Is it time for amplifier mfgrs to step back and "rethink"

Discussion in 'Amateur Radio Amplifiers' started by KM5FL, Sep 6, 2011.

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  1. KM5FL

    KM5FL Ham Member QRZ Page

    I've been following several threads about the tube quality in 811 and 572B powered amplifiers.. It seems that almost every failure or problem is related to tube failures. This has given those otherwise great amps, a bad rap.

    I have a bit of experience at repairing amplifiers, but I am NOT an EE, not even a reasonable facsimile.. I have an interesting question for the real amp gurus that frequent this forum.... Is it possible to design and manufacture, for the masses, a reliable, easy to tune and use, HF amplifier in the 400 - 650 watt range? The design would/should be based around a popular tube (not some of those "fad" tubes from a large European country) that is readily available such as a 4CX250.. It also has be retail priced below $1,000..

    What say you guys?? Can it be done??


    KM5FL
     
    Last edited: Sep 6, 2011
  2. K7JEM

    K7JEM Ham Member QRZ Page

    Well, really, with the new solid state devices out there, it shouldn't be a whole lot more to produce an all solid state amp that is smaller lighter, and easier to tune (just change the LPF).

    I think the days of tube type amps for near legal limit (or less) will be coming to an end. I can see someone designing a 600 watt unit that is the size of a large cereal box that would plug directly into a standard 120 outlet, and weigh maybe 15 pounds. The technology is there for that sort of thing right now. And priced at under $1000.

    Joe
     
  3. W4AFB

    W4AFB Guest

    Ive had a lot of 572B and 811 amps. With various brands of tubes. I have just not experienced this huge bad tube epidemic that fellow hams are reporting. In my opinion and i have seen it first hand with some locals, is improper tuning and drive power too high. Both big reasons for premature tube failure.
     
  4. W9GB

    W9GB Ham Member QRZ Page

    Ameritron/MFJ already makes such an amplifier (ALS-600) in this power class.

    The question is really one about NEW DESIGNS.
    TUBE versus SOLID-STATE.

    For NEW Designs:
    Ceramic Tubes (Eimac or Svetlana) OR LDMOS technology (Freescale, Toshiba, Mitsubishi, etc.)

    NOT considered - Glass RF Tubes or Bipolar technology RF Transistors.
     
  5. W0BTU

    W0BTU Ham Member QRZ Page

    Very well said. If you just use some care and common sense tuning up (such as when you switch from one band to another), most tubes last a very long time indeed.
     
  6. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    The 3-500ZG is still available at a very reasonable cost and with known quality.

    For a 1 kW or so amp, it's hard to beat.

    I wouldn't use 4CX250s for this, unless it was a VHF-UHF amp. Many reasons for that.

    811A/572B/813 etc. are kind of silly nowadays other than for experimentation and having fun. But for "reliability" and "cost vs. performance" I think they're not a great deal today.

    3-500ZGs are a lot of bang for the buck and there's no shortage of supply of very high quality tubes (yet).
     
  7. K0BG

    K0BG Platinum Subscriber Platinum Subscriber QRZ Page

    I agree Steve.

    I recently received a copy of an e-mail sent to Heathkit, asking them to consider building a legal-limit, solid state amplifier. They could easily enough, but how many amateurs would layout $6k to $8k for such a beast? Not many I'd bet.

    On the other hand, they could get back into the amp business using a pair of 3-500s. However, it would be difficult to compete with Ameritron, as the cost difference between built, and kit wouldn't be much these days.
     
  8. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    That's probably true but the amp wouldn't be very difficult to build and the builder would know a lot more about his amplifier once he's finished building it, so that might be worthwhile....
     
  9. K7JEM

    K7JEM Ham Member QRZ Page

    There are several legal limit or near legal limit SS amps being sold for less than $6K, including the highly rated HL-2.5K from THP. Most are not legal limit, but some are.

    I believe that a 500-600 watt SS amp could be build for under $1000. Ameritron has a 1200 watt amp for around $2400. It isn't the highest rated amp, but apparently does work OK. Suffers from many of the Amertron type problems of poor workmanship, and faulty power supplies. Redesigning an amp with the latest MOSFET devices should reduce costs and improve reliability.

    If I had 6K to spend on an amp, I would get the THP 1.5KW output unit, they are top of the line. As such, that would be the upper limit that anyone should spend. More realistic price range might be $3500. Right now, SS amps are approximately twice the price of similar output tube units. That will surely change in the next few years, and manufacturers know this. There are unlikely to be many new designs of tube amps in the future, and more of the SS units.

    One advantage most SS units also provide is 6M operation, which helps mitigate the higher price.

    Joe
     
  10. KM5FL

    KM5FL Ham Member QRZ Page

    Very interesting replies.. But we're not talking about solid state technology, and even if we were, the closest amp to being under $1,000 is still almost $400 OVER the target price..

    Back to "tube technology", a single tube 3-500Z HF amplifier design is way, way over our target price also.

    Adding an "assemble it your self" design is really interesting.. Someone said that the reason we see so many 811 and 572B failures is due to operator error.. Now when you add in some "assemble it yourself" factors, where do you think the Failure-rate-ometer will go??

    We're not interested in what's coming to the table way down the road a ways.. We want something that could be introduced within the next few months to one year, using what's available now..

    Personally, I don't see it happening.. It would be nice if somebody proved me wrong..

    KM5FL
     
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