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Illegal high power HF amplifiers

Discussion in 'Amateur Radio Amplifiers' started by N8FVJ, May 20, 2019.

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  1. KB9HRS

    KB9HRS Ham Member QRZ Page

    Someone is either touchy about my mention of the ARRL, the FCC, or the new group of hams raised and still living in a mental state of "gimme and entitlements".
    Hence, they removed my post.
    That's OK...Those who read my post, and operated CB in the 60's and 70's know what the radio service was once like. And we're ALL aware of what it has become. The conversation started with regard to hams running illegal amounts of amplification. I merely stated where that mindset came from. And it's being perpetuated and expanded on by a handful who have no regard for rules and regs much less their fellow hams or the hobby itself .
    The hobby will suffer from this mindset as I stated in my censored post.
    I stand by what I say and what I know.
    Read this quickly as this will probably be deleted as well.
    AF5XF likes this.
  2. K8DO

    K8DO Ham Member QRZ Page

    No such thing as an illegal amplifier simply based on the size, weight, or power out capability. There are hams radiating illegal power levels. Apples and oranges.
    There are amps which are illegal to commercially produce and sell because they do not meet the signal purity regulations - which has nothing to do with the power level.
    My COMMERCIALLY produced amps (ten tec, pal star, commander, Henry, ) which are type certificated by the FCC for sale in the USA are surely not illegal - and each will handily exceed 1500 PEP.
    Now, a ham with an amp capable of tens of thousands of watts output may be operating it at an illegal output level.. Or may not be. That is between him and the FCC.
    What someone does outside of the ham bands is not material to us as hams.
    AF5XF likes this.
  3. AI5DH

    AI5DH Ham Member QRZ Page

    Feels like Facebook or Twitter huh?
    Last edited: Dec 24, 2020
    AF5XF, K0OKS and KQ0J like this.
  4. LU6PSG

    LU6PSG Ham Member QRZ Page

    Been there...

    A single band LDMOS amplifier for just 6m band is a very different thing: easier construction, easier to compensate for leakage and strain inductances, or even can be tuned just like a tube amp, which is even better. But broad band HF is QUITE a different story. Impossible to cover the whole HF spectrum (30MHz is almost 17 times 1.8 MHz) and expect to remain Linear AB everywhere. In fact, all of the amplifiers in the market operate saturated class AB on the lower frequencies and are pushed into class D or E above 7 MHz due to leakage inductances and strain inductances impossible to compensate. And some others (like W6PQL) operate class D current mode over the whole HF spectrum.

    Go get the best LDMOS HF broadband amp in the market (not single band) and measure IMD at full specified power over the whole HF spectrum... (not only on 3.6 or 7MHz and reducing power like most IMD test i've seen)... they all simply lack linearity, they are splatterboxes. The only way to linearize these AB linear wannabe amps is by using predistortion.

    LDMOS have such low operating impedance that are just not suitable for classic AB broadband. They sure work and generate lots of power, but lack linearity due to construction constraints. A better approach is to use them as switchers under an EER scheme like Manfred Mornhinweg is developing since a couple years ago, but this also requires complex DSP/SDR processing.

    GNUUSER QRZ Member

    even if you had an amp with excessive output power as long as you are operating within the limits of your band and license level there is nothing illegal about it.
    many amps you can build can often exceed power limitations, but as an operator its your responsibility to ensure you are not broadcasting at illegal power levels. being a ham operator we are self monitored and enforced no law agencies get involved unless infraction is reported.
    this is the problem with cb these days.
    a lot of people are using large amps and no one is policing them.
    AF5XF, K8PG and KK9W like this.
  6. W7UUU

    W7UUU Principal Moderator Lifetime Member 133 Administrator Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    Please don't make stuff up.

    As an Admin, I can see every single post including deleted posts. You have not had ONE SINGLE POST removed from this thread. I went back to Post #1 a year and a half ago, page by page, post by post, and there's not ONE SINGLE POST removed**

    Utterly not true.

    QRZ Admin

    ** [one exception: on Page 10, June of 2019, a post was removed for being blank - but it was NOT posted by YOU]
    KC2PMM, K5RX, W1TRY and 3 others like this.
  7. WA4SIX

    WA4SIX Ham Member QRZ Page

    My inten
    My intent is to use 2-1800W(65V) LDMOSs for 1500W(50V) output. There surely will not be an overdriven situation.
    By what you are stating, the LDMOS & MOS amps that are commercially built do not meet FCC specifications? Or, are these just your personal standards? I thought they underwent testing to get approved. Hence, by your statements, all of the commercially built amps are illegal, due to fraudulent measurement?
    Not trying to be argumentative, just trying to understand.


    GNUUSER QRZ Member

    most likely its a tolerance issue and safety margin.
    an overpowered amp if used correctly will not have a fluctuation of output power per say as an exact output level and will not exceed thermal specifications.
    if your modulation of signal is exceeding the safe margin of your amp the signal may not be that clean and you risk failure of your equipment.
  9. WA4SIX

    WA4SIX Ham Member QRZ Page

    I think that's why I am using 3600W worth of LDMOSs to get 1500W. I figure that I should not come even close to exceeding anything in the system, if it's all made for 3600W, well, 3000W at 50VDC.

  10. AJ4GQ

    AJ4GQ XML Subscriber QRZ Page

    This post?
    Illegal high power HF amplifiers
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