Michael Tope wrote:
> Steve,
>
> I was speaking of the case where I have a brick on the key (A0).
> When I measured the power factor of the amp in this mode a
> while back, it was something like 0.80. I would agree with you
> that line voltage drop would be hard to measure in intermittment
> CW or SSB service, but in A0 (brick on key), I think its pretty
> straightforward. Or am I missing something?
The high current 'gulps' I meant are the ones every line half cycle, not at
syllabic rate. The line voltage your meter measures tends to reflect a cycle
to cycle average, and doesn't indicate what happens during those few ms
whereas the psu feels the full effect.
An example (imprecise, so please don't shoot me down): If your amp is
pulling an average of, say, 10A from the line for something approaching a kW
input, the charge goes into the capacitors in a space of maybe 2ms during
the half cycle of 8.33ms. The average current during those 2ms has to be
40A, with the peak being 50, 60 or even higher. That sets the voltage drop
that the psu suffers whereas your voltmeter and lights don't react so much
to the short term disturbance.
Steve
> ----- Original Message -----
> From: "Steve Thompson" <g8gsq@ic24.net>
> To: <amps@contesting.com>
> Sent: Friday, December 03, 2004 12:17 AM
> Subject: Re: [Amps] Current draw at 110 volts for SB-200 and SB-1000
>
>
>> Michael Tope wrote:
>>> I run my Drake L-7 off a 110V drop and it seems to do fine. I get
>>> about 1200 watts output with 100 watts of drive. Checking it just
>>> now, line voltage drops from 117.7 to 111.7 VAC when I go key down
>>> with maximum exciter drive (about 100 watts). There is a small, but
>>> perceptible dimming of the lights in the shack and hallway (the
>>> circuit in the hallway drops about 1.5 VAC when I key the
>>> amplifier).
>>
>> Part of the problem is that the current the amp pulls (or tries to
>> pull) is not like a resistive load but is taken in big gulps for a
>> short period. The peak current is many (typ 5-10) times the
>> 'average' you work out from the dc input. The drop from this tends
>> not to show to its full extent on ac voltage readings and dimming
>> lights, but does hit the ht in the amp.
>>
>> Steve
>>
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