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RF Amplifier Tubes- whats left & affordable for a RF Amp

Discussion in 'Amateur Radio Amplifiers' started by N8FVJ, May 4, 2019.

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  1. N8FVJ

    N8FVJ Ham Member QRZ Page

    30 years ago an array of amplifier tubes were available for reasonable cost. 3-500Z, 4-400. 3-1000Z, 572B, 3CX1500, 4CX1500, 3CX1200, 8877, 8874, etc. Some are still available, but the cost is about $1.5K for the mighty 8877 tube now. Unless you have deep pockets, you best be very careful of the RF amplifier you purchase. The tube itself can cost more than your entire radio shack. Some used RF amps do not have new replacement tubes available. I would never own such an amplifier.

    Three types of RF power tubes are still available at reasonable cost- 811A, 572B and the 3-500Z. The 811A has a small plate with no reserve capacity during tuning an amplifier. I do not recommend the 811A tube. The better tubes left for sale are 572B and 3-500Z. The 572B can be purchased for about $60-70 each and the 3-500Z for $200. Both are from China and are of reasonable quality. Early Chinese 572B were terrible, but current manufacture has seemed to resolve quality issues.

    So, if you are budget minded, I would only buy 3-500Z or 572B RF tube amplifiers. The 811A amplifier is ok with drop-in replacement 572B tubes. These amps only produce up to 800 watts PEP out.
    Two 3-500Z can approach legal limit power output and four 572B are good for about 1200 watts output with the 2200-2400 high voltage amplifiers . Four 572B in an Ameritron AL-811H will only produce 800 watts PEP out and the three tube AL-811 will make the same power with three 572B tubes due to the lower 1500 volt power supply. If you purchase older 572B amplifiers such as the Heathkit SB-200 or Yaesu FL-2100B, these amplifiers are long over due for HV capacitor replacement that is an extra cost. However, if you are handy, a new filter capacitor bank is about $30 and you will need a $30 interface keying module to handle the SB-200 160 volt keying voltage. IMO you are better off with the newer AL-811 with three 572B tubes and this amplifier has 160 meters.
     
    Last edited: May 4, 2019
    VE2GCE likes this.
  2. W1QJ

    W1QJ Ham Member QRZ Page

    So right, however if you buy a 3cx800 or an 8877 based amp and the tubes are good you can search for a good set of spares in the meantime. Eventually you will find a reasonable price on good used ones. These tubes although dear can last a very long time if used in spec. Buying new is out of the question.
     
    KU3X and K5PO like this.
  3. N8FVJ

    N8FVJ Ham Member QRZ Page

    BTW- What RF amps would I recommend?

    Top of list is an Ameritron AL80B. It will produce an easy 800 watts PEP out, has 160 meters and only uses one 3-500Z tube- $800 to $1K used. A Heathkit SB-1000 is close in design to the AL-80B and called an AL-80A. Power transformer is 3 lbs less, still heavy duty enough. Avoid the Ameritron AL-80 with poor design, inadequate tube cooling and in general a very different amp vs the AL80A & AL80B.

    If 160 meters is not needed, a used Heathkit SB-220 is a fine amplifier. Find one that has a new HV filter bank installed. I seen rebuilt SB-220s for $800. I do not care for the SB-200 with tuned input issues, look elsewhere.

    A Drake L4B is a rugged amp, but may cost more than the AL-80B and has old HV capacitors. If you can find one inexpensive and have electrical skills to replace the HV capacitor bank it is a great amplifier.

    Finally, for about $650 with new 572B tubes a used Ameritron AL-811 is a real bargain. I get 800 watts PEP out with my 572B equipped AL-811 amplifier. 600 watts CW out is reasonable with the AL811 with 572B tubes.

    Careful of used 3-500Z amps with a pair of soft tubes. Replacement tubes will cost $400.
     
    Last edited: May 4, 2019
    KU3X likes this.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The Russkie tetrodes like the 4CX800 etc. are a pretty good deal.

    I never find out if those are actually still being manufactured, or if everything being used is really new old stock made years ago; but as long as there's a lot of them available, not bad.
     
  5. G0GSR

    G0GSR Ham Member QRZ Page

    Last one I bought had a date code of 1978 but works perfectly.

    Frank
     
  6. K5PO

    K5PO XML Subscriber QRZ Page

    When considering total cost of ownership, gain, and lifespan, the 8877 is still a contender. Lots of gain and the cleanest IMD tube in common amateur use that can do full legal power.

    While the Eimac branded tube is $1500+ new, you can get used Eimac 3cx1500A7 tubes for 1/3 that.

    You can also get the Eimac YC-257 or YU209-P which are interchangeable with the 3cx1500A7/8877 and have effectively the same performance.

    And of course you can also get the Chinese made 8877 variants from usually $500-800 new.

    Any of these tubes in good condition, treated properly, can be expected to give years and likely decades of serviceable use and may well outlive the hams buying them.
     
  7. KE0ZU

    KE0ZU Ham Member QRZ Page

    Another good performer with a quad of 572s is the Dentron Clipperton "L". Had mine for 5 years now, and it still meets original specs and It just keeps on keepin on.
     
  8. KC9PFH

    KC9PFH Ham Member QRZ Page

    I like my 811H with Taylor 572B's Works well for me.
     
  9. KA9JLM

    KA9JLM Ham Member QRZ Page

    8877 Medical Pulls may be available, Some may even be new, If you can find them.

    I understand the 8877 is not being used in the new MRI machines now.

    Tubes like the 8877 do not forgive operator error very well. Do not drive while drinking. :oops:
     
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  10. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That was truly a "best buy" in 1980-ish.

    I bought one brand new back then and it was a workhorse; no tuned input, but with tube type PA transmitters, didn't care. Used it with the Drake B line (tube PA transmitter) and it just worked and worked and worked. Denny had a winner there.
     

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