Discussion in 'Amplitude Modulation' started by KA4KOE, Sep 12, 2019.

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  1. K4KYV

    K4KYV Premium Subscriber QRZ Page

    Here are some links to rebuilding the Collins-type PTO (most T-368 PTOs are not actually manufactured by Collins). The articles pertain specifically to the KWS-1 transmitter and 75A3 receiver, but these PTOs are all constructed very similarly, so this should be equally useful for the T-368 and other Collins receivers such as the 75A-4.



    K6RBK likes this.
  2. N2DTS

    N2DTS Ham Member QRZ Page

    An sdr and a big amp is also good, maybe not as boring as the dyy rig but almost.
    There are four T368's on as main rigs most nights and they seem to be holding up.
    Meanwhile, ALF's dyy rig is on its way back to the creator for repair...

    A well made home brew seems to be the best since its built for the job.
    It may have some old parts, but its not old.
    Its built to sound good.
    It can be built with protection and oversize components.
    (KG2IR and K4KYV come to mind)

    Ham gear was often marginal and built to a price point and its old, think Valiant....
    Military stuff was well built but heavy and often poor sounding, and most is old.
    Plenty of BC610's still working though, along with the T368.

    And even more amazing there are a lot of Globe Kings that still work.
    Someone has a 30K-1 for sale, a nice 300 watt rig.
    A Johnson 500 may have flaws but its a very sharp looking transmitter!
  3. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    The WRL Globe Champions are, generally, pretty fair sounding. The series ended with the 350A.

    According to Leo Meyerson (a couple of years before he died), my particular 350A is one of the very last 5 transmitters ever manufactured. There are certain weird things about the transmitter that, according to Leo, mark it as one of those units.

    Glen, K9STH
  4. N2DTS

    N2DTS Ham Member QRZ Page

    That was a REALLY compact transmitter.
    The thing I don't like about WRL stuff is all the steel which gets rusty.

    The globe chump 350 is about 1/4 the size of my homebrew rig of the same power output!
    I think power output is about the same (roughly) as a 6 foot tall 30K-1....
  5. K5UJ

    K5UJ Ham Member QRZ Page

    I don't think they put out 250 w. More like ~170 - 180 w.
  6. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    The WRL Globe Champion 300, 300A, 350, and 350A all put out somewhere between 180-watts and 200-watts maximum (running over 180-watts doesn't make any difference at the "other" end but the tubes sure know the difference).

    The AX-9909 final amplifier tubes have gotten fairly scarce and expensive. However, replacing them with 5894 tubes requires about an hour, or so, of work. The 5894 is a dual tetrode designed for VHF / UHF but putting the sections in parallel makes them virtually exactly the same as the AX-9909. The tube sockets are the same and the main difference is that the plate connection comes out the base of the AX-9909 and that connection is on the top of the 5894.

    Since the 5894 was designed for VHF / UHF, they are a little more efficient than the AX-9909 and you do get a little bit more output at the same power input. Since the 5894 was used in many commercial two-way units (Motorola, General Electric, and RCA among others), they are still very inexpensive and readily available. I still have a fair number of 5894 tubes, brand new, from my two-way radio days and I converted my Globe Champion 350A tubes to use them.

    There was an article in Electric Radio about converting the Globe Champion 300 to use the 5894. This information is exactly the same for the 300A, 350, and 350A. The only modification, to this, that I did, was to fabricate a solid bar to connect the 2-plate pins together rather than using wires and clips. A little more secure and, if physical appearance means anything, does "look" better!

    Glen, K9STH
  7. K4KYV

    K4KYV Premium Subscriber QRZ Page

    The original Globe Champion was rated at 150 watts. It used a single 812A in the final, modulated by a quad of 6L6s. I used the carcass of one to build the exciter for my first high power 304TL rig. I still have it, and now it drives a pair of 8005s. The output tube is still an 812A, running 1000 volts on the plate at about 35 mA. That tube should last a lifetime.
  8. K9STH

    K9STH Platinum Subscriber Volunteer Moderator Platinum Subscriber QRZ Page

    There was an even earlier version of the original Globe Champion that used a TZ40 for 150-watts input. The TZ40 is similar to, but not exactly the same as, the 812A.

    Leo Meyerson was famous for modifying equipment based on the cheapest similar parts that he could get at the time. As such, transmitters with the same model number can certainly be a fair amount different with the circuitry.

    Glen, K9STH

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