MLA-2500 swamping resistor

[WA3RSL]

Hello all,

I'm building up a mini-gun station. My radio is a Elecraft KX-3 with a max output of 10 watts.

I plan to drive my MLA-2500 with it. I see in my MLA-2500 manual that the swamping resistor is 100 ohms at 25 watts.

Will I have any problems if I reduce the size of the resistor to get more output from my amp driving with a max of 10 watts?

Thanks

73

Frank

WA3RSL

[W8GP]

The swamping resistor was just a cheap and dirty way of smoothing out the input SWR without the expense and complexity of a "real" tuned input.You could add tuned input and possibly get a little more output, but I wouldn't expect more than a couple hundred watts. How much output are you getting now?

[WA3RSL]

Hello,

I don't have it hooked up yet. And I'd be happy with a couple of hundred watts out. You made me think of something else. With no tuned input, will I get a benefit of using the tuner on my KX3 while connected to my MLA-2500?

73

Frank

[W8GP]

The 8875s actually require very little drive because they have a very sensitive grid. In fact, that is the weak link of the tubes because the grid is easily damaged by excessive drive.But with only 10W, you can use the easy-drive characteristics to your advantage.The swamping resistor will potentially be dissipating up to 1/2 of your drive power so eliminating it and using a proper tuned input will definetely maximumize drive to the amp. In your case, using a tuner between rig and amp may help, especially if you eliminate the swamping resistor.But again, you'll just have to try it and see.Let me know the results of your testing.
                      Good luck, Greg

[WA3RSL]

Thanks Greg,

I'll let you know how it works when I get it going.

73

Frank

[KU7I]

I would like to hear about your test results also. Thanks. Lane Ku7i/JH1JCM US Naval Hospital Yokosuka Japan