A Few Pictures of the Southgate Type 7

Discussion in 'Homebrew and Kit Projects' started by N2EY, Oct 10, 2014.

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  1. N2EY

    N2EY XML Subscriber QRZ Page

    By request, here's some more detail of my homebrew 100 watt CW transceiver:

    GEDC0552.JPG

    Here's the main parts of the rig. The unit on the bottom with the big knob is the receiver section. To its left is the TR control box. Above it the big unit with the two round meters is the transmitter section, and the small chassis to the left is the transmitting mixer adapter.

    GEDC0553.JPG

    Below is a closeup of the receiver section. It's a 13 tube single conversion superhet with premixer for 80, 40 and 20 CW. 6EH7 RF amplifier, 7360 mixer, 6EH7 first IF, 6BA6 second IF, 6GX6 product detector/BFO, 6C4 first audio, 12BH7 audio output, 6C4 sidetone oscillator, 6AU6 heterodyne oscillator, 6BE6 mixer, 12AU7A VFO, 6BA6 VFO buffer.

    GEDC0554.JPG

    Closeups of the dial:

    GEDC0549.JPG GEDC0550.JPG

    The transmit mixer uses a 6AU6 oscillator and 6BA7 mixer to provide transceive capability:

    GEDC0539.JPG

    The signal from the transmit mixer is amplified to the 100 watt level by the transmitter section - a 12BY7A driving a pair of 807s:

    GEDC0545.JPG

    To power all this there are two supplies. The receiver and transmitting section are powered by a small supply that lives under the desk on a shelf. 5U4G rectifier, 0A3 and 0D3 regulators:

    GEDC0542.JPG

    The transmitter section is powered by the big supply. It's actually three power supplies on one chassis:

    Bias supply - 5Y3GT rectifier, 0C3 and 0D3 regulators to produce -45 volts bias

    Driver supply - 5Y3GT rectifier

    Final supply - two 866A rectifiers, two 0D3 regulators.

    GEDC0543.JPG GEDC1236.JPG

    All of this was homemade from available parts in the early 1990s. Almost nothing was bought new. Emphasis was on getting ti to work, not appearance. The Type 7 has performed well for 20 years (so far).

    The story of how the rig came to be was published in Electric Radio for July 1995, page 24
     
    K7LZR, N3AWS, W3KW and 18 others like this.
  2. N2EY

    N2EY XML Subscriber QRZ Page

    Here's how the rig works:

    The design came about because I found some nice crystal filters at a hamfest for a very low price. The rig was designed around them.

    The filters are 1400 kc. center frequency and 500 Hz bandwidth. No, I will not sell any of them.

    The main interest here is 80/40/20 CW, so the following was worked out:

    The receiver is single conversion - 6EH7 RF, 7360 mixer, first crystal filter, 6EH7 IF, second crystal filter, 6BA6 IF, 6GX6 product detector/BFO, 6C4 audio, 12BH7 audio.

    The VFO tunes 4900 to 5150 kc. using a 12AU7A. Its signal goes to a 6BE6 premixer and then to the 7360 mixer.

    The 6BE6 mixer also gets the output of a 6AU6 heterodyne oscillator (crystal controlled).

    On 80 meters, the heterodyne oscillator is disabled, and the 6BE6 premixer simply acts as a buffer amplifier. The VFO range of 4900 to 5150 kc gives a tuning range of 3500 to 3750 kc.

    On 40 meters, the heterodyne oscillator is on 3400 kc. and the 6BE6 premixer adds that signal to the VFO signal to get output of 8300 to 8550 kc., which gives a tuning range of 6900 to 7150 kc.

    On 20 meters, the heterodyne oscillator is on 7600 kc. and the 6BE6 premixer adds that signal to the VFO signal to get output of 12500 to 12750 kc., which gives a tuning range of 13900 to 14150 kc.

    Thus the CW parts of all three bands are covered on receive.

    The VFO signal is also sent to the transmitting mixer chassis, where it is mixed with the signal from a 6AU6 crystal oscillator by a 6BA7 mixer.

