Another AL-811 Tuning Question(s)

Discussion in 'Amateur Radio Amplifiers' started by W1DLA, Dec 17, 2010.

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  1. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    I'd keep all instructions very brief.

    PLEASE READ BEFORE OPERATING.

    "The plate TUNE and LOAD controls are adjusted to transfer maximum power into the load. The TUNE control resonates the plate tank circuit <and then annotate that with a reference to the ARRL Handbook or some easy reference> while the LOAD control optimizes the match to your antenna system.

    It is important to keep tuning sessions brief. If you cannot tune the amplifier for maximum output power consistent with minimum grid current in ten seconds or less, you're likely taking too long and could damage amplifier components.

    Two things to look at while tuning up are output power and grid current. The objective of tuning is to generate the maximum possible output power consistent with the minimum possible grid current. This may seem counterintuitive, since grid current will peak when plate current dips, and that is an indication of tuning the plate tank circuit to resonance.

    However, two things that will help keep your amplifier linear and "clean," as well as preserve the life of all components including the tube(s): These are to moderate the drive power (from your transmitter) to the amplifier, and to always MAXIMIZE the LOADing for any given drive power.

    If you have a 100W transmitter (or transceiver) you'll likely find this amplifier can be driven to full output with less than that, or about 65 Watts. As such, you always want to use "full power" (as though you will be driving the amplifier to maximum output), even if you really intend to run much less than that. The only reason to ever tune the amplifier with less than "full power" drive is if you simply don't have that available, e.g., you only have a 10W or 20W transmitter. In such case, use the full power from the transmitter you have for all tuning.

    You must use a constant carrier for tuning; this can be "CW" with the key closed, or possibly using the RTTY or FM mode selection for your transmitter. You cannot accomplish tuning while using SSB.

    Key the transmitter and amplifier (as described in the previous section) and assure the XMT indicator illuminates. Apply drive power and watch RF output and Ig (grid current). Peak the PLATE and LOAD controls for maximum output power while also monitoring Ig to assure it never exceeds xxxx mA. If you see the Ig exceeds this level, simply reduce drive power from your transmitter until Ig is below xxxx mA. Then, peak PLATE and LOAD for maximum output power.

    Once this is achieved, increase drive power from your transmitter until Ig reaches xxxx mA. Increase LOADing by turning the LOAD control clockwise (higher index number on the front panel) and you will note Ig is reduced by that adjustment.

    Re-peak PLATE tuning for maximum output power.

    The objective is to peak output power using PLATE and LOAD controls, without ever exceeding xxxx mA Ig. It is best to "practice tuning" into a dummy load rated for the amplifier's output power.

    There is no reason to "tune up" for more than about ten seconds, as this is all the time it takes to do it properly. If you see Ig exceed xxxx mA, stop transmitting and turn the drive power down. With a proper LOAD (a dummy load or well matched antenna), Ig will never exceed xxxx mA when the amplifier is tuned for maximum output power.

    After you are familiar with the tuning adjustments and their interaction, you will find simply increasing LOADing (turning the LOAD control more clockwise) can often reduce Ig to the correct level without degrading the output power. That is the proper tune point: Where you achieve the maximum possible output power consistent with the minimum possible grid current.

    Using a dummy load (preferably) try tuning up on each band. Some bands will tune very "sharply," where a very small change in tuning adjustments creates a large change in output power, while some bands will tune "broadly," where a larger change in tuning adjustments hardly impacts output power. This is the nature of multi-band amplifiers which cannot be fully optimized for any single frequency, and is not unusual.

    Now, experiment with tuning (preferably into a good dummy load rated for the amplifier's output power) and keep a written record of the results on this chart:"

    FAQs:

    -"I can't get normal output with the grid current below xxxx. What do I do?"
    A: You either have a poor load attached, or you are underloaded. If you have a reasonable load, try turning the LOAD control more clockwise while watching grid current to see if that adjustment (increasing LOADing) brings the grid current down within range. If it does, re-peak the PLATE control and watch output power and grid current to achieve full output within rated grid current. If this is not possible, call 1-800-xxx for consultation."

    ...etc.

    I'd also index every single key word in the manual:

    ALC
    AMPLIFER
    ANTENNA SYSTEM
    DUMMY LOAD
    EFFICIENCY
    GRID CURRENT
    KEYING
    LINE VOLTAGE
    LOADING
    OUTPUT POWER
    PLATE CURRENT
    PLATE LOADING
    PLATE TUNING
    POWER CONNECTIONS
    POWER OUTPUT
    TRANSFORMER TAPS
    TUNING
    VOLTAGE

    etc. Whatever there is. No excuse for any kind of manual to not be indexed, especially when this task takes maybe an hour and makes a manual far easier to use.
     
