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Discussion in 'Amateur Radio Amplifiers' started by YO2LTC, Apr 9, 2021.

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  1. YO2LTC

    YO2LTC Ham Member QRZ Page

    Hi everybody
    I'm looking for any info (user manual, specs...) regarding:
    Thank you!

    Attached Files:

  2. N7EKU

    N7EKU Ham Member QRZ Page

  3. YO2LTC

    YO2LTC Ham Member QRZ Page

  4. N7EKU

    N7EKU Ham Member QRZ Page

    Hi Tomo,

    Not sure these even came with a manual. If it did, all it would contain was how to hook the power up, and that turning on the receive pre-amp would boost receive signal (including noise), and that you can select AM or SSB with the mode switch, and changing the power level switch changes the power level. These are CB amps made in the thousands all based on the same design. For example, here is a quote from the owner of a Texas Star DX 250 amp:

    the dx250 owners manual basically says:
    use #10 or larger wire & hookup direct to battery,for AM-
    BOTH orange & yellow buttons IN gives LOWEST output
    yellow ONLY IN is next higher level
    orange ONLY IN is 3rd highest level
    BOTH orange & yellow OUT is HIGHEST power
    for SSB, use ONLY with yellow button IN
    white button IN turns rcv preamp ON, & it works with xmit amp off
    meter is 'relative output' only-so check your 4 stages on a watmeter, see where they read on texas star meter, & use it as a guide.
    class AB1, 3.8-30mhz, 10db preamp, 13.6volts @ 20 amps, AM/FM/SSB operation, 4 watt maximum input, 2-2sc2290 transistors, 175-300 watts pep output.
    their owners manual is just a sheet of paper! now, as with almost ALL amps, their wattage ratings are a bit optimistic, w/3-4 dk & 8-9 swing you should get 80-90 dead key and about 150 swing on AM and about 150 on SSB with 12-15 watts from the radio.​

    This is the only web page I could find about it (very simple info): Accessories/Power Amplifiers/Solid State/Solid State_SL250DX.htm

    What people mean by "CB amp" is that it is an amp designed to be driven by a 4W AM or 10W SSB CB. The are usually made with no output filtering, or at a minimum, just a 30MHz low pass filter. The can be easily overdriven as CB operators like to see the power level meter "swing" up high, and maybe don't mind when the amp distorts and compresses their signal.

    For use as an amateur radio amp, low pass filtering for each band of operation would need to be added, and the biasing of the transistors would need to be checked with at least a 2-tone test to determine that it operating in a linear manner at the power setting and drive level chosen. And usually it is best to open the case up, find out what transistors it is using, then look up the transistor datasheets to determine what they are truly capable of.

    73, Mark.
    YO2LTC likes this.
  5. YO2LTC

    YO2LTC Ham Member QRZ Page

    Thanx for info
    I got it from a Garrage Sale-ish here, for a couple of beers :))
    I said to myself it will be worth trying to hook it up to my underused FT-817 but when I wanted to gather info about it...surprise! None. :)))
    As amplifiers are kinda expensive and my WAF is so low :)) I suppose I will use it as a press-paper :)) after I'll give a try to see how's cooking.

    Many thanx
    73, Tomo
  6. YO2LTC

    YO2LTC Ham Member QRZ Page

    I added the pictures...

    Attached Files:

    Last edited: Apr 15, 2021
  7. YO2LTC

    YO2LTC Ham Member QRZ Page

    Here's MRF454 Datasheet

    Attached Files:

  8. WA4SIX

    WA4SIX Ham Member QRZ Page

    That unit is Class C. Only really good for FM. SSB will be a mess with it. LPFs may bring it to legal tolerances, but better till would be to copy the bias circuit from the data sheet.

    YO2LTC likes this.
  9. YO2LTC

    YO2LTC Ham Member QRZ Page

    Thank you Ed
    How good do you think it would be for, let's say CB FM? It has a MODE switch on the front panel AM<>SSB.
    I have a friend that is trying to convince me to sell it to him. He uses CB only, no HAM license.
    Last edited: Apr 15, 2021
  10. PA5COR

    PA5COR Ham Member QRZ Page

    Looking at the tracking diode over one of the transistors it can be AB1 or a copy out of the Motorola handbook i have a copy off for a 140 watt class AB1 amplifier.

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