    On 80 meters, the transmit heterodyne oscillator is on 1400 kc. and the 6BA7 mixer subtracts the 1400 kc. from the VFO range of 4900 to 5150 kc to give a tuning range of 3500 to 3750 kc.

    On 40 meters, the transmit heterodyne oscillator is on 2000 kc. and the 6BA7 mixer adds the 2000 kc. to the VFO range of 4900 to 5150 kc to give a tuning range of 6900 to 7150 kc.

    On 20 meters, the transmit heterodyne oscillator is on 9000 kc. and the 6BA7 mixer adds the 9000 kc. to the VFO range of 4900 to 5150 kc to give a tuning range of 13900 to 14150 kc.

    The result is a transceiver, with the transmit frequency controlled by the receiver VFO.

    To permit RIT, a small hermetically-sealed relay in the VFO selects either a fixed silver mica capacitor or a variable capacitor of several hundred pf. The switching is done at a very low-impedance point of the tuned circuit, so it takes several hundred pF of variation to move the oscillator a few kHz. The relay coil is only energized when RIT is used, and then only on receive.
     
    KE4OH, N5OLA, KB1THM and 11 others like this.
  3. W0BTU

    W0BTU Ham Member QRZ Page

    Thanks! I enjoyed this. You have something to be proud of.
     
  4. AF6LJ

    AF6LJ Ham Member QRZ Page

    Nice, looks good, any plans to build a solid state version??
     
    KB9LXP likes this.
  5. N2EY

    N2EY XML Subscriber QRZ Page

    Thanks.

    No plans whatsoever to build a sand-state version. Don't see any reason to. I do have ideas for an improved version, to be known as the Type 8, but it's still in the planning stages. Paper is much cheaper and more abundant than aluminum.

    In fact the Type 7 uses no solid-state devices of any kind. (There are two 1N34As in the SWR bridge that is in the Transmatch, however).
     
    Last edited: Oct 10, 2014
    N3AWS and K1OIK like this.
  6. N2EY

    N2EY XML Subscriber QRZ Page

    Thanks!

    btw, not only is the rig homebrew, but the table, shelves and even the clock are too. The op table is an old solid-core office door, 36 inches deep and 6 feet long. Shelves and supports were made from salvaged wood. Nothing goes to waste.
     
    K1OIK likes this.
  7. KB2FCV

    KB2FCV Ham Member QRZ Page

    Jim, GREAT work! I love it! That must be a blast to use.
     
  8. AF6LJ

    AF6LJ Ham Member QRZ Page

    A little sand always manages to get in somewhere.

    ;)
     
  9. K5UOS

    K5UOS Ham Member QRZ Page

    I have followed your references to this station for quite some time. It is really nice to see more of it up close.

    Thanks for showing it.

    I still remember the photo of your tuning mechanism that uses a bowl (am I correct?) for the rotating dial. It was on the HBR site.

    Note:

    Price all those bakelite knobs on ebay or other places. I am glad I have collected them for years.

    I like the idea of the frequency offset you use by shifting the VFO on transmit. I do something similar but with a stand alone, free running homebrew VFO. I mix tube and solid state whenever it is useful.

    [​IMG]
     
  10. N2EY

    N2EY XML Subscriber QRZ Page

    You're welcome. More to come...

    That was in one of the Southgate Type 4 receivers. Yes, it was a plastic cereal bowl. The Type 7 uses a piece of plexiglass pipe as a drum dial.


    So am I.


    The reason for building a transceiver is so that, in contests, there's no need to spot the transmitter. Really helps the QSO rate in S&P operations.

    I looked long and hard for a decent 100 watt output hollow-state American made CW transceiver, and could not find one. So I started building them.

    Requirements:

    - Sharp CW filtering (500 Hz max)

    - 100 watts output on 80/40/20

    - slow tuning rate (less than 10 kHz/turn) and good feel

    - AGC OFF switch

    - RIT

    - 100 watts output from real transmitting tubes, no sweeps

    - Match reasonable SWR without a tuner

    - Serviceable with simple tools and test equipment

    - Inexpensive
     
    W9JEF, N3AWS, WA9WVX and 1 other person like this.

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