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    • #6849
      Guenni75
      Participant

      I will try to post my very first schematic found in a magazine nearly 60 years ago. I have tried many times with not enough knowledge, no measurement instruments and a solder iron – what was a hot screw driver (!) – to assemble this circuit of this outstanding “double reflex superhet” what is not really exact… and all the years after the “best” result was bad noise and “breathing” current flow…

       

       

      1TransReflexSuperhet

      In 2018  I got the first good result with selected germanium PNP transistors, so I decided to develop a Lectron block with the required parts, even in mind that Georg F. Greger had similar ideas in 1966, as the magazine HOBBY reported in August 1966.

      My complete Lectron circuit look like this:

      and works good / with a local radio station or an AM Modulator fed with music from cassette, CD, PU or what ever source. Even a loudspeaker via  an output transformer can be used instead of the high impedance earphone.

      Any questions welcome…

       

    • #6861
      LectronFan
      Participant

      Hi !

      What a coincidence, I also grew up with AM radio receivers in their simplest forms !

      I remember my Science fair kit 150in1 kit with it’s Germanium transistors and simple crystal and reflex receivers.

      Later on, I used FET transistors and HF circuitry, followed by heterodyne receivers (Philips EE 2000 kit).

      Still now, I love to listen to AM radio sometimes, only receiving very distant stations, like UK, Italian, Spanish etc.

      I haven’t build AM radios with the Lectron set yet, I do have the AM receiver block (ZN414) and will try it for sure.

      Your circuit seems very cool, a mixture of the first stage of a heterodyne receiver with LF feedback.

      Did you use a printed circuit board or did you just made a wired cube ?

      The oscillator and IF coils, are these from a normal AM radio ?

      I will try to replicate your circuit (on a breadboard).

      Keep on posting those receivers ! I admire your skills in building customized blocks !

      Greetings

      • #6869
        mwpeters75
        Keymaster

        Hi Günther and Frank,

        This is great stuff, thank you for your contribution and willingness to share some of your other fascinating creations.

        Best,
        Michael

        • This reply was modified 3 weeks, 1 day ago by mwpeters75.
        • This reply was modified 2 weeks, 6 days ago by mwpeters75.
    • #6865
      Guenni75
      Participant

      Hi,

      all parts like double variable capacitor, ferrit antenna, oscillator coil, IF filter (colored red-yellow-white-black) are standard and can be taken from old and unused pocket radios – otherwise it will be noticed e.g. in my BOY’S RADIO coming up next because it uses nearly the same circuit but a “HF transformer”.

      For the wiring I use since many decades the so-called Veroboard (wholes  with 2.54 or 5.08 mm distance all over the “PCB” with copper eyes for soldering), suitable sized and wired underneath:

      This allows corrections and extensions without new design of the board. Critical circuits I use to test prior with the same material and with socket(s) for transistor(s) to select the best ones and to make additional experiments, here: using an output transformer for loudspeaker / second AF amplifier OR earphone usage only:

      The ferrite antenna / capacitor-block is designed for multiple usage. The advantage: both components are adjusted for best reception once and can be used anywhere else. Because of the need of low impendance input in transistor radios the similar block for my tube superhets (reflex & “normal”, steel or pencil tubes) is quite vice versa, which means that the LC circuit has to be connected to grid 1 of the first tube, and the coupling part is for antenna input.

      My circuits with the ZN414 (standard receiver and superhet applications) will come up, too… Be careful to use the ZN414 block because the IC only works with up to 1.5V (best: 1.3 V)!

      Therefore I created a special block just to be sure that NEVER any problem will occur … and why not integrate all and ever required parts for usage in this block, too?!

      I have a lot of stuff to introduce – please be patient 😉

       

      • #6873
        mwpeters75
        Keymaster

        Thanks so much Günther!

        As always, amazing and innovative!  Looking forward to seeing more from your workshop.

