Bauer Power On

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

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  1. N2DTS

    N2DTS Ham Member QRZ Page

    Yea, progress!

    The load of some tubes changes between spot, tune and operate.
    That is normal.

    If I set my 813 rig up for 32ma grid drive (no B+) then in transmit its often 25 or so ma.
    Its best to have PLENTY of grid drive ability.
    I have an exciter that has a 6146 at 600 volts or more and it will not drive three 4-400's enough for plate modulation but does ok in screen modulation.
    Its good for a pair of 4-125's.
    To drive a pair of 4-400 tubes deep into class C with a lot of grid leak bias, you want more then one 6146 will do I would think.
    Tetrodes modulate best when driven well into class C, increasing the grid leak resistor increases the bias voltage and increases the drive requirements.
    I think the 813 rig (2) takes 20 watts of drive to give 32 ma and -350 volts bias.
  2. WA1QIX

    WA1QIX Ham Member QRZ Page

    That is really great! I'm really looking forward to hearing that xmtr on the air - expecting a fairly significant signal difference, as well as a major audio difference. Nice work !
    KA4KOE and (deleted member) like this.
  3. W2VW

    W2VW XML Subscriber QRZ Page

    As a point of reference, my Junkston Killowatt takes about 12 watts drive from the exciter at 50 ohms to make 24-28 mills grid drive on the pair of 4-400s. It needs much more drive on ten meters when I send signals to nobody.

    That may be a little more than some others.
    KA4KOE likes this.
  4. KA4KOE

    KA4KOE Ham Member QRZ Page

    The 707 is meeting printed advertisement matter from the 60's with regards to power output. Other parameters within spec except grid drive borderline. The PI network up top works smoothly. The TPTG driver 6CA7 wants to oscillate a bit at the operating frequency after the B+ is removed from the finals. I was warned about this potential issue as TPTG drivers tend to want to do this. Not too bad. I'll need to address this issue. Now on to phase 2, which is route cables. Spent an hour and half cleaning up the mad science corner of the garage. I'm not comfortable with operation remotely, so I'll do operations at the TX for the time being with the Hammy HQ180A as the receiver.
  5. KA4KOE

    KA4KOE Ham Member QRZ Page

    Longer video of preliminary transmit.....
    W2VW likes this.
  6. KA4KOE

    KA4KOE Ham Member QRZ Page

    Taking a break from installing conduit sleeves for routing of RF, balanced/shielded audio, control, and metering from the TX in the two car garage directly below my shack. The RF coaxial line will be routed in a separate pathway to hopefully reduce cross-talk. I have ferrite chokes aplenty in case they are needed.
  7. N6YW

    N6YW Ham Member Volunteer Moderator QRZ Page

    This is becoming one of the first 50 page threads on the AM Forum!
    Good Job!
    KA4KOE likes this.
  8. K5UJ

    K5UJ Ham Member QRZ Page

    Phillip if you work on another rig, the cloud storage is going to run out of space.
    AC0OB likes this.
  9. KA4KOE

    KA4KOE Ham Member QRZ Page

    Not gonna happen. I have found one BC tx to be quite adequate for my needs. Plus, K4SMN would kill me while I slept.

    I am a noob to this stuff. My first transmitter project was the Valiant restoration. I skipped all the intermediate steps and went for the gusto. I now understand and appreciate the allure of large contactors operating when transmitting. Next question!!!

    I wonder if I have the PI network up top set correctly. Before I converted it, I could switch from low-high power with only minor touch ups (if any) to plate tune and antenna load (it was originally a version of a PI-L). Think I have too much L in the tank?? Q too high? Or is this just how it acts? I know one thing, all the various trip relays work correctly as I've exercised them trying to get the thing to operate consistently. Minor issue and maybe operator error.

    A tad bit of blue at the top of the LH final. But, on full strap we're seeing 1.1 KW carrier......
  10. AC0OB

    AC0OB Platinum Subscriber Platinum Subscriber QRZ Page

    Of course tweaking for different levels of PO at different power settings will change, since the output impedance of the Final stage will change with a change in Input power.

    If you can get to within 15% of advertized PO, consider it a success.

    Last edited: Feb 12, 2018

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