Illegal high power HF amplifiers

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

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  1. G0GSR

    G0GSR Ham Member QRZ Page

    So what's the maximum power that anyone has reliably "heard of" being used on an Amateur band?
    I have an answer but will wait and see what others say first and NO, I'm not admitting to anything myself.

  2. W5LZ

    W5LZ Ham Member QRZ Page

    'GSR' -
    I can tell you what the max -legal- power is in this country. I can also tell you (I saw it) a friend had an amplifier that -could- (not necessarily -would-) do as much as one of the broadcast stations here in town. No idea what the tube was, but it was as large as a gallon pickle jar (the glass tube, also had a ceramic with handles). I didn't see either of them running so have to assume they were under driven all the time...
    I'm not in that 'class', my amp would barely do legal limit if I really pushed it. After buying replacement tubes once, it didn't get pushed much at all.
  3. KM1H

    KM1H Ham Member QRZ Page

    By reliably do you mean being there personally to measure? That is a bit restrictive:rolleyes:

    OTOH I have been present when 10-20KW was in use or heard it directly from the user.

    On CB I witnessed a shootout at Dayton where up to 40 KW was used and I have no doubt hams have exceeded that.

    I have also been at the US end at K0NAB NAS Olathe KS, during 20M phone patches when the Wheelus AFB end in Libya kicked in the 50KW amp to blast thru deliberate QRM. I doubt if the FCC had the gonads to complain:eek:

    K0UO likes this.
  4. KA4KOE

    KA4KOE Ham Member QRZ Page

    I remember Gator Stakes run on 3895 in the early 80's. Basically it was a high power contest with competitive heats. If you were heard in the first heat, you'd not participate in the others. The moderator would say "callsigns only for 60 seconds". There would be up to 8 heats, if memory serves. It was pandemonium but fun to listen to...just a solid wall of sound! The competition was FIERCE! I heard a rumor that someone had an amp/genset on a trailer running around 30 KW. The fellow got wind of an FCC raid and moved the trailer. The inspectors, of course, saw the ruts in the earth and asked what was parked there. The ham, of course, just shrugged his shoulders.
  5. G0GSR

    G0GSR Ham Member QRZ Page

    I used to work at a shortwave broadcast station in the late 70's.
    Back in those days, most of the engineers and Engineer in charge were Amateurs, not so now. We also had quite a young staff at this time.
    A brief QSO was made on 40m AM using 100kW during site's maintenance break when all other TX's were shut down.
    It's a shame as there were also 250kW TX's on site but the 100kW was easier to get going.

    The antenna was a HRRS4/4 curtain array with a different one for RX spaced about a mile apart but we still pulled the RX ant when on TX. RX was a GEC BRT400 which was already there.
    It was impossible to use a RX on any frequency (even TV) at the site outside the maintenance break.
    The owner of the call that was used is now SK so no comeback..

    The hardest part was connecting a mic to the TX as we needed an external mic pre-amp. TX/RX switching was impossible with such a big TX so there was some temporary wiring into the mercury arc rectifier control to quickly suppress HT during RX, otherwise there would have been a 5 sec delay going to TX.

    It WAS a short QSO and done in the interests of experimentation.... honestly!

    KW6LA, KM1H, K0UO and 1 other person like this.
  6. SM0AOM

    SM0AOM Ham Member QRZ Page

    Some memories...

    The highest power I have witnessed being used on an amateur HF band was 30 kW SSB from a Telefunken transmitter in a rhombic beamed at Bangkok.

    A former colleague at a previous employer used this power to work a quite rare Asian DX on 15 meters during the late 80s. To his dismay, he only got a 57 report...

    3o kW Telefunken ISB transmitter (early 60s)
    Commissioning measurements on a Telefunken transmitter. People from left: Bengt Dagås (SK)station manager at Grimeton long time friend and colleague, station manager Uno Nyström, SM5GA (SK) my predecessor at Swedish Telecom Radio Head Office, Erik Eriksson later station manager, and Robert Almqvist

    The 100 kW Telefunken ISB transmitter. It did however usually refuse to tune up on amateur frequencies.

    Even higher power levels had been around before my time.

    When the Thomson-CSF 500 kW AM broadcast transmitters at Hörby were commissioned during the mid-70s, the regional director present was an amateur, and tuned up on 40 meters into the giant Allgon rotatable LP antenna. If he worked anyone is not told.



    KW6LA, K0UO, AB6RF and 3 others like this.
  7. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    Beautiful pictures, Karl-Arne!

    This post got the “beer-foam out of my nose” award. :p:p
  8. W2WDX

    W2WDX Premium Subscriber QRZ Page

    You know what that tells me ... You have poor isolation on your coaxial switch to the dummy load. You were probably radiating from your antenna in reality, just a reduced signal. With some switches it could have been as much as 5-15 watts going to the antenna using an SB-200.

    But now wait ... was that 15W PEP or carrier? Hmm ... we shall never know. ;)

    As far as you "laws are made to be broken" knuckleheads, the thread is about running legally. Since it's not the gear that determines legality, it's an operational restriction. Besides that whole "... no crime committed unless you're caught" mentality is nonsense and foolhardy, not to mention patently false. Why jeopardize your freedom (or your license) following an edict by and for morons?! I guess it's fashionable to be an idiot. YEEEE HAAAAA BUBBA!!!! WE BE MORONS!!!
    Last edited: Sep 2, 2019
    K0RKH, KC2PMM, N2EY and 1 other person like this.
  9. KD2ACO

    KD2ACO Platinum Subscriber Platinum Subscriber Life Member QRZ Page

    You, sir, are babbling. The QSO distance was about 3 blocks.
    Last edited: Sep 2, 2019
    AI3V likes this.
  10. W2WDX

    W2WDX Premium Subscriber QRZ Page

    Babbling? ... I think not. Sorry, Chris. If you had isolation you should have not been radiating from a dummy load. Nor should you be able to receive for that matter, 3 blocks is far for S7. You were radiating, probably from your antenna or your lines. (Certainly not from the load itself). I bet if you hardwired the dummy load to the SB-200 you'd not see the same result.

    If you're using the Palstar tuna as the antenna/load switch, isolation issues could be even worse.

    Locally in the shack you'd hear/receive the radiation from the gear itself. But three block away ... you'd need to be radiating.

    On another note ... love the sound of the disc you sent. Beautiful cutting!!!
    Last edited: Sep 2, 2019
    N2EY likes this.

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