[Amps] Ameritron ALS 500M

Ray, W4BYG w4byg at att.net
Sat Nov 21 15:08:26 EST 2015

I have had my ALS-500 mobile for about 3.5 years, driving it with an 
FT-100D at about 50 watts drive SSB and CW.  Basically it has served me 
well and has never shown a heat problem.

I have never tried it on AM, but I would suspect you would have to keep 
the output power somewhat below about 25% of what it is rated for (about 
125 watts or so), if you were going to try it on AM. That would likely 
require input drive around 12 watts from your exciter.

If you try it, initially be real sensitive of the heat build up while 
operating, especially if you are anticipating keying it for 10 minutes 
at at time.  Even then, I tend to think that amount of key down might 
stress the finals, so I would test it thoroughly (into a dummy load), 
with lower drive and shorter key down periods, working toward your goal, 
with low heat build up on the heatsink, before any significant 
operating.  If it gets to hot to hold and keep your hand on it, it's to hot.

Once you find a comfortable output power level and if you do not have a 
way to look at the waveform output for distortion.   I would ask for a 
number of quality checks when initially going on the air.

Be sure your antenna system either has a low SWR, or you have a good 
antenna tuner to provide a good match to your amplifier.  It won't like 
anything above a 2:1 SWR.
Ray, W4BYG

On 11/21/2015 10:55 AM, Mike Feher wrote:
> I probably should have asked these questions prior to buying one, but, one
> just arrived yesterday and it will still be helpful to get some user input.
> So, I just bought the subject amp and the matching Ameritron power supply. I
> would have preferred a tube amp, but, I am just no longer able to maneuver
> heavy items like I used to.
> So, this amp is about 3 dB less than a full KW, but should be adequate for
> my needs. I would like some observations from users regarding actual
> performance, duty cycle heat handling. For example can I use it on AM for
> about a 10 minute transmission? Would be nice but not necessary as I see
> myself using it mostly on SSB and CW.
> All feedback appreciated. Thanks & 73 - Mike
> Mike B. Feher, N4FS
> 89 Arnold Blvd.
> Howell, NJ, 07731
> 732-886-5960
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> Amps at contesting.com
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I'm no longer young enough to know everything!

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