Bauer Power On

Discussion in 'Amplitude Modulation' started by KA4KOE, Apr 21, 2017.

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  1. K4KYV

    K4KYV Premium Subscriber QRZ Page

    I have always killed all the B+ voltages in all my transmitters during receive/stand-by. I think it's insane to do otherwise. For one thing, if they don't outright self oscillate, even the low-level stages may still generate white noise that interferes with reception. Secondly, it's too easy to forget about the voltages being on all the time and touch the wrong thing when working inside the transmitter, yet it's impossible to troubleshoot most problems with everything shut off, filaments and all. Thirdly, the unnecessary stress on components running with voltages on them (and current flowing through them) all the time inevitably shortens the life of tubes, resistors (particularly carbon), capacitors and other components.

    In the Gates, I simply added an extra DPST plate relay with contacts in series with the stock plate contactor relay contacts, one in the line to the low-voltage primary and the other to the high-voltage primary. The extra relay is energised only when the T/R switch is activated and the whole station is put in transmit mode. This relay is energised through the sequencer, the last one to come on and the first one to go off when switching from transmit to receive. What was originally the "plate on" switch on the transmitter now serves as a "ready" switch. With it "off", I can hit the station transmit switch and the exciter stages are turned on and I get grid drive, but without the HV plate supply being on. With the transmitter's "plate on" switch turned on, it goes into full transmit only when I hit the transmit switch on my station T/R relay system.

    I have heard of hams who leave their +3500 volt plate supplies on all the time, because of the difficulties of re-charging the HV filter caps each time they hit the transmit switch, but for me, no thanks. I'd install a soft-start or step-start system instead. When I'm not transmitting I want all the +HV dead.
     
  2. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Hey, let's go for 70 pages. :)

    If you don't want to deal with switching the LV you could do something clever like this:


    Phil
     

    Attached Files:

  3. KA4KOE

    KA4KOE Ham Member QRZ Page

    And I will make you proud in the long run and be forever grateful for your many kindnesses. I'm getting there.
     
  4. N2DTS

    N2DTS Ham Member QRZ Page

    I keep the bias and filaments on all the time (the rig is on) but key everything else.

    If you want quick break in ptt, you need to leave the hv on, step start is slow.
    I used to use step start but eliminated it and just use big parts and choke input that can take instant on...
     
  5. W2VW

    W2VW XML Subscriber QRZ Page

    An old timer once told me to use a sewing machine foot switch for T/R along with killing B+ on receive. The thinking was if if someone get across the B+ supply they would most likely step off the switch thus killing B+.

    I still have the same foot switch from the early 80s.

    Using RF Part's CL-80 in lieu of other step-start devices.
     
  6. K5UJ

    K5UJ Ham Member QRZ Page

    my opinion: if you use choke input filter on h.v. supply & it is at least 10 Hy then soft start not needed. Usually only 8 maybe 10 mfd filter cap is enough after the choke. The problem with thermistors is they have to cool down again before they are effective. Xmit then rx for 5 or 10 seconds then xmit again and second time the thermistor still hot and low resistance.

    HV on and rig biased off should only be used for CW. I think this idea the B+ should stay on comes from hams accustomed to leenyars.
     
  7. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    That's fine as long as know the
    time constant (the buildup of voltage) of your HV PS.

    But if it is long, you have to wait to talk in order for your HV B+ and RF to build up to a Modulate-able level.

    Below is the transient response for the 3000 HV PS in the Bauer. In essence, it is a series RLC circuit.

    I guessed a Resistance for L13 (R of L) being 120 ohms but you get the overall picture. If the (R of L) is smaller, then the voltage buildup would be quicker. Conversely, If the (R of L) is larger, then the voltage buildup would be slower.

    If you were to Key the primary of the HV PS transformer for KeyDown, it appears it would take about 2.5 to 3 seconds before you could speak.

    Addendum: I just ran another MatLab plot and for R of L being 60 ohms, and the "the-wait-to- speak" time was 2.25 seconds, so it didn't change much.


    Phil
     

    Attached Files:

    Last edited: Feb 16, 2018
  8. K5UJ

    K5UJ Ham Member QRZ Page

    Is the modulation reactor to the PA load taken into account, before modulation.
     
  9. KA4KOE

    KA4KOE Ham Member QRZ Page

    On air with good audio reports. Need to set limiter levels.
     
  10. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page


    For sure.

    Been stimulatin' (err, Simulating) that 6AG7, V2 stage and it too is screaming.

    Ole BauerMan sure enjoyed torturing tubes.


    Phil
     
    Last edited: Feb 16, 2018

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