[Amps] Alpha 9500 vs. Acom 2000A questions

[Paul Baldock]

Autotune on the ACOM 2000A  does not vary with drive level. Autotune 
does not tune for maximum output, but it does tune for a specific 
load impedance.

For example autotune for the ACOM allows you to only use 10 to 20W 
drive. It then tunes the amplifier for a specific load impedance 
based on voltage, current and phase measurements. The ACOM 2000 tunes 
for a specific load impedance that would yield a match at 1800W 
output at the measured high voltage. Typically the output  is about 
14.5dB above the drive level, so at 10W drive during tune is 280W (not 1800W)

- Paul

At 12:59 PM 12/4/2016, you wrote:
>I don't think the autotune in the 9500 is oversensitive to impedance
>variations. It's rather that the optimal tuning point depends on the
>drive level. If you tune the 9500 with, e.g., 20 Watts of drive, it
>will tune for maximum output and efficiency at that drive. If you
>increase the drive to, say, 40W, the optimal tune and load settings
>will be substantially changed. It's normally best to autotune the amp
>for its rated output of 1500W, then turn off the autotune and save
>that setting. That way you won't be causing the autotune to hunt if
>you lower the drive power. I seldom use SSB, so don't know if the
>autotune tries to follow fluctuating voice peaks.  I hope not!
>73,
>Jim w8zr
>Sent from my iPad
>
> > On Dec 4, 2016, at 1:43 PM, Dick Green <wc1m73 at gmail.com> wrote:
> >
> > Strange that the factory recommends keeping autotune off. I've 
> never found that to be necessary with the 87A. Once it finds a 
> match, the autotune stops hunting. Could be that they're concerned 
> about antennas that are harder to match than mine, which are all 
> resonant at the operating frequency. That said, I my understanding 
> is that the 9500 autotune is considerably faster than the 87A, so 
> maybe it's more sensitive to slight impedance variations.
> >
> > 73, Dick WC1M
> >
> > 73, Dick WC1M
> >
> >> On Dec 4, 2016, at 12:48 AM, Bill Turner <dezrat at outlook.com> wrote:
> >>
> >> ------------ ORIGINAL MESSAGE ------------(may be snipped)
> >>
> >>> On Sat, 03 Dec 2016 19:08:33 -0800, Paul wrote:
> >>>
> >>> I believe the Alpha will auto tune if it wants to based
> >>> on poor SWR, but the ACOM only auto tunes when you ask it to.
> >>
> >> REPLY:
> >>
> >> The Alpha 9500 can be left in autotune mode, but the manual recommends
> >> against it because of continuous "hunting" for a match. This no doubt
> >> will cause excessive wear on the stepper motors too.
> >>
> >> Best to tune it once and shut off autotune. That's what I do and it
> >> works fine.
> >>
> >> 73, Bill W6WRT
> >>
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