SB200 on AM

Discussion in 'Amateur Radio Amplifiers' started by VE1PEW, May 27, 2012.

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  1. VE1PEW

    VE1PEW Ham Member QRZ Page

    I am wondering if it is possible to add a modification to my SB200 so it can be used on am. Has anyone done this? How much trouble would it be?

  2. AF6LJ

    AF6LJ Ham Member QRZ Page

    As far as I know you should be able to run an SB-200 on AM provided you keep the carrier power down to around 100-125W, one quarter of the amplifier's Peak output.
  3. KH6AQ

    KH6AQ Ham Member QRZ Page

    The way to run it on AM is to peak the power output using the load and tuning knobs. Set the RF drive so that the RF output is 400 watts when peaked. Now back the RF carrier down until the amp RF output is 100 watts and you're ready to go.
  4. VE1PEW

    VE1PEW Ham Member QRZ Page

    Thanks for the replies. Do I just use the CW position for the mode selector?

  5. N9ZP

    N9ZP Ham Member QRZ Page

    No run it in SSB.

    I would not go above a 100 watt carrier or (dead key) for the ex cb'er crowd. Also make sure its well ventilated.
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page


    Remember to "tune up" at FULL POWER (not at 100W output power), which is probably in the 500-600W range. THEN apply the AM signal and adjust drive to about 100W carrier power WITHOUT RETUNING. That will provide the best efficiency and linearity; however efficiency of linear amplifiers used in AM service stinks. Expect it to get hot and the tube anodes to glow red, even at 100W carrier power; but this is still a 6 dB "boost" over what a typical 100W PEP SSB rig can produce, which is usually 25W carrier power, so people will notice the difference.
  7. VE1PEW

    VE1PEW Ham Member QRZ Page

    Thanks, I will try this and see how it works.

  8. WA2CWA

    WA2CWA Ham Member QRZ Page

    I've used both of my SB-200's on AM since the 80's. One still has the same 572B's that were installed in 1969. On AM, I've driven them with my Kenwood 599D Twins, Icom IC-706 MKIIG, Icom IC-7000, Icom IC-756 PRO II, Flex SDR-1000, Flex 5000A, and even an old Lafayette HA410 on 10 meters. Generally keep the output between 100 and 125 watts. Also keep a scope in line to monitor the RF output of the linear. Both SB-200's have worked great in the AM mode and, unless you old buzzard talk on and on and on during each transmission, you shouldn't notice much plate color.

    Pete, wa2cwa
  9. WA7PRC

    WA7PRC Ham Member QRZ Page

    As with any amplifier running SSB or AM, verify proper operation (no flat-topping on peaks) using ONLY an oscilloscope. Anything else is just shooting in the dark. I prefer to not guess. A suitable 'scope will have a vertical amplifier bandwidth at least twice as high as the RF frequency you wish to monitor. And, a good scope doesn't have to cost much (under $100).
  10. KH6AQ

    KH6AQ Ham Member QRZ Page

    CW is what I would use.
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