HR-10b Project

Discussion in '"Boat Anchor" & Classic Equipment' started by W7UUU, Feb 13, 2016.

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  1. N2EY

    N2EY Premium Subscriber QRZ Page

    No hurry.

    I have been known to take all the pieces of a project and put them in a labeled box so they don't go wandering off.....

    I owe you a sketch of how to get that 9 volts for the audio filter anyway.

    73 de Jim, N2EY
    Last edited: Apr 11, 2017
    WA2LXB likes this.
  2. W9GB

    W9GB Ham Member QRZ Page

  3. N2EY

    N2EY Premium Subscriber QRZ Page

    Most interesting!

    In particular, the first mixer uses the Pullen circuit, though it is not identified as such. The product detector is a 6JH8 beam-deflection tube, similar to the 7360 but lower-priced and more available.

    73 de Jim, N2EY
  4. W9GB

    W9GB Ham Member QRZ Page

    Good eye, Jim.

    Mr. Morgan described "The first mixer stage uses a rather unusual cathode-coupled circuit."
    In the footnotes of the receiver article, Keats Pullen's book is referenced !

    A Cathode-Coupled Triode Mixer (Pullen Mixer)
    excerpt from his book, Conductance Design of Active Circuits, John F. Rider Publisher, 1969.
    by Dr. Keats Pullen

    A Like New Mixer Circuit
    73 Magazine, October 1961 Like-New Mixer Circuit.pdf

    Another Look at the Like New Circuit
    A low distortion low noise mixer
    Magazine, August 1966

    Pullen Mixer from the RSGB “Radio Communications Handbook”, 4th Edition, 1972.
    Uses the 6AQ8/ECC85 vacuum tube Mixer from RSGB.pdf

    Last edited: Apr 13, 2017
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  5. W7UUU

    W7UUU Super Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Haha! Clever "bump" via the other thread ;)

    I did finally get most everything sorted out on the HR-10b and it works well on 40 and 20. But still dead on 80 due to that broken antenna input coil I mentioned a month or so ago in another thread. This project has taken a back burner for right now, with all the move and everything. But by Fall it will be paired with the DX-60b and HG-10b for sliding into winter time again, with [hopefully] all new antennas by then.

    I'll post up pix of the "Novice Corner: Heathkit Edition" soon - it looks pretty cool, and I even have the QSL card designed for it! See below...


    HR-10b DX-60b QSL Card Front.png
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  6. WA2LXB

    WA2LXB XML Subscriber QRZ Page

    Niiiice! My rigs are quietly awaiting attention. The L-4B and SA2060 rebuilds both got in the way. Are you going to do any AM work with the '60?
  7. W9GB

    W9GB Ham Member QRZ Page

    Dave -

    The happen to be looking at the Hallicrafters SX-122 schematic diagram.
    The SX-122 is a dual-conversion receiver,
    the two intermediate frequency (IF) stages at 1650 kHz and 50 kHz.
    Page 1 (schematic)
    Page 2 (schematic)

    The Heathkit HR-10(b) used a single IF stage at 1681 kHz.
  8. KM1H

    KM1H Ham Member QRZ Page

    Im a big Pullen fan and have converted several BA's to them and never disappointed. With a low noise mixer that radio might wake up on 20 but it will not be an easy job. Ive used 6SN7, 6J6, 12AT7, and 6ES8's. Modded my 75A4 to 7360's in both IF's before the Pullen appeared.

    With only 125VDC on most of the HR-10 a bit of a gain boost might help 20 and up. Try a 6GM6 in the RF amp and reverse wires to pins 2 and 7 and see what happens and then drop the cathode resistor to 56 Ohms to do the tube justice at that voltage. Try the 6BZ6 in the first IF with the same pin swaps.

    With some changes the SX-140 makes a nice AM and fair CW radio but not for the novice modder. I turned both of mine into double conversion with 262 and 455 IF's and other mods. Used one at a time at our summer place in Maine along with a modded was at a premium. Kids grew up, rigs and cottage sold.

  9. N2EY

    N2EY Premium Subscriber QRZ Page

    See post #39 for some ideas about dual conversion.

    The SX-140 kit cost $20 more than the HR-10 kit - $80 vs $100. A lot of money in 1962!
  10. N2EY

    N2EY Premium Subscriber QRZ Page

    After re-reading Post #39, and doing some thinking, here's what I'd do:

    1) To improve the performance on the higher bands, I'd build a simple crystal-controlled converter. Two tubes at most - one for the crystal oscillator, one for the mixer. A 6ES8 dual triode in the Pullen configuration could do the job well:

    Such a converter could add WARC band and WWV reception - just a matter of finding the crystals. With a single 3500 kc. crystal, 20 and 15 can be covered by using an overtone circuit (there's a QST converter that does this.)

    Using a converter with the receiver on 80 means the stability of the HR-10 on its best band is preserved. If the 6BJ7 triple diode and the 6X4 rectifier are solid-stated, the HR-10 should be able to power the converter easily.

    2) Add a VR-tube or Zener diode regulator for the HFO and BFO.

    3) If one can find crystals on or near 1681 kHz, modern ladder filters can be made which will improve selectivity greatly. They can be switched by small DIP relays. A subchassis with the filters and relays can be made that will fit in the space vacated by the first IF transformer and the crystals, so the receiver can be restored to original condition if desired.

    4) Audio selectivity can be added as an alternative or in conjunction with improving the IF selectivity.

    73 de Jim N2EY

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