[Elecraft] External AMP

[Bob McGraw K4TAX]

The only thing the SB-230 needs to switch to transmit is to ground the 
center terminal of the RCA connector on the back. Now with the K3S you 
will need to provide an Amp Interface such as the Ameritron ARB-704.   
The switching rating of the K3S Amp Key circuit is not rated for the 
voltage through the SB-230 relay.

73

Bob, K4TAX


On 12/1/2018 4:54 PM, Don Wilhelm wrote:
> Ray,
>
> That relay power is normally provided by the amplifier - you do not 
> need any voltage from the transceiver unless there is some strange and 
> unusual circuit involved.
>
> Measure the voltage at the "PTT" or "KEYIN" jack of the amplifier.  Is 
> it AC or is it DC?  If AC, it will not work with the K3S which needs 
> for the voltage to be both positive and DC.
>
> If it is DC, what is the polarity?  It must be a positive voltage.
>
> Many older tube amplifier designs depended on hard relay contacts for 
> keying that cold work with AC or DC and did not care about polarity.
> In today's solid state world, one must care about such things.
>
> On 11/30/2018 10:02 AM, Raymond wrote:
>> I am using my ancient Heathkit SB 230 (original tube) with my K3s. Is 
>> there a way to get 12 volts out of acc connector to power relay?  
>> Using K3 external plug for P3 power.
>> Ray
>> W8LYJ
>>
>> Sent from my iPhone
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