        Best,
        Michael

        • This reply was modified 2 weeks, 6 days ago by mwpeters75.
    • #6874
      Guenni75
      Participant

      … I forgot to explain that this circuit uses the converter twice (RF & AF) without IF amplifying – may be the amplification – depending on the location – is not sufficient: here are three versions of additional amplifier environments (sorry for the poor quality, but I haven’t found all the 3 old images on my actual PC – maybe a former HD crash – so I scanned a DIN A4 page with these printouts ):

      It’s a 1-stage-amplifier as one Lectron block with the cable/plug (instead of the earphone / earpiece) with an input transformer (which appears around 1965 in Lectron patents!) , one Ge-transistor and different loudspeaker combinations. The middle one is a special one and contains a “transformer” with one coil and a tap at 50Ω; for the speaker and a stereo socket for stereo headphones of 2 x 32Ω; wired for mono parallel. The third one uses a universal transformer and a special “crossing” block.

      Thanks for reading & don’t forget: all known and individual blocks at: http.//www.g-stabe.de/lectrony.htm

       

       

       

      • This reply was modified 3 weeks, 1 day ago by mwpeters75.
      • This reply was modified 3 weeks, 1 day ago by mwpeters75.
      • This reply was modified 3 weeks, 1 day ago by mwpeters75.
      • This reply was modified 3 weeks ago by mwpeters75.
      • #6887
        mwpeters75
        Keymaster

        Very engaging projects Guenther!  Mr. Greger would loved to have worked with both you and Frank 🙂 

        Best,
        Michael

    • #6878
      LectronFan
      Participant

      Hi,

      These are great diy radios !

      This is something I miss in the Lectron set : a transformer with center tap. So many inductive experiments can be performed with these and they are ideal for coupling transistor stages.

      Have you also checked my is ill at or circuits  ?

      I made use of the high tension transformer of the Base kit .

      As amplifier for your radio maybe the legacy preamplifier block could also be used.

      Greetings

       

    • #6900
      Guenni75
      Participant

      Hi,

      yes – you are right, I could have made use of the HV transformer and the 2-stage amplifier, BUT: I use Lectron at first as a pre-testing tool before I build a “normal” (none-Lectron)  version or a new Lectron block.

      In this case the limit of – total – 2 transistors was given by the BOY’S RADIO idea, more: see coming post. I had a lot of small transformers (and still have a couple of these) so to build a suitable Lectron transformer block is no problem. In this special case I had no free contact(s) for the AF output (or only diagonal, that’s bad…) so I first used the earphone socket. With a suitable plug + cable for a transformer-input it works, but I decided to built a separate block, so I don’t have to collect and place single blocks all over the ground plate just for testing another version – keep it simple!

      Transformers: the first Lectron transformer from G.F. Greger was described in a patent applicant May 7th 1965 (# 1,228,081 Germany). Gerd Kopperschmidt realized it with blocks #2710 and #2712. Around 1970 Max Guerth built two of these (with tap !), and Harmut Birett in the 1970s for his Physics class. The cover images can be found in my “Electronic Lectron Card File” at line 415, 417 (Lectron RWO), 455, 456 (Max Guerth) and 604 (Hartmut Birett). The total amount is about 900 so it may be a help for positioning the thumb scroll bar.

      Best,

      Günther

      • This reply was modified 2 weeks, 6 days ago by mwpeters75.
      • This reply was modified 2 weeks, 6 days ago by mwpeters75.
      • This reply was modified 2 weeks, 5 days ago by mwpeters75.
    • #7078
      LectronFan
      Participant

      Hi,

      This is a nice approach of using Lectron. First build of a circuit with separate components and then putting this circuit in 1 module.

      A while ago, I experimented and finished a HEX bcd decoder with 7 segment display.

      The only trouble I had was to cramp all components in a 3×1 module !

      So I had to trim the circuit and now it’s waiting to be build.

      So far I had tons of fun with only the basic and expansion set (see my circuit posts on the forum). I’d love to tweak and invent circuits with only the parts of this set.

      I haven’t even open the rest of the 1205 box !

      BTW, I checked your impressive list of all blocks ever made, never knew there were so many of them !

      Best wishes

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