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An Urban Legend Disproved

Discussion in 'Ham Radio Discussions' started by N2EY, Jan 1, 2015.

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  1. W9JEF

    W9JEF Platinum Subscriber Platinum Subscriber QRZ Page

    Is that what the original 20-A used?
    Nevertheless, I'd appreciate having the info.
    Can you email it to me? pi316@webtv.net

    About all that remains of my ARC-5 is a gear-driven tuning cap.
    Other than that, I'll be starting from scratch. There are probably
    more efficient frequency multipliers than those using 1625's. ;)
     
  2. N2EY

    N2EY XML Subscriber QRZ Page

    I'll just put it here for all to see:

    Probably the best-known of the phase shift networks (PSN)s was the B&W 2Q4/350, made by Barker and
    Williamson. These units were housed in a metal tube shell the size of a 6J5,
    and gave a 90 degree phase shift (plus or minus 1.5 degree) over the audio
    range of 300-3000 Hz. Many SSB projects in the '50s were designed around the
    2Q4/350.


    B&W actually told you what was inside! They figured most hams would not
    have the equipment to duplicate the PSN, anyway, and they were right. But
    today, with highly accurate DMMs being very common and PSNs very scarce, some
    may want to try their hand at building one.

    So here's what's inside, taken from
    a 1955 B&W data sheet.

    Pin numbers are the same as any octal tube.


    From Pin 1 to Pin 2: 680 uuf cap in series with 487K resistor
    From Pin 2 to Pin 3: 430 uuf cap in parallel with 770K resistor
    Pin 4 has no connection
    From Pin 5 to Pin 6: 680 uuf cap in series with 125K resistor
    From Pin 6 to Pin 7: 430 uuf cap in parallel with 198K resistor
    Pin 8 has no connection


    No precision is specified, but with 1% resistors and 5% capacitors readily
    available, it should not be too hard to get close enough. Note that there are
    only two capacitance values.


    In most designs, Pins 1 and 5 are connected together, and Pins 3 and 7 are
    connected together. Balanced audio from the secondary of a plate-to-line
    transformer feeds Pins 3 and 5, and output to the grids of the audio stages is
    taken from Pins 2 and 6.


    More!


    The RME 4301 SSB adaptor (meant for receivers) used a PSN, too. This one is in
    a rectangular metal box that's not sealed like the B&W unit. I have the data on
    what's inside one of those, too:


    From Pin 1 to Pin 4: 2430 uuf cap in parallel with 133K resistor
    From Pin 3 to Pin 4: 4860 uuf cap in seriesl with 94K resistor
    Pin 2 has no connection
    From Pin 5 to Pin 6: 1215 uuf cap in series with 94K resistor
    From Pin 5 to Pin 8: 607 uuf cap in parallel with 133K resistor
    Pin 7 is metal shell (ground)


    Note that the capacitors are all even integral multiples of each other. I don't
    know how this unit was supposed to be used.


    I don't have any of the PSNs, just the data. Hope someone can use this.
    Someday, I'll build one...


     
  3. W9JEF

    W9JEF Platinum Subscriber Platinum Subscriber QRZ Page

    Many thanks for the info, Jim.

    My old Handbooks show phase shift circuits,
    but with a much higher component count.
    I'm going to dig up my 20-A manual, and
    put your info there.

    Appreciate your taking the time to share that. :)
     
  4. KL7AJ

    KL7AJ Ham Member QRZ Page

    The math DOES work if you use a 9 MHZ UPPER sideband generator and a VFO from 5.0 to 5.5 MHz....a very common VFO scheme. If you ADD the vfo frequency you will get an upper sideband signal on 20 meters. If you SUBTRACT 5 MHZ from 9, you get an 80 meter LSB signal. (And the dial works backwards. :)
     
  5. K2XT

    K2XT Premium Subscriber QRZ Page

    Nah. USB on 4 MHz
     
  6. N2EY

    N2EY XML Subscriber QRZ Page

    No, it doesn't work. See post #1 in the thread. Do the math and you'll see.

    Yes, that's right. No sideband inversion going from 9 to 14 because all you did was add the VFO frequency to the USB frequencies.

    No you don't. The sideband does NOT invert!

    All that happens is that every frequency of the 9 MHz USB signal is decreased by the VFO frequency. No sideband inversion. None. Nil. Nada. Doesn't happen.

    The ONLY way you get sideband inversion when heterodyning is if BOTH the input and output frequencies are LOWER than the VFO frequency. IOW, the oscillator MUST be the HIGHEST frequency of the three frequencies (input, output, oscillator) involved for the sideband to invert.


    Yes, the dial works backwards. But that's all that inverts.

    Oh wait - I see a smiley.

    Is the whole post a joke?
     
  7. K9STH

    K9STH Ham Member QRZ Page

    The 350/2Q4 was used in the Johnson Pacemaker, Hallicrafters HT-37, Heath SB-10, as well as the Central Electronics 10, 10A, 10B, 20, 20A, and a lot of other phasing type SSB exciters/transmitters.

    The information on the 350/2Q4 is on the Heath SB-10 schematic.

    Somewhere, I have an original data sheet that came with the 350/2Q4 when the phase shift network was purchased separately from a piece of equipment.

    Glen, K9STH
     
  8. W9JEF

    W9JEF Platinum Subscriber Platinum Subscriber QRZ Page

    I agree... add or subtract 5 from the USB signal, it's still USB.

    Subtract the 5 to 5.5 VFO, and the dial does read bass-ackwards.
     
  9. W3WN

    W3WN Ham Member QRZ Page

    Jim,

    Can you PM me a direct E-mail? I have a newsletter to send to you.
     
  10. N2EY

    N2EY XML Subscriber QRZ Page

    To W3WN: Done.

    Here's another urban legend: the origin of 73
     
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