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SSB Carrier Supression

Discussion in 'General Electronics Chat' started by Space Varmint, Dec 3, 2008.

  1. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Nope - it's just a paper folding art! :D

    As part of the NVQ level 2 coaching course we had to teach something to a portion of the class (while the rest watched), and it was strongly suggested that we choose something other than martial arts.

    I choose Origami, my chief instructor taught a game we do with the kids (which none of the other instructors had ever seen), and EVERYONE else taught martial arts, mostly kata's or set's - depending on their style.

    One bright young 'prat', who came in a multi-coloured gi, tried to teach breaking boards - this to a room full of dan grades all higher than him, we all told him where to stick his boards, we've got more sense than that :D
     
  2. Space Varmint

    Space Varmint New Member

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    Hey flat5? How's your receiver coming?

    I'm busy with some stupid old code right now. :mad:

    So what ya got going? You sweeping that filter yet?
     
  3. Space Varmint

    Space Varmint New Member

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    When you figure out how to make PC boards with origami, do let us know. ;)
     
  4. dave

    Dave New Member

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  5. audioguru

    audioguru Well-Known Member Most Helpful Member

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    There is another topic here about a hearing aid that has an extremely narrow audio bandwidth and very high distortion like this SSB project.
    Its bandwidth is from 120Hz to about 300Hz.
     
    Last edited: Apr 9, 2009
  6. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Never made PC boards - and I suspect if I try folding veroboard it's going to snap :D
     
  7. flat5

    flat5 Member

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    Hi SV! I'm going very slow...too slow.
    Futurlec only shipped half my last order.
    They thought they had shipped it all!
    I'm waiting for experimenter boards and trimmer caps.
    Still have to order toroid cores and wire.

    Would someone please recommend Dual Gate Fets for RF amp and mixer for 3 to 20 mhz. Best for me is something that Futurlec has in stock or is very common.

    I also need to get air variable tuning caps.
    Then I will try some circuits.
     
    Last edited: Apr 9, 2009
  8. Space Varmint

    Space Varmint New Member

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    I looked in an older ARRL handbook and they listed a "40673" but I could not find it in on Datasheet catalog for integrated circuits, diodes, triacs, and other semiconductors, view

    An FET would have a higher impedance. Could be prone to pick up noise. The mixer is so important and often times non-active mixers are recommended because of the gain loss. I myself like a BJT. I have had great success with common 2N3904's. Though diode rings also do very well and come highly recommended. Some 1N914's work rather nice.

    I am happy to share this one I created with you. The output is taken off Q2 and the rf input goes to the base of Q2. The local osc. input is marked. You can control the gain with the emitter bypass caps. I found they should be the same value for both transistors. The transistors share a .37 inch ferrite core. I use Amidon FT-37-43 It works very well for me. You might want to try it.

    Did you make yourself a simple VFO yet?
     

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  9. Sceadwian

    Sceadwian Banned

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    Ewww. You ordered from Futurelec? Cheap stuff, but some of the worst customer service I've ever been victim too. Is this your first order from them? If it is get used to getting the run around, stuff on backorder can take weeks or longer.
     
  10. flat5

    flat5 Member

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    Third order from Fururlec. First went perfect. Second went well but a DVM had two problems. I told them and they said they would ship a new meter right away. They did not. I made a third order a month or two later and asked that they include the meter with that order. In six days I received the order but only half of it! The meter was included, free. I told them about the missing parts. They said they will ship them "as soon as possible". That was a week ago and I reminded them today to ship the parts to me. Actually, I asked them if they have shipped the parts.

    SV, no VFO yet. Have to order coil forms and wire.
     
  11. Space Varmint

    Space Varmint New Member

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    I think you said you don't have a signal generator. You could use this VFO for one. It has a very wide range and is quite stable, runs very cool. You could use just wire for the coil. I have made some with a thicker gauge, say around 26 and wound on a round pill bottle. Then rub some Elmer's glue on it and let it dry, then slide it off. The tap should be about one third from hot side of coil for maximum range. Just something to give you a head start. You can use any small signal JFET. I used a 2n5486. This circuit is very universal and will work well as your main tune and BFO and or 2nd local oscillator.
     

