Another AL-811 Tuning Question(s)

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

Thread Status:
Not open for further replies.
ad: L-HROutlet
ad: l-rl
ad: Left-2
ad: l-gcopper
ad: abrind-2
ad: Left-3
ad: Subscribe
ad: L-MFJ
ad: l-BCInc
  1. W1DLA

    W1DLA Ham Member QRZ Page

    So, I hear what you're saying...but, this dummy says it is marginal on 160 and the NVIS is clearly SWR prone with power increase...the dummy doesn't go sky high, just steady increase toward 2, the NVIS does go up to 6. Again, the bigger issue is why power would increase with decreasing Plate setting without any clear limit...maybe it's okay to go down but it looks like it's performing worse that way. Have an inquiry in to Ameritron.

    As for experienced hams...one of my general problems is that most folks out here are FM oriented, haven't found a good Elmer....QRZ is great for just that reason although I feel sometimes like I'm pestering folks.
     
  2. WB2WIK

    WB2WIK Platinum Subscriber Platinum Subscriber QRZ Page

    What, exactly, is your dummy load? The only thing that can make a dummy load change SWR with applied power is if it's overloaded and overheated and drifting or failed. You need a 1 kW dummy load for the amplifier, obviously. What is it that you're using?

    I haven't lived back that way in 25 years, but there "used" to be a couple of very good radio clubs in the Springfield, MA area. Hopefully, they're still around. Are you a member of any of them?

    The trick of tuning any kind of amplifier is to do it at full power and do it quickly. The AL-811 takes about five seconds to tune up from scratch. If you're exceeding that time limit regularly, you may be damaging something; and if your dummy load cannot withstand about a kilowatt, you may have damaged the load, to the extent that it now drifts with applied power, which could result in what you're describing.

    I would never start tuning an amplifier at "low power," it's just an exercise in frustration because it leads to very long tuning cycles that can be damaging. It's not "more friendly" to the amplifier to "bring it up slowly." It's much nicer to the amp to just hit it with 50-60W and tune it up at full power, quickly.

    Unfortunately one variable beyond your control or anyone's is that 811As are not such great tubes. It's a 70+ year-old design that, when made by RCA for its first 40 years, was a very good tube. RCA stopped making them 40 years ago, though, and now they're all made in China and not nearly as good as they used to be. I understand Ameritron does test every single amp with the shipping candidate tubes in it, but I'd guess that's a 60-second test and doesn't give them much exercise. Later use by owners, plus possible shock and vibration damage in shipment, can render the tubes less than ideal.

    The tube is only rated 65W anode dissipation, so three of them in parallel, if they all share power well, would be rated 195W dissipation, or about 390W output power. Most amateur designs including the Ameritron push them way beyond that, for limited duty cycle operations. But you can't "key down and keep tuning" for minutes at a time, as this is damaging. A tube that might last 30 years in SSB service might only last five minutes for tuning up, especially if a lot of that time is out of resonance.
     
  3. W1DLA

    W1DLA Ham Member QRZ Page

    The dummy is an ancient one...inherited, don't even see a brand on it just NJJ7...but, the sticker on it says it is 1KW and the SWR at 160 is 1.3-2.4, max load time 30 sec (I haven't hit it for more than 2-3) and that is about how much the SWR does range trying to tune 160.....goes from 1.3 at default values up as I drop plate, which raised power, and try to tune. That said, forget the dummy...it is spot on on other bands and I'm more concerned that trying to tune has the same problems on my well tested NVIS 160 antenna (well tested at 100W but rated for 1KW).

    I'm a member of four local clubs...I won't say more except that QRZ has been more helpful for HF, they have been great otherwise and a very good group of serious folks. A lot of interest in 10M. I have talked today with three local folks that use AL811's (but none on 160) and they are not sure what's going on on 160 here.

    Full power is pretty clearly at 35W in with this amp and this rig. It's tuning and working great (given the advice I've gotten) on all the other bands now and a number of folks have told me they do drive the AL-811 at around 35 with this rig (or something similar) and that gives them max out...that works from 80-17 for me. I have to drop down closer to 25W in from 15 meters up but am getting good power (450-500W) out and it tunes the way it should. Great signal reports, dip in plate, max power out and both plate and grid within limits. I take it down to 400W out or so to run both dropping RF in slightly and nudging Load a small bit higher (which when tuned doesn't seem to have much effect on grid current but I'm convinced to overcouple a tad).

    Again, at 160, focusing on the problem...

    35W in pins both meters regardless of settings....at 25 in, from the default start settings, the grid and plate are at about the recommended max starting out (i.e. 440ma and 150ma), power out shows about 450-500W, no SWR problem on dummy or antenna, and turning up load doesn't bring the grid current down (although it never exceeds the stated limit) it looks close to what I end up after tuning on other bands...but, the problem is, if I go to adjust the plate control from this starting point to get "max power out" (or if I drop the RF in down to start at 100ma grid as recommended and try the same) output power goes up as Plate Control goes down all the way down (grid or plate ma doesn't climb much)...but with power going above the amp rating (600W+) and, increasingly, more of it reflected with an unusable SWR.

    P.S. Put in a help ticket at Ameritron also but haven't heard back yet.
     
    Last edited: Dec 19, 2010
  4. KB0TT

    KB0TT Ham Member QRZ Page

    Learning ?

    Steve , Tom :

    It appears that this post has turned into a ' DEBATE ' . :(

    The operator has been told HOW to load that amplifier .

