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Amplifier: Seeking Recommendations

Discussion in 'Amateur Radio Amplifiers' started by KD2NOM, Aug 19, 2017.

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  1. KA9JLM

    KA9JLM Ham Member QRZ Page

    I like half inch. 50 Caliber.

    I have used 75 ohm Cable TV Hardline and put PL-259 connectors on it. The price of free was right.

    It works great. Fooled my radio I did. :oops:
     
  2. W1VT

    W1VT Ham Member QRZ Page

    http://www.micro-coax.com/
    The most expensive coax I have ever used is UT-250, which, 20 years ago, supposedly went for $5 an inch! I put sma connectors on it and used it between my 10GHz transverter and the feed for a 2' dish.

    Zack W1VT
     
    WA7PRC, N2EY and AF6LJ like this.
  3. N3DT

    N3DT Ham Member QRZ Page

    I've been using 8X for the antenna switch to antenna feed. I haven't had any issues with it for about 5 years now 80 through 6M. The 2 antennas that use it have about 65' of it and I drive it with the 80B sometimes. The feed to the switch from the shack is about 130' of either FSJ4-50B or 9086.
     
  4. KA0KA

    KA0KA Ham Member QRZ Page

    AL-80B should have the EBS disabled so the tube runs in normal AB1 service. Other than that, a nice 10dB gain for the price tag and cheep tube is nice! Better then my $1400 rip off 8877 or custom 4cx3000 amp I am having made lol
    [​IMG]
     
  5. N8CBX

    N8CBX Ham Member QRZ Page

    ??? If any meters are placed on the front panel, two are mandatory: A dedicated Ig1 meter and a dedicated Ig2 meter. You don't need filament & screen voltage indicators.
    Jan N8CBX
     
  6. K6LPM

    K6LPM Ham Member QRZ Page

    EBS?
    What is EBS?
    ? BAND SWITCH or something perhaps?
     
  7. KA0KA

    KA0KA Ham Member QRZ Page

    Jan you are missing the bottom of my RF deck photo, had you seen it you would have seen the auto-transformers for bias, screen and filament voltage all adjustable! Very nice. If you want to see more go to my QRZ but that is not what this thread was about so I did not want to get into it here...
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    EBS = electronic bias circuit and I can't find any fault with the one in my AL-80B (although I've certainly tried).

    It responds in microseconds, and watching a scope it does not alter the leading edge waveform of a CW signal even at 40 wpm, compared with switching the amplifier to standby and watching the transmitter directly. The keyer waveform on one channel, RF output on the other channel, both displayed simultaneously, look exactly the same with the amp on or off.

    That's pretty fast.:) I actually tried to find some fault with it, as it would be easy to disable and just let the tube idle at operating bias every time the amp is keyed, but I couldn't find any reason to disable it.
     
  9. K6LPM

    K6LPM Ham Member QRZ Page

    Thanks for explaination. Is this some sort of cathode biasing configuration? I suppose if curiosity is great enough I could locate a schematic online and check it out for myself .... hmmm did I just think that out loud????? Nevermind!
     
  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Download the AL-80B manual and look at the schematics. The EBS keeps the tube in cutoff (bias) until the application of an RF signal (the amp must also be "keyed" for this) and responds to very low-level signals. The amp can be driven with 80W, but the EBS switches from cutoff to operating bias with only milliwatts applied, so it doesn't cut off the leading edge of a signal. When the applied signal drops out (between dits and dahs or between syllables on SSB) the tube switches to cutoff again. In the course of a typical transmission, this might happen hundreds or even thousands of times but it's all electronic and no moving parts are involved.

    Mine was purchased new in December 2000 so it's pushing 17 years old and the circuit has never caused a problem or failed in any way.

    I think it's a "small feature" that isn't really needed, but it does keep the shack slightly cooler.
     
    WA4SIX likes this.

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