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  12. flat5

    flat5 Member

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    Thank you, SV.
    I'll run it in a sim and play with it.
     
  13. flat5

    flat5 Member

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    SV, what reactance am I looking for for L1?
    or the FET source impedance range.
    I need something to get me started choosing components for the tuned circuit.
     
  14. flat5

    flat5 Member

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    Playing around with SV's VFO, what I have so far.
    The two caps under L1 & L2 only provided parasitics.
    They did not affect the wanted frequency. Since a buffer would be used after the osc. R1 can be much higher in value than 60 ohms (50+10) for a greater swing.
    This should also allow a smaller coupling cap to the buffer.
    For the buffer I'm thinking of another FET (for now).

    I've played with all the components and the frequency, wave shape and gain (except R1) are almost completely dependent on L1 & L2. Putting caps across either one or both only causes problems. A small C2 works best and only 1M works for R2.

    The wave shape is terrible! I can't manage to improve the upper part of it. It remains flat no matter what I've tried. What I guess is needed is better DC biasing of the FET. I have done no designing of FET amp or osc. circuits.
     

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  15. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    Well, although I've no confidence that anything SV throws together would be any good, and I've not tried this circuit, you appear to have changed it considerably from the circuit he showed.

    L1 and L2 aren't separate coils, they are a single tapped coil, and the circuit operation is heavily dependent on that - also you have added a resistor in the drain, and taken the output off there, rather than the source, and a 5pF looks way too small for the capacitor feeding the gate.

    I've no idea what configuration it's supposed to be, it looks like a combination of a number of different configurations (half Hartley and half Colpitts perhaps?) - don't really see why he didn't just use one of the number of existing correctly designed VFO configurations?.

    Personally I've always been fond of the Colpitts design, as you don't need a tapped coil.

    Did a quick google:

    http://www.interalia.plus.com/q_tech9.htm
     
    Last edited: Apr 11, 2009
  16. flat5

    flat5 Member

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    Your right, Nigel, it is so different than what he suggested that I can not call it SV's VFO.

    I will try his circuit again if I can get Proteus to give me a tapped inductor. I did not find one so used two iductors in series.
    Why is that illegal? Something to do with mutual inductance?
    I did not notice my mistake about not bypassing the drain and taking the signal from the source. Very sloppy!
    The 5pf worked well. Tried many values. 3pf did not work.
    100pf or 50pf did not work better.
     
    Last edited: Apr 11, 2009
  17. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    A tapped inductor is a transformer, two inductors in series isn't a transformer.

    It's the fact it's a transformer that makes a Hartley type oscillator work.

    As you don't have a transformer in the circuit it's operation will be fairly random, I doubt it will have much simularity to real life either.
     
  18. JimB

    JimB Super Moderator Most Helpful Member

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    Hold on a minute, what worked well?
    Reality check here, this is not radio it is a computer game!
    Dump the simulator, get the soldering iron and some real components, connect them up on a breadboard* and try it for real.

    * Before the pack howls, I dont mean one of those things where components can be plugged in, although they are very useful in some areas, a mean a sheet of plain copper clad board.
    Try some "ugly construction" or "Manhatten", very effective for RF prototyping.

    JimB
     
  19. Nigel Goodwin

    Nigel Goodwin Super Moderator Most Helpful Member

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    I completely agree, never use them - they are of far too limited value.
     
  20. Sceadwian

    Sceadwian Banned

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    For a tapped inductor you need to specify some mutal capacitance between the two inductors, not sure what the coupling factor would be. I don't know how closely it will follow a real world inductor either. I've never had much luck inductor simulation in Spice.
     
  21. flat5

    flat5 Member

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    At this time I don't have any copper clad board. I'm waiting for 6 experimenter boards to arrive. I also don't have any coil wire.
    I can get these locally I guess so next week I'll go buy them.
    For now, sim is fun because osc. are new for me to "design".
    The colpitts will be easier to simulate.
     

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