Just checking. I'm still not sure if those gas tubes are correct, but I ordered them along with resistors in case I figure out if they are wrong. I may send mfj an email asking for the actual specs on the gas tubes they use.
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Ebay AL-811H, What Have I done?
- Thread starter 338_MtRushmore
- Start date
Are amps like puppies that follow you home? There is a local that said he'd sell his SB-220 for $550. He says it looks and functions perfectly. I'm trying hard not to spend more money, but I might just bring it home.
By all means bring it home, they make super amps when they are upgraded with modern upgraded stuff. If you are not a hammie type have the thing CB "worked over" properly and it will be a powerhouse.
I told him I was still thinking about it and weighing the cost of preventative maintenance and upgrades. He got mad and said it would last forever with the stock components. He saved me some money I guess.
I got her in all done up I think. Unfortunately I don't have a dummy load or a tuner, or a resonant antenna to give her a try. I spent my bi-weekly budget on an antenna analyzer and a used tuning pulser. Oh well I guess
Before
After
Before
After
I finally plugged her in today and I realized the Ip meter wasn't working. I cleaned the contacts in the switch and got that fixed. She tuned up ok on 10m and that made me happy. I tuned it up on 160m and got a little worried about how little response I got from the load control. Obviously it is pretty course down there, but I'm still not too sure how to tune it there. Anyways, she appears to be working... for now.
So I finally got my dummy load and actually messed with this thing tonight. After I tune for peak output, how do I know how much to load it, or do I just leave the load peaked? From my understanding loading it a little more can help reduce splatter, and is safer for the tank circuit. I am thinking just peak the load then go a little further until the output drops a needle or so just to make sure it's on the heavy side?
The "heavy" side of the peak on your Load control is the direction that causes the grid current to fall slightly. Cracking it to the "light" side of that peak will cause the grid current to rise.
All amplifiers are not built the same. The "heavy" side of the peak on the Load control may be to the left on some amplifiers, and to the right on others.
73
All amplifiers are not built the same. The "heavy" side of the peak on the Load control may be to the left on some amplifiers, and to the right on others.
73
Turning the load clockwise is heavier on this amp. The question is how much is enough, and is too heavy a bad thing? Also, on 80 and 160 the load just doesn't do a whole lot. The load is marked 0 through 10. I can got 3 numbers each side of setting listed in the manual and have a hard time detecting any changes in the meters. It is really hard to peak anything that the control is that fine.
My habit is to set the Load control for max PEP output and then check the grid current. If it's below the recommended limit, I'm done. For 'touchy' radial-beam triodes like 8874 or 3CX800, a small change in the Load control can get you a big decrease in grid current. The 811A is not so touchy in this department. Probably nothing to be gained by 'cracking' the load to one side of the max PEP position.
73
73
It is easy to peak the load on 40m or above. I wonder if its because of the pulser only driving the amp with 5 watts average. I will have to try tuning the low bands with a carrier and see if it is easier to see a peak in the load.
The whole point of the pulser is to drive the amplifier with the same peak power as your SSB voice modulation. The waveform has a low duty cycle that prevents the tubes from overheating the way they can if you use a carrier for tuneup. You'll never get it peaked for normal operating power with only a 5-Watt PEP drive signal.
Or, did you mean that the pulser shows only 5 Watts on an average-reading meter?
If you don't have a peak meter, you may be stuck with using a carrier to tune the amplifier.
And stuck with the hazard of potentially blowing it up.
The pulser is only effective when used with a true peak-reading meter. A "passive" peak meter won't respond properly to the narrow waveform from the pulser.
73
Or, did you mean that the pulser shows only 5 Watts on an average-reading meter?
If you don't have a peak meter, you may be stuck with using a carrier to tune the amplifier.
And stuck with the hazard of potentially blowing it up.
The pulser is only effective when used with a true peak-reading meter. A "passive" peak meter won't respond properly to the narrow waveform from the pulser.
73