Sixer" also utilizing a self quenching detector. I do believe the TBY has a tuned RF stage ahead of the detector though (V1 959)?
            Another area of interest for me is the AN/PPN-1 Eurica beacon tranceiver (transponder) which used the 9000 series 7 pin miniature tubes with a regenerative RX near 200 Mc/s.
            I just finished reading the fascinating book "Battle of Wits" by Stephen Budiansky and he provided excellent documentation of the Allied effort of codebreaking in WWII. We owe a lot to people of true genius.
            Good luck in your pursuits of the TRD, the Polish built a functioning Enigma machine years before the war ever started without having ever seen one! Your task may be similar.
            73,
            Steve
          • Richard Hankins
            Steve, Yes, many thanks for doing that test for me. You are quite right about the tuned RF stage - I went back to the schematic, and there is it: a tuned
            Message 5 of 5 , Jul 2, 2011
              Steve,

              Yes, many thanks for doing that test for me. You are quite right about
              the tuned RF stage - I went back to the schematic, and there is it: a
              tuned circuit between the aerial input and the RF amplifier grid 1.
              The tuning capacitor must be ganged with the super-regen detector tuning
              - its sort of shown on the diagram but its not immediately obvious due
              to the way its drawn.

              I didn't know the PPN-1 used a super-regen detector - I will have to
              look into that - thanks for pointing that out!

              The breakthroughs in WWII were quite astonishing - though they probably
              aren't what many people remember WWII for. The key breakthroughs seem
              to have been:

              * Generating many kWs of RF output at 3GHz with the magnetron for
              H2S radar - which enabled airborne navigators to see the ground
              for the first time
              * Radar itself was a key breakthrough, though in fact it came before
              the war in the 1930s, it was the threat of war that forced the
              high speed development.
              * the first true transceiver, where you could tune both the receiver
              and transmitter with one tuning knob - that was in the Wireless
              Set No.11
              * the use of VHF in sets like the TBY, the Wireless Set 17 and 36,
              and many other sets, thus opening up a lot more MHz to play with
              (the Germans were far in advance of the Allies in using the VHF bands)
              * Systems to allow radionavigation, like GEE, which let airborne
              navigators work out where they were without transmitting at all
              (which allowed the enemy to DF them and then target them)
              * The Germans invented ferrite cores which enabled high Q inductors
              in a small space.
              * The Germans pushed the use of cast alloys for set cases, which
              made the electronics a great deal more stable and able to resist
              nasty things like humidity - the first set in the UK was the
              Wireless Set No.42 - I am not sure when the Americans caught up
              with this.
              * introducing FM as a better modulation system than AM - this
              started at HF in the UK, but the Americans really made a
              breakthrough here with their BC-1000 manpack transceiver, which
              revolutionised short(ish) range comms at D-Day and afterwards.

              That's quite a list though I expect I have missed something.

              I don't know whether the TBY was the first VHF set for the Americans or
              even amongst the first. I have heard that Motorola had provided the
              police in the US some mobile radios before WWII, but I have always
              assumed they were high HFat 20 - 30MHz, rather than true VHF above
              30MHz. The Americans pioneered the acorn valves in the 1930s so there
              must have been quite a lot of uses for them before WWII.


              best regards


              Richard


              On 01/07/2011 04:26, ke5o_steve wrote:
              >
              > Fine Business Richard!
              >
              > I fully understand where your 96 year old friend is coming from, it's
              > like the code talkers honored here, their word was un-breakable and
              > that was simply that.
              > I have fun communicating between the TBY and a Heathkit "Sixer" also
              > utilizing a self quenching detector. I do believe the TBY has a tuned
              > RF stage ahead of the detector though (V1 959)?
              > Another area of interest for me is the AN/PPN-1 Eurica beacon
              > tranceiver (transponder) which used the 9000 series 7 pin miniature
              > tubes with a regenerative RX near 200 Mc/s.
              > I just finished reading the fascinating book "Battle of Wits" by
              > Stephen Budiansky and he provided excellent documentation of the
              > Allied effort of codebreaking in WWII. We owe a lot to people of true
              > genius.
              > Good luck in your pursuits of the TRD, the Polish built a functioning
              > Enigma machine years before the war ever started without having ever
              > seen one! Your task may be similar.
              > 73,
              > Steve
              >
              >
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