Remember that the Alphas tuning is not ANTENNA TUNING but tuning its tank
circuit. There is a difference, yes??
73 Ch
________________________________
From: Amps <amps-bounces@contesting.com> on behalf of Paul Baldock
<paul@paulbaldock.com>
Sent: Sunday, December 4, 2016 10:53 PM
To: amps@contesting.com
Subject: Re: [Amps] Alpha 9500 vs. Acom 2000A questions
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@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@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
> >>
> > _______________________________________________
> > Amps mailing list
> > Amps@contesting.com
> > http://lists.contesting.com/mailman/listinfo/amps
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