Anyone ever use a linear amp with a full sign wave generator?

Discussion in 'Amateur Radio Amplifiers' started by KN4DQE, Jun 1, 2019.

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  1. KN4DQE

    KN4DQE Ham Member QRZ Page

    Just curious. Technically it should be possible, but I'm just wondering if anyone has done it? I would think that there may be too much in-rush current to properly work. I have an AL-80B, and it appears that it would need about 1,500 watts to power it (about 8A of current at 240 volts).
  2. W5LZ

    W5LZ Ham Member QRZ Page

    A CW transmitter is a sine wave generator at some particular frequency (variable). So the answer to this is yes.

    Guess the other part, about what it takes to 'power' an AL-80B (or A), depends on what you are talking about. Primary power limits are set by that fuse size. So, at max (never gonna happen) 8A x 240V = highest possible power requirements from the power mains. Why ain't it ever gonna happen? Because that amplifier isn't designed/built to handle it, too 'un-robust'. (Don't misunderstand, I have owned more than one of them, I like them.) If you are talking about DRIVE power required to operate that amplifier (furnished by the transmitter) then RTFM! It gives a very close approximation on drive requirements/limits.
    The third possibility is that I am misunderstanding your question completely. In that case disregard all of this.
  3. WR2E

    WR2E Ham Member QRZ Page

    I think you're asking if you can run the AL-80B from an AC power generator that produces a true SINE (not "sign") wave?

    You're not talking about feeding an RF SIGNAL GENERATOR into the RF input of the amp, is that correct?
  4. K7TRF

    K7TRF Premium Subscriber QRZ Page

    I'd be more concerned about the 125+ amps you'd have to draw from your 12V input source to the inverter(assuming it's 100% efficient, which it won't be). You might get it to work, but what's the application and what's the primary power source? A battery won't last long at that current draw and even many car alternators would be heavily taxed to support that kind of load.
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Are you talking about a gasoline/diesel/propane/LNG type motor-driven generator for portable work?

    I've used amps bigger than an AL-80B on my little Honda eu2200i portable generator, which is gasoline powered and uses a high-efficiency inverter to produce 120Vrms at up to 2200VA. Works fine, but for "contest" type work where you're transmitting half the time, it sucks up a lot more gasoline than normal and goes through a tank in a couple of hours. (With lighter loads in the "ECO" mode a tank can last 8+ hours.)

    Let us know what you really mean.
  6. AG5CK

    AG5CK Ham Member QRZ Page

    I met a cber in town that had a little sweep tube amp in his car with a power inverter. That probably doesn't count. :D

    I don't know that you would need a sine wave generator for a tube amp. As long as the frequency and voltage is stable you should be fine. If you have an issue with inrush current you could build or buy a soft start circuit to put inline with the power cord.

    My concern would be not letting the generator run out of gas and keeping the engine in good repair. If the engine started surging it could be rough on the filament.
  7. N4MTB

    N4MTB Premium Subscriber QRZ Page

    I have operated a 30L1 on a boat/generator with no problem.
  8. AC0OB

    AC0OB Subscriber QRZ Page

    If you are talking about primary AC power and not transceiver input power, then the AC primary power source for your AL-80B should be about 1.5X the total power requirement of the Amp.

    Here are the primary power specs for your AL-80B:

    Normal line current at rated CW output: 12 A at 120 Vac
    Normal line current at 1000 watt PEP output: 8 A at 120 Vac
    Power line current in standby: 1 A at 120 Vac

    So the maximum AC power input for CW is 1440 Watts.

    So your AC generator should be capable of 2200 watts. If your generator has 240Vac output use that and wire the AL-80B (See manual, Page 12 for chart and fusing) for that voltage.

    I would not use a generator-inverter system because of the hash it generates.

    BTW, its "SINE" wave:

    Aren't Technician Licensees still limited to 200 Watts PEP?

  9. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That depends on the product.

    The Honda "EU" portable generators all use onboard inverters and generate no RFI anywhere in the spectrum I could ever find. We use those for portable contest operations all the time, with sensitive receivers right next to them and the antennas directly above them...spectrum whisper-quiet other than actual signals.

    They're obviously well filtered and well shielded.

    Others may not be.
    W7CJD likes this.
  10. K7JEM

    K7JEM Ham Member QRZ Page

    No, technicians have always been allowed full power above 50MHz. Below 50MHz, they are limited to 200 watts PEP. I don't know how this factors into the thread, though.
    WA9SVD likes this.

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