favorite novice transmitter for about $100 these days...

Discussion in '"Boat Anchor" & Classic Equipment' started by K9UR, Oct 23, 2021.

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  1. KM1H

    KM1H Ham Member QRZ Page

    After I got the General in 56 I never used a crystal for HF again but did use the usual 8mc surplus rocks for VHF
     
  2. W9BRD

    W9BRD Ham Member QRZ Page

    Yes, like working to move its design toward RF literacy.

    George Grammer, W1DF, ARRL Technical Director, in his May 1962 "Recent Equipment" review of the T-60, had this suggestion for fixing a built-in stability issue:

    t-60_final_as_locked_oscillator.jpg
    The above issue is not a maybe; some years ago, a correspondent noted in an online Novice Rig forum that his T-60 was the only rig he had that allowed the use of 40 meter crystals on 80 -- a bug, not a feature!
     
    N2EY likes this.
  3. WA5VGO

    WA5VGO Ham Member QRZ Page

    No one has more respect for George Grammer than me, and I have no doubt he experienced exactly what he described. But I've got to say that I've owned several T-60's over the years and I never saw this. I suspect parts layout may be a big factor in whether or not the transmitter tries to take off.
     
  4. K1APJ

    K1APJ Premium Subscriber QRZ Page

    An addendum to the T-60 manual added a 27K resistor across RFC2, probably Knight's answer to the W1DF comment.

    I had a T-60 for a while, I was troubled by the lack of provision for plate current metering and no protective bias for the 6DQ6. Seemed like a bad combination.
     
    N2EY likes this.
  5. W9BRD

    W9BRD Ham Member QRZ Page

    They did build in mods later to address early rough edges: loading Rs to quell self-oscillation, a shield on the oscillator-driver tube (which sits in the near field of the final-amp output inductor) and insulation on the final-amp-output coil leads to curb sparking.

    What such mods can't fix is that the oscillator grid is separated from the crystal socket by a 9ish-inch-long piece of unshielded wire that passes by higher-level, later transmitter stages; and that the oscillator-driver tube should be mounted close to the front panel where the modulator tubes are, and vice-versa.

    And then there's

    t-60_parasitics.jpg

    -- not a strictly T-60 problem, but one built into the physics of the beam power tubes used for decades for RF power amplifiers, as I describe in my page at http://dpnwritings.nfshost.com/ej/beam_power_tube_parasitics/ . Screen and/or plate "stopper" Rs are worth adding to any amplifier, RF or AF, that uses such tubes, whether not we've (yet) noticed it producing interference by the mechanism described.
     
    K9UR likes this.
  6. W9BRD

    W9BRD Ham Member QRZ Page

    Well, then, as a consolation prize you'll appreciate that the T-60's designer in effect "protects" the 6DQ6 by hard-connecting a 2.2-k, 2-W resistor from the set's common cathode-keying line to common, causing the 6DQ6 (as well as the other stages) to draw several tens of mA of standing current all the time as a means of keeping the output of the set's voltage-doubler-based B+ supply from soaring too high.

    The absence of plate-current metering allowed such design mischief to pass undetected; just understand that the T-60's 6DQ6 is not operating in class C. Imagine the customer-support complaints: "I'm seeing plate current even when I'm not pressing the key -- what's going on?"
     
  7. K9UR

    K9UR Subscriber QRZ Page

    Ya, not only that but the fix is something the average novice could easily handle. Looks like a simple "hints and kinks" circuit mod or two. Let's see !
     
  8. K9UR

    K9UR Subscriber QRZ Page


    Tune for maximum output using a watt meter and then advance the loading control a little. The need for a plate current metering seems optional, or an easy modification to monitor plate instead of output on the internal meter. I think I've seen a few mods to do this online.
     
  9. K1APJ

    K1APJ Premium Subscriber QRZ Page

    Well yes, if everything is working properly. But if you have no output for whatever reason the plate current could be 0 or it could be 500 mA and you couldn't tell the difference. Could be troublesome for the inexperienced operators for whom this rig was intended. Especially with the shorting-style key jack!
     
    N2EY and KA9P like this.
  10. K9UR

    K9UR Subscriber QRZ Page

    Those inexperience hams put on a cw novice transmitter have all since either upgraded or died...
    Those left in the market for these radios today are experienced..... or at least they've been around the block for a few decades.

    There are plenty of novice-class transmitters that have survived for the past 60 years ! My T-60 is from 1961....

    We forget in todays' modern era that these were all made to be inexpensive entry-class $50 transmitters - yet how many thousands were sold back in the hey day of the 1950-'s.... and how many hams got on the air and made QSO's despite not having that oh-so-critical plate current meter. No output? Easy...plop in another tube and try. Still no output? Follow the troubleshooting flowchart. Easy. Remember too that many an enginerd's product idea was over-ruled by marketing and production department - to make a box by following some simple instructions to get on the air for $49 or less.

    But ya.... that's half the fun of owning these things... what we can learn about how things were done back in the day (before I was born)...
     

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