Specifications
RE: ALC Adjustment Procedure
by N6AJR on February 8, 2005 Mail this to a friend!
Belive it or not I never use ALC. I set my amplifiers manually. I just sold my 811h, and am using a IC-2KL for most of my
stuff I run them behind the IC 756 most of the time and / or the 746 some of the time, but I usually run the 746 to the
Alpha. I ran the ts 2000 through the 811H.
On the 2 KL there is a "alc set" knob in the back of the rig and I bring up the amp till it "flat tops" where more power does
not get mor output and back it down a tad from there. I check this on all bands and adjust it for a happy medium. I can
drive the 2KL to probably 800w if I push it but I run it at 450 top 475 watts in a HOT DX battle, but most of the time and
usually only about 300 watts. I find that 2 to 3 hundred watts will get you out of the noise, and short of stacked
monobanders at legal limit, the power from 300 to 500 watts is unnoicable on the far end.
on the alpha I basically tune it the same way. when the antenna is resonant, I bring up the amp with 5 or 10 watts ( in the
cw mode on the amp)and get in the ball park, then I kick it up to about 35 watts input and check the settings, then go to
SSB and tweek it again. I make sure the meters don't read higher than the stated max for each
function, and then I back it
down a tad by lowering the input a watt or two..
This running slightly less than Max smoke will keep you amp in the linear portion of their work area, with out melting
things. Always tune the amp for max out and drop the input a tad. the amp will be resonant at max out. ( you will find that
"dip the Plate and Max the load" is also where the power out is maximum.) but check to be sure.
I had a couple of clipperton L's and when you hooked up the ALC on those you got a motorboat from them so I learned to
do it other wise. Please read you manuals and follow their instructions, but remember the difference between a couple
hundred watts and legal limit is less than an s unit. so max smoke ain't worth it.
ALC Adjustment Proce
dure
by KA3TKZ on February 8, 2005 Mail this to a friend!
Great article! This is just the info I need, I am getting an amp soon. Thank you.
Whitney
KA3TKZ
RE: ALC Adjustment Procedure
by W4VR on February 9, 2005 Mail this to a friend!
Some people are actually better off staying away from ALC unless they follow a prodedure such as the one you describe;
in fact some amplifier manufacturers (Alpha for example) recommend not using it unless you have an older exciter (Drake
line, etc). If you follow the manufacterer's recommendation with regard to drive power you should not have any problems.
Now, Solid State amplfiers are a different matter; without ALC you can really overdrive the amplifier and be broad as a
barn door. ALC between exciter and amplifier is manatory with SS amps.
ALC Adjustment Procedure
by KE4ZHN on February 9, 2005 Mail this to a friend!
Nice article. Now, if only we could get more amateurs to use less mike gain. You may have a little too much mike gain if
the crickets in your back yard at night show 1500 pep on your meter. :-)
RE: ALC Adjustment Procedure
by N0TONE on February 9, 2005 Mail this to a friend!
Like a few others, I don't use ALC. I do all my RF clipping intentionally, in the low-level stages of the radio, prior to the
SSB filter. I've modified rigs to make this happen correctly. Then, I use two log amps, sample the aamplifier's input and
output, and subtract, which gives me a sample of the garbage the amp is creating. I have a level detector - if the
"garbage" exceeds 30dB below the amplifier's output, then it ALCs.
I find that the internal ALC detector on most amplifiers is just plain wrong - it causes gain reduction AFTER the splatter
has been created.
Alan's procedure is a very good starting point, but I disagree with the notion of pushing the rig enough to create RF
compression, unless you know darned well that the circuit you're compressing is intended to do that correctly. RF
compression after the SSB filter generates splattter just like an overdriven amplifier. My mod to his procedure is to back
down gain everywhere to the point where the ALC needle on the rig NEVER makes any kind of reading.