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FL-2100F Continued

Discussion in 'Amateur Radio Amplifiers' started by K6GB, Jul 28, 2018.

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  1. AI3V

    AI3V Ham Member QRZ Page

    Good call.

    Sometimes size matters :)

    Consider some of the advice given on this website advising to ignore anode dissapation!

    I suspect there were more ft series rigs sold to cb operators by far than hams in the USA.

    Also, consider the common practice of using some sort of hideous antenna, and "tuning" the whole affair by twisting the amplifier and atu knobs at random,

    And when things get really bad deliberately turn your tube anodes cherry red to "getter" them.

    Last edited: Aug 9, 2018
  2. G3YRO

    G3YRO Ham Member QRZ Page

    Well, other than the reasons I've suggested, I can't explain why you seem to have more failures in the USA than over here !

    At least they are proper doorknobs - unlike the cheap wire-ended caps used by Ameritron!


    I'm afraid that to me, these Amps look Homebrew compared to the engineering standard of standard of the Yaesu and Kenwood amps.

    Roger G3YRO
  3. KA9JLM

    KA9JLM Ham Member QRZ Page

    For a good stash of RF rated door knobs, Get them before you trash your old microwave oven.

    The diode is nice too.

    The transformer save is a given.
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That's an AL-811H which is pretty low powered and only operates at ~1600V B+ -- although with "good tubes" they're amazingly reliable.

    All the serious Ameritron amps (the ones that run real power) use N750 Centralab doorknob capacitors as shown below.
    Ameritron amp inside.PNG
  5. AI3V

    AI3V Ham Member QRZ Page

    Do you just make this stuff up?

    There are no doorknob capacitors in a microwave.

  6. AI3V

    AI3V Ham Member QRZ Page

    Let's not confuse a hobby accessory manufactured to the lowest possible price point, and minimum legal requirements with a "serious amp"

  7. WA7PRC

    WA7PRC Ham Member QRZ Page

    I used to think my 2x 3-500Z ham amplifier was a serious amplifier, until I worked in FM broadcast and worked on a 16 KW transmitter (with antenna gain, 100KW ERP). Then, I took a tour of US Naval Radio Station, Oso, WA (aka Jim Creek). At the time, they were running below maximum at 1296A into 0.456Ω... 766KW. :cool::D
  8. G3YRO

    G3YRO Ham Member QRZ Page

    No, an AL-811H actually runs the same power as an FL2100 !

    So surely it should have proper doorknobs ? (but unlike the FL2100 it doesn't use ANY, even for the output coupling capcitor, or RF Padders.)

    Roger G3YRO
  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    But the little Ameritron AL-80B (single tube amp), which is still towards "bottom of the line" for Ameritron, does use doorknobs: Centralab 850 series N750 ones or their HTC equivalents:

    The AL-811H runs at much lower B+ than an SB-200 or Yaesu FL-2100.
  10. K9AXN

    K9AXN Premium Subscriber QRZ Page

    There is a significant difference between the requirements for the output coupling and padders used for the high side of the tank for 80 and 40.

    The coupling caps will carry a small fraction of the AC tank current and the AC voltage swing will be again a small fraction of the B+. A high end class 2 cap e.g. the CRL 850 in the earlier photo will be just fine for coupling. Notice the coupling caps in the AL811 photo were a pair of wire connected (Maybe someone can divulge the specs or photo of the caps) which probably are type 2 caps and suitable for the application.

    Also note the CRL caps in the same photo I would guess are used for the padders on the high side of the tank. They will be N750 ppm caps that put them in the class 1 category which is a requirement for participation in a tuned circuit.

    The CRL 858 capacitors in the other photo (5KV, X5U, 1000pf) have a measured temp comp value of approximately -5000 ppm which makes them a class 2 capacitor usable for low level coupling e.g. low AC voltage swing --- moderate capacity change with voltage variation --- moderate DF: Widely used and never heard of one failing.

    Long story short, check the DF of the capacitors you use. If it is over .002 they will heat and fail. The DF is directly related to the dielectric loss and heat created.

    The N750 class 1 caps will have a df of approximately .000 something

    Regards Jim
    W1BR likes this.

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