    Steve : You told him to load at MAXIMUM SMOKE . That is correct .

    all of this messing around with different drive levels will ' DRIVE ' him

    crazy . Tune to MAX at his operating frequency . That is IT ! ;)

    This tune-up primer is basically the same for all amplifiers .

    It is not magic . :D

    Twenty-two posts in and still not resolved . Steve , you Tom or

    myself could tune the amp ( PROPERLY ) in twenty-two seconds . :D


    He needs to find someone in his area who lnows HF AR .


    Later,



    JB


    NNNN
     
  5. W1DLA

    W1DLA Ham Member QRZ Page

    Arrogance and Hash

    I thought Ham radio was about mentoring and help.

    Indeed, the advice I got earlier was helpful in tuning up all the other bands.

    I don't know what you think MAX is but others have confirmed that it only takes 35W on my rig to max this amp and it clearly does.

    Anyway, I'm beginning to suspect it is a problem with the MFJ wattmeter/tuner at 160. Using the Bird only, and using the SWR meter in the rig, it does tune up pretty well as it should and no indication at the rig end of SWR problems. It does, however, as at upper bands, max out at around 25-30W in. It is only the MFJ tuner/meter that shows the SWR climbing.

    Anyway, get off your f_ing high horse. I've gotten a lot of help here and I appreciate those with more civility and grace.
     
  6. W8JI

    W8JI Ham Member QRZ Page

    Boy, this has spiraled downhill now.

    You know what, as the person who DESIGNED that amp and wrote the manual it is virtually impossible to walk someone through help. I asked several key questions and they were never answered.

    The most frustrating thing is without asking the operator questions so people know exactly what is going on, everyone has advice. No one can fix a problem without learning what the problem is first.

    We have him checking things that were never remotely indicated as any type of problem. Yet we don't even know if he is reading the SWR meter right or not. He has a Bird meter, that does NOT directly read SWR. He would have to use a nomograph or calculator to know SWR with the Bird, and it doesn't sound like he would know that. I don't even have any idea what MFJ meter he has, and if he knows how to read SWR on it. For all I know he is looking only at reflected power and wrongly calling it SWR.


    The dummy load obviously needs ironed out, nothing makes sense in the statement above. I have never heard of a dummy load with a 2.4:1 SWR! :)

    I honestly think the worse place in the world to learn how to do something is by asking a crowd. 15 people have 15 opinions, much of which is correct, but when it gets mixed with misinformation it all becomes a bunch of noise.

    By the time this thread goes on another day, the tubes will be melted.

    Good luck!
     
    Last edited: Dec 19, 2010
  7. KB0TT

    KB0TT Ham Member QRZ Page

    Spiral

    Tom ,

    I hope I did not cause it to spiral . Fortunately, the op is asking

    questions . Understanding the theory is a problem .

    A person does not know everything by passing the EXTRA in one day .

    My problem is that he fails to grasp what you and Steve were telling him.

    Attitude came out .

    Sorry about that .

    He will learn . I know he will .


    JB



    NNNN
     
  8. WG7X

    WG7X Platinum Subscriber Platinum Subscriber QRZ Page

    Yeah, Luck is what is needed...

    Tom, as usual is correct.

    This is a classic case of over-thinking a problem.

    Just use the better meter into the dummy load, and tune for max power without exceeding the specified max limits for plate and grid.

    It's really that simple. When the amp is tuned for max power, the various circuits are all at their resonant points. The you can lower the input power for the desired output.

    Easy as pie, once you get used to it.

    Stop worrying about turning this control or that for some supposed amp nirvana. Just tune for the max and stop.

    No other way to say it; but it is easier if someone could run you through it a time or two. If you lived in my home town I'd be glad to go over it with you but...

    73 Gary
     
  9. KI6ZIF

    KI6ZIF Ham Member QRZ Page

    Now im new to the whole amp thing. But even I have been through the Tune @ max drive thing.

    Seriously, Stop trying to tune at a reduced power out of your rig into the amp. Run your rig @ max input drive to the amp, and THEN tune. Once you have the tune set, you can reduce your rig drive. WITHOUT needing to touch the amp's settings.

    IF at that point you notice SWR problems. I would say you have some cable or antenna issues (or maybe RFI issues).
     
  10. KB0TT

    KB0TT Ham Member QRZ Page

    Hopefully

    This might be a troll thread . :mad:

    I really do not think it is one . Theory does not happen until a person

    understands basic theory . I hope he understands where we are coming

    from .

    In the Detroit area , many new EXTRA's have the attitude .

    I do not think he has that yet . Whenever I find a spike with attitude,

    it revolves around a person who passed EXTRA and always takes me to task .

    It is all good . I am never the loser . It is NOT a game .

    Hopefully, he will understand the way things work . I know he will .


    I feel sad that many new guy's develop attitudes that are caustic .

    I was just trying to buttress common practise .

    Mostly , in the past , I learned from elmers . I did NOT teach

    the ELMERS . I am not an EXTRA . I am just a stupid Advanced class

    amateur for over XXXXXXXX years . I always asked questions .

    That is how I / we learn stuff . A test with the answers never worked .


    Good Luck , :)



    JB ;)

    NNNN


    PS ZIF : Thanks for your input . Your resolve has already been addressed . Read the posts in this thread .

    TNX
     
    Last edited: Dec 19, 2010
Thread Status:
Not open for further replies.

Share This Page

ad: Alphaant-1