[Amps] Alpha 9500 vs. Acom 2000A questions

[MU 4CX250B]

Very good point, Dick. The 9500 accepts 4 antennas per band segment,
but the user has to manually select the segment.
Jim w8zr

Sent from my iPhone

> On Dec 4, 2016, at 2:08 PM, Dick Green <wc1m73 at gmail.com> wrote:
>
> That's a good strategy if you only have one antenna per band, but not if, like me, you have multiple antennas and antenna combinations per band. That's why I leave AlphaMax on all the time. It's a necessity. Like you, I rarely use SSB, so maybe that's why autotune doesn't keep tuning.
>
> Ultimately, the 2000A architecture may make more sense because it allows storing tuning parameters for up to 10 antennas per band. No dynamic autotune, but it's not necessary unless you vary the power level a lot.
>
> 73, Dick WC1M
>
>> On Dec 4, 2016, at 3:59 PM, MU 4CX250B <4cx250b at miamioh.edu> 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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