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Elimination of 15db Gain Limit on Amateur Amplifiers

Discussion in 'Ham Radio Discussions' started by KI4AX, Aug 2, 2017.

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  1. KR2C

    KR2C Premium Subscriber QRZ Page


    I care because I had one of those guys who lived less that 1/4 mile from me. When he was on 17m-10m were completely useless. I shut my rig of to go play some guitar and guess what I heard through my guitar amp?
    I certainly do give two #$%s what CBers do.
     
    KI4AX likes this.
  2. N2RJ

    N2RJ XML Subscriber QRZ Page

    These modern amplifiers can use technologies like adaptive predistortion to achieve much cleaner IMD figures. See Anan PureSignal.

    Why is this of my concern anyway? This hobby is self-policing and you ultimately are responsible for the purity of your signal.

    You can also buy one from a dealer and have it shipped here. Even CBers can do so, even hams who are ignorant of IMD can do so. It might even be cheaper than some US dealers. My SPE 1.3K-FA was cheaper from a foreign dealer than it was from Expert Linears America.

    We are also literally the only country in the world with this asinine rule. It needs to go.

    I'm pretty sure Dave Made and Wizard Built can build amps too.
     
    NL7W, WD4IGX and K7JEM like this.
  3. KA4DPO

    KA4DPO Premium Subscriber QRZ Page

    You said yourself that most amateurs have hundred watt rigs, more than enough to drive a GG linear to full legal limit. Problem? I don't see it.

    As for Adaptive Pre Distortion, Adaptive pre distortion is something that has to be done at baseband i.e., ahead of the amplifier and is not practical ( or necessary) in an analog system. Most SDR are capable of implementing APR but keep in mind that a well designed analog system doesn't really need it. Initially pre distortion was developed to linearize amplification of wideband digital signals which contained substantial 3rd and fifth order products. Modern SDR also convert digital signals to analog prior to amplification and transmission. The converted signals are obviously derived from digital form and so, contain odd order products which are the result of converting a non linear digital signal to an analog representation. Point being, SDR need APD to really sound decent.

    The upside is that it reduces the unwanted odd ordered products by as much as 40db. There is also a downside, Adaptive Pre Distortion broadens the primary signal by one half octave, that's why it sounds like ESSB, it is.

    The truth is that there is no real technical reason to build legal limit amplifiers with gain in excess of the current restriction on manufacturers. Not because of misuse on citizens band, but because it is very easy (and less expensive) to build amplifiers with reasonable drive requirements, excellent linearity, and such amplifiers can be employed by most non technical amateurs (appliance operators) without too much risk.

    This entire thread has been about whiners whining, like pole vaulting over mouse turds. I have yet to hear a single manufacturer complain about this so called issue. Years ago I managed to work almost every country on this planet running 35 watts without too much trouble and that is why I view this thread as nothing more than whining by a bunch of noobs.
     
  4. W3WN

    W3WN Ham Member QRZ Page

    Funny thing... if you look back at the history of the request, it was a manufacturer that first petitioned the FCC to remove the 15 dB limit. I guess that doesn't count as a "complaint" then?

    IMHO, the real issue is not how much power someone needs to work other stations, how much drive an HF amplifier requires for full output power, or which operators in other services may or may not illegally use HF amplifiers -- and may or may not cause EMI & RFI.

    The real issue is that a rule was put on the books for non-technical politically-motivated reasons, a rule that has harmed the Amateur Service while ultimately having minimal impact against the real intended targets. It is a rule that today is technically obsolete, in addition to having been unnecessarily in the first place. It is long past time to remove this obsolete rule from the books.
     
    N2EY, KV6O, WD4IGX and 1 other person like this.
  5. WD4IGX

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    I get that, but most people don't have that situation. I haven't even heard of anyone being on CB at any power level in a couple of decades, aside from truckers and an occasional mention here.
     
  6. KA4DPO

    KA4DPO Premium Subscriber QRZ Page

    And just how has it harmed amateur radio since I can build an amplifier with as much gain as I can. Until about a year ago I don't recall anyone complaining. An who cares about the intended targets, I'm more in favor of cleaner signals from our own ranks.
     
  7. W0AAT

    W0AAT XML Subscriber QRZ Page


    Future of amplifiers is LDMOS, tubes are antiques and on the way out. Those LDMOS chips have huge amounts of gain, 5 watts will often drive them to 1kw!
     
    N2RJ likes this.
  8. NL7W

    NL7W Premium Subscriber QRZ Page

    This is likely the case. Though, the only reservations I have concerning solid-state devices to date are their inherent susceptibility to lightning-induced voltage transients.

    Therefore, if one is considering such an amplifier in lightning-prone areas where a nearby strike is likely, please pursue a commercial-grade grounding/bonding installation, to include known adequate insurance to cover any likely equipment damage.
     
  9. N2RJ

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    I already outlined the future with a low power exciter and external high gain amplifier. One should hope that people like you don't stick this hobby in the past.

    Surprise, another thread that mentions SDRs populated by your misinformation.

    APD is currently being incporporated in nearly all new designs for solid state amps. The amps have a feedback port to the exciter, and the exciter does the predistortion. It works and it works quite well. It can yield cleaner signals at lower cost than conventional filtering and suppression.

    Again, wrong.

    Again, the default for LDMOS is 2W in 1KW out. To make it compliant to the FCC extra parts and cost need to be added, as well as extra bulk in the exciter.

    You don't know what you're talking about. Surprise.
     
  10. N2RJ

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    I don't think most of the passive components in a tube amp can survive a lightning strike. Not to mention your exciter.
     

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