Hi Vic, Yes, right after I wrote this I thought I should have checked the
position of the capacitor relative to the indicator. Yes I am working the
unit through a atr-30 tuner. Driving the unit with 100 watts I get from 1300
to 1500 out depending on the band. I always advance the load control just
slightly higher than max output. Amp does appear to work well. Its just that
the manual suggests for 40 Meters as a example load set of 3. I end up with
max power at 1.6. I realize if the antenna vswr was 1.5-1 or a little higher
I would be advancing the load a little more. I don't think its anything
major but was just curious about what other owners are experiencing
Ken W8OB
----- Original Message -----
From: "Vic Rosenthal" <vic@rakefet.com>
To: "ken cubilo" <kce@chartermi.net>
Cc: <amps@contesting.com>
Sent: Sunday, January 25, 2004 11:32 AM
Subject: Re: [Amps] info on al-1200 amp
> ken cubilo wrote:
>
> > I just put a ameritron al-1200 on line a couple of days ago. I am
> > noticing that the suggested load capacitor settings are all much
> > lower than the manual suggested settings, for max power output. I am
> > driving the amp with about 80 watts max so I suspect this has
> > something to do with it. anybody else using one of these amps notice
> > the same thing?
>
> I presume that you are testing into a 50-ohm load, right? Notice also
> that you should always adjust the load control for a slightly heavier
> load (less capacitance) than that which produces maximum output, for
> best linearity.
>
> If you are running the amp at less than rated input, then the impedance
> presented by the tubes will be higher (same Ep, less Ip), and you would
> expect proper matching to occur with less plate-C. Maintaining overall
> resonance (since the plate L is fixed) would require slightly more
> load-C (this statement is going to provoke an argument, but I stand by
it).
>
> Of course, you said 'a lot lower', so knowing Ameritron/MFJ I would
> check the positioning of the knob on the capacitor shaft just to be sure.
>
> --
> 73,
> Vic, K2VCO
> Fresno CA
> http://www.qsl.net/k2vco
>
>
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