>Subject: Re: [AMPS] Heathkit SB-1000
>Sent: 3/28/1997 12:14 AM
>Received: 3/28/1997 2:37 AM
>From: Tom Rauch (W8JI), W8JItom@worldnet.att.net
>To: amps@contesting.com
>
>I got in a rush to reply, and started doing an AC analysis of dc tube
>currents.
>
>Tom Rauch (W8JI) wrote:
>
...snip...
>The peak instantaneous plate current in the case of the SB-1000 is actually
>about 1.4 amperes at 500 mA, so Rich wasn't far off in his estimate. He is
>incorrect
>about his saturation theory. I'm going back to bed.
good night, Tom
...snip..
When a constant-current curve bends substantively, the tube is in
downtown Saturationville. On curve #4264, any novice can see that the
1.4a and 1.6a peak-I curves have a major bend at the low end that the
1.2a curve doesn't have. However, "experts" apparently can't see this.
Also, there is nothing even close to "6 amperes" on Eimac's graph. I
don't see anything over 1.6a.
Driving a 3-500Z to more than 1.2 amps of peak anode current (400mA avg.)
is quite likely to produce a nasty signal on SSB. However, on FM or CW
it won't. If your owner's manual states that 500mA, or more, will result
in linear SSB operation, the person who wrote it *technoblathered*.
Note------- for a human voice, the plate/anode current meter indicates
about a third. If the meter indicates 130 to150 mA, the tube is actually
doing around 400mA--which you would see on an oscilloscope.
R. L. Measures,ag6k,805-386-3734
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