  2. KD8JDC

    KD8JDC Ham Member QRZ Page


    Good point, I agree.
     
  3. W8JI

    W8JI Ham Member QRZ Page

    I agree too, but those manuals were done when drawings were by hand and they were typed. :)

    It would be easy now with modern software to do an index, so they probably should be typed in to Word and revised.
     
  4. W8JI

    W8JI Ham Member QRZ Page

    We have found almost no one reads things like that. Customers almost all want bullets, and no more than one hundred words total if that.....and don't care HOW or why it works. That's why the AL811 manual tuning instructions are so brief, and they say the minimum necessary. I'm trying to understand what is not clear in this:

    [​IMG]

    The AL80B manual and later amps were done in modern software and are large with technical information so they should be indexed better. When the AL1200 was built, home computers were brand new. :)
     
    Last edited: Dec 20, 2010
  5. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Actually, I think that instruction from the 811 manual is very clear and really doesn't need any sort of re-write.

    I know I can download all the manuals and look at each one (and really haven't done that) but the AL-80B manual instructions are pretty lengthy, especially regarding ALC adjustment. In fact, since I've had an AL-80B for 10 years and use it quite often, I get inundated with private e-mails, probably 5-10 a week, from people asking me exactly how to set up the ALC, even after reading the manual a dozen times.

    Of course, then again, a lot of these hams (even "extras," and even some old-time hams) think the ALC controls the amplifier, and when they turn the ALC control down they are somehow magically reducing the amplifier's gain -- which of course isn't true at all. Once I explain that the ALC circuit is actually controlling their transceiver, and not the amplifier directly, sometimes a light bulb illuminates and they start to get it.
     
  6. W8JI

    W8JI Ham Member QRZ Page

    OK Steve, thanks. We found lengthy and detailed is counter productive. :)

    The index would help. I printed your suggestions and may be able to merge them into what we have. Maybe step number 10 above should have one more sentence that says "DO NOT retune or readjust at lower power except under special cases where you are instructed to do so."

    I don't like telling people what to NOT do because the list can get long. :)
     
  7. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    Sure. Actually a flow chart would probably be best for anyone who knows how to read one; a well designed "decision" chart is impossible to follow incorrectly...but some probably aren't too familiar with them.

    I recently heard from an old time ham about his AL-80B and "why doesn't the ALC control do anything?" He never connected the amp to his rig.:)
     
  8. W1QJ

    W1QJ Ham Member QRZ Page

    I will say this once again, like I did back on page 2 of this thread. I had a customer ALSO claiming there was a problem with this similar amplifier. Claimed he could not reach anywhere near maximum power output. He was confusing the RTTY load up procedure with the SSB procedure. Most hams are confused because they read elsewhere on the internet about HIGH GRID CURRENT and all the constraints put on this or that "#ma" DO NOT EXCEED!! Like I said in the earlier post, Instruction #9 says it all, drive the amp to 200MA grid or a max of 80 watts drive (whichever comes first) Adjust load and tune for maximum output, adjust drive for desired output. No additional info is given on final grid current. Usually it is more than what the MAXIMUM grid current is for RTTY. Newbies do not seem to relaize that that grid current in SSB is not as important of an issue as in RTTY. I see that was the problem with my customer and seems to be reflected over and over again with hams being overly concerned about grid current on SSB. At least this is the way I see it working out "so called" problems with customers.
     
  9. W5RKL

    W5RKL Ham Member QRZ Page

    I agree with Steve, Tom and "QJ". I mean no disrespect but it's not that the amplifier's manual is difficult to read and understand but rather operators do not seem to be able to follow simple step by step printed instructions.


    73s
    Mike
     
  10. W1DLA

    W1DLA Ham Member QRZ Page

    Well, just for comparison...and maybe it's me...but the Heathkit SB-200 manual explanation was much clearer and includes a clear sequence that is not clear to me in the Ameritron manual. As I said, I did get the help I needed...I needed help. Maybe I only have a PhD and am not qualified to read a manual with "simple step by step" printed instructions but if you do a "simple symbolic logic" diagram of the steps you will find that they are not steps at all, a comparison with the Heathkit manual will show the difference.
     
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