Re: [Amps] Current draw at 110 volts for SB-200 and SB-1000

[R.Measures <r@somis.org>]

On Dec 2, 2004, at 5:20 PM, Martin J. Morgenbesser wrote:

> I'm thinking of acquiring an SB-200 or SB-1000.
>
> While I realize that it's preferable to power the SB-200 and SB-1000 
> amps from a 220 Volt AC line, I don't currently have 220 service in my 
> shack. What I do have is a 110 Volt 15 Amp line.

Martin -- Converting a 3-wire 15A, 120v circuit to 15A, 240v is not 
difficult if you have an unfilled circuit breaker slot available in 
your breaker box.  To do this mod, switch the mains off, change the 
3-wire 120v outlets on this circuit to 3-wire 240v outlets, wrap red 
electrical tape around the white wire to indicate that it is not a N 
wire,  connect the extant black wire and white/red wire to the L1 and 
L2 connections on the 240v outlets, wire the ground wire to N/gnd on 
the 240v outlets,  remove the single 15A CB, wrap red electrical tape 
around the white wire to indicate that it is not a N wire, and install 
a dual 15A CB.  Wire the output of the dual-CB to the black and 
white/red wires.  If you desire to have 120v outlets on the same 
circuit, connect the ground wire to both N and gnd on the 120v outlets 
and connect the L to either the black or the white/red wire.  ///  
There are a number of electrical experts who will tell you that this 
arrangement is strictly immoral, unpatriotic, against the National 
Electrical Code, that it is not safe, and that it's sinful in the eyes 
of the Almighty - - but I have been using this arrangement since 1975 
without a problem.
--  note:  this configuration will not work with 
ground-fault-interrupter circuit-breakers, but since they tend to 
interrupt in RF fields, for a Ham-shack they are not satisfactory.
> My transceiver, lights and laptop together draw maybe 5 amps from the 
> line, so I wouldn't want the amp to draw more than 7 or 8 amps.
>
> In your experience with these amps, how much RF power out can I run 
> them at while keeping the amplifier's 110 volt AC line current draw 
> below 8 amps?

It's different for different modes.
> Eventually, I'll probably install 220 service in the shack, but I want 
> to know if I can use these amps in the interim with only a 110 volt AC 
> line.
>
> Perhaps I should be looking at the Ameritron AL-811 amps which are 
> rated at 8 amps of AC line current draw for 110 volt service?

The best amplifiers for 120v operation are the old Henry Radio 
amplifiers with a resonant-choke HV power supply.  The reason for this 
is that a resonant choke PS puts about 1/10 of the peak current demand 
on the mains as an equivalent C-filter power supply.
> Your thoughts and suggestions will be greatly appreciated.
>
> 73 de W7MJM
>
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Richard L. Measures, AG6K, 805.386.3734.  www.somis.org

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