[Amps] Expert 1k amp

[tlthompson]

Yes they are.

On 3/7/2013 9:58 AM, Carl wrote:
> Is the ARRL still using a 6dB fudge with the way they measure IMD?
>
> Carl
> KM1H
>
> ----- Original Message ----- From: "Paul Christensen" <w9ac at arrl.net>
> To: <amps at contesting.com>
> Sent: Thursday, March 07, 2013 8:06 AM
> Subject: Re: [Amps] Expert 1k amp
>
>
>> Steve,
>>
>> I did an unscientific check with my SPE 1K.  Ripple on the RF 
>> envelope at the 1KW level is no worse than with my Alpha 77Dx and 87A 
>> at 1500W.  It's just noticeable on the scope at the maximum power 
>> level.   Yes, total drain current is about 40-42 amps.
>>
>> If the QST Product Review is any indication of the amp's IMD 
>> performance, 3rd-order 2-tone is about -40 dBc.  Not sure how well 
>> that figure holds up across a sample of units.  The IMD spectra of 
>> the 2K model appears very close.  Apart from fault detection and T/R, 
>> I've not spent much time with the rest of the schematic so it would 
>> be interesting to see how they achieve reasonably good IMD at full 
>> power that's competitive with many VT amps.
>>
>> These are not "brick-on-the-key" amps.  In the case of the 1K, the 
>> software automatically cuts back power to 50% after about 15 
>> seconds.  I don't run high duty-cycle modes like RTTY, but I think it 
>> would be a painful experience in a contest between automatic power 
>> reduction and fan noise. For me, it's a good instant-on alternative 
>> for my operating modes, but it would not be my only amp.
>>
>> Paul, W9AC
>>
>>
>> ----- Original Message ----- From: "Steve Thompson" <g8gsq72 at gmail.com>
>> To: <amps at contesting.com>
>> Sent: Thursday, March 07, 2013 3:50 AM
>> Subject: [Amps] Expert 1k amp
>>
>>
>>> Yesterday I did some minor repairs to a friend's amp - resoldering 
>>> joints on the current sensing resistor. Looking at the circuits 
>>> later I noticed that the main supply voltage is regulated by having 
>>> SCRs in place of diodes rectifying the transformer secondary and the 
>>> main smoothing capacitor is 47000uF.
>>>
>>> My friend tells me the amp runs over 40A at full tilt, which means 
>>> something like 8.5V ripple on the supply (7V at 60Hz). That strikes 
>>> me as quite high and I'd expect to see some difference in amplifier 
>>> gain/output if I was running such an amp off a regulated supply and 
>>> altered the voltage that much. Has anyone measured one? Is any 
>>> 100/120Hz audible on a carrier?
>>>
>>> Steve
>>> _______________________________________________
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>>> Amps at contesting.com
>>> http://lists.contesting.com/mailman/listinfo/amps
>>
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>
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