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Discussion in 'Amateur Radio Amplifiers' started by WD5JOY, Oct 21, 2012.

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  1. SM0AOM

    SM0AOM Ham Member QRZ Page

    I provide advice for building and operating MF/HF transmitter sites as a consultant.

    Naturally I want my customers to be happy, so I heed the manufacturers advice with regard to transient protection, DC grounded antennas and high-pass filters in the antenna RF paths. These precautions are quite low-cost in comparison to the cost of professional HF hardware.

    Also, the Rockwell/Collins transmitters mentioned were initially interfaced to the existing antenna farm, which was built and adjusted for the existing tubed servo-tuned transmitters. They tolerated a 2:1 SWR. No harmful effects were found from these operating conditions, expect when the protection circuits sometimes reduced the output power by about 10%.

    Not even when a transient protector overdid its role and short-circuited the RF output as a result of a lightning strike was any amplifier damaged, despite a resulting SWR of more than 30:1.

    It seems that the protection circuits in professional equipment do a better job than their amateur counterparts.

  2. KE3WD

    KE3WD Ham Member QRZ Page

    So I guess the use of a good quality HF matching unit, also more popularly called the misnomer of an Antenna Tuner, has got to be ignored in order to knock the use of solid state amplification by hams?


  3. N2EY

    N2EY Premium Subscriber QRZ Page

    This basic fact (number of hours operation per year) is what far too many hams - and others - forget when comparing amateur and commercial/military practice.

    Here's another basic fact:

    Most amateur applications do not put a value on labor, but put a very high value on capital cost. This skews what products are produced and bought. Eliminating the operator has a very high value in commercial/military applications but no value at all in most amateur applications. This applies to more than just amplifiers.

    Unlike most businesses and governments, the typical amateur cannot usually justify a larger capital investment by citing labor savings. Most hams don't think in overall-life costs, either. In fact, this is why ICAS and CCS ratings came to be - amateurs would routinely push tubes way beyond manufacturer ratings and then bad-mouth the manufacturer when they failed.

    Ultimately, economics will probably win out. IMHO, it would be great if some reputable manufacturer were to set up a plant to make high-quality 3-500Z, 572B, 6146, 8873 and similar tubes popular with hams. Problem is, such tubes would probably have to be priced so high that few hams or manufacturers would buy them.

    73 de Jim, N2EY
  4. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I think SS amps are here to stay and one day toobs will all go away; but this could take a long time, as the Chinese have become pretty good at making tubes.

    Your microwave oven uses a tube. They're all made in China, at a rate of probably 100 million a year or more, and cost about $20 to run 1100W at 2.4 GHz. No SS equivalent to that, at least not at that cost point.

    It's all simple economics.
  5. AH6OY

    AH6OY Ham Member QRZ Page

    Creature comfort wise I think a little SB200 is just right for winter. The 572B tubes when idle generate a good amount of warmth. Just cut some wedges of the sticky area of post-it notes and label them for each band for the right place for each band.

    Transistor amps are always picky. Getting one with all the cables for auto band switching setup saves some labor to get you to the being picky on swr again. Good deal for operating mobile.
  6. N2EY

    N2EY Premium Subscriber QRZ Page

    The problem is that, by all reports, the popular amateur transmitting tubes coming out of China aren't of the same quality level as the magnetrons in microwave ovens. One reason is quantity; the total world market for, say, 3-500Z tubes probably isn't even 100,000 per year - if that.

    Another reason is who the customer is. The magnetrons go into microwave ovens which are tested at the factory; if their failure rate is high the factory knows about it quick. And the customer has a lot of leverage. Not so the amateur market!

    73 de Jim, N2EY
  7. AF6LJ

    AF6LJ Ham Member QRZ Page

    I would also point out.
    Magnetrons are dead simple to build.
    It's a diode with an anode with a bunch of holes in it and a magnet around the outside.
    What can go wrong?

    A 3-500Z is a triode in a glass envelope with a grid and a filament painfully close together.
    The person loading the peaces into the jig before welding must actually give a damned about making a decent product. They also need to keep their fingers out of their lunch while assembling said tube...
    Have you seen the video of 811s made in china. It's so far from a white glove operation that I cannot see how they make any tubes that work.

    I'll be a high power solid state convert when the power FETs break the 300V barrier for drain to source voltage. But until then I see the current crop of solid state high power amplifier as only two steps away from being toys.
  8. W4PG

    W4PG Super Moderator Lifetime Member 279 Volunteer Moderator Platinum Subscriber Life Member QRZ Page

    My biggest concern with a tube amp is the HEAT! I already had to put a small window A/C unit in because all the SS stuff I have still raises the temperature in the shack during the summer to uncomfortable levels!

    I have to admit I am quick to turn on the tuner if the SWR rises up a bit, thinking it helps protect the output transistors a bit. Well, it makes me sleep better at night if nothing else . . .
  9. AF6LJ

    AF6LJ Ham Member QRZ Page

    I am just looking for 300V transistors I can do the rest.
    As for Ameritron; the market rules, which is why I build my own computers. :)
    At least I get what I want.
    NQ1B likes this.
  10. KH6AQ

    KH6AQ Ham Member QRZ Page

    The question should be:

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