[Elecraft] KPA500 & Drake TR7

[Martin Sole]

It's worthwhile noting that either adjusting the internal ALC to limit 
power or providing some external means to control it is really quite 
essential with some of the early solid state and certainly many of the 
hybrid radios. Most of these radios had NO proper power control in SSB. 
Whilst the carrier control can be used to control CW power, on SSB they 
typically run wide open up to where the ALC kicks in and so only mic 
gain essentially sets power. Since that is a linear control it will 
amplify louder noises up to the ALC threshold. So your voice might 
ordinarily produce a peak of 20-30 watts if you have the control set 
just so but any noise will produce substantially more.

I don't know what the KPA500 says to 100watts + at its input, hopefully 
it is quite graceful about it.

Martin, HS0ZED



On 14/01/2019 02:10, Don Wilhelm wrote:
> Marcel,
>
> About the maximum voltage, that might be in the TR7 specifications. 
> OTOH, start with the pot at a low voltage and increase it until you 
> achieve the results that you want.
>
> The K3 EXT ALC default threshold is -4.0 volts, so that may be a good 
> starting point for your experiments.
>
> 73,
> Don W3FPR
>
> On 1/13/2019 5:19 PM, Marcel Jorba via Elecraft wrote:
>>   Thanks to all of for your prompt answers
>> On CW it works great thanks to the carrier adjustment control
>>
>> On SSB: it goes to 150W out very easy
>> Yes it is just for fun.
>> The K3 is great but the TR7 is funny and special.
>>
>>
>> One last question: Someone suggested to use a 9V battery  with a pot 
>> to inject a constant negative voltage in to the TR7. But any idea 
>> about the maximum voltage?
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