[Amps] Heathkit SB-1000 On RTTY

[Rob Atkinson]

The max plate current isn't the issue.  the 400 ma spec. is what it is
and can be continuous.

The issues for 100% continuous duty cycle transmission are plate
dissipation (are you exceeding 500 watts?), cooling for the tube, and
the continuous current capability of the power supply.  As always the
grid current must be kept below 130 ma.

If the supply can deliver your 400 ma continuously and you have the
amp tuned up right (I would not push for more than around 600 w. from
a single 3-500) and you are really blasting a lot of air on the tube
(and the pins!) you should be okay near 400 ma.  I bet if your output
tank circuit is good you'll get plenty of power for a reasonable Ep of
3 KV dc @ much less, around 300 ma.  If your heathkit amp has a wimpy
p.s. and/or "quiet" cooling all bets are off.

73

Rob
K5UJ

On Mon, Sep 24, 2012 at 10:57 AM, Thomas F Giella NZ4O
<nz4o at tampabay.rr.com> wrote:
> I have a Heathkit SB-1000 amplifier with the single 3-500Z. The manual for
> the Heathkit SB-1000 says a maximum plate current of 400 mA for CW and 550
> mA on SSB.
>
> What would be a safe maximum plate current for RTTY operation, which is
> obviously 100% duty cycle like AM operation?
>
> 73 & GUD DX,
> Thomas F. Giella NZ4O
> Lakeland, FL, USA
> nz4o at tampabay.rr.com
>
> NZ4O Amateur Radio & SWL Autobiography: http://www.nz4o.com
> NZ4O MF/HF/6M Radiowave Propagation Forecast: http://www.solarcycle24.org
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