[Elecraft] K3 Drive Levels and the SPE 1.3K-FA

[Bob McGraw K4TAX]

That is correct.   The current FCC regulation requires that an amp be 
limited to 15 dB of gain.

Therefore, 900 watts out with 11 watts of drive is 19.12 dB gain.     
Even with 800 watts out and 11 watts of drive the gain would be 18.61 
dB.  Not exactly legal in the USA.   dB = 10log(p1/p2)   Thus 30 watts 
input and 900 watts output is 14.77 dB gain.  A ~3 db pad on the input 
would correct the issue and make the amp "legal" to use and import into 
the USA.   I bet someone at SPE fudged the numbers on the paperwork.

73

Bob, K4TAX



On 11/21/2019 10:32 AM, Joe Subich, W4TV wrote:
>
>
> It would be more appropriate if SPE shipped their amplifiers to
> the US with the proper (legal) attenuator in place.  That way one
> would be running the K3/K3s at 30 Watts in the first place.
>
> 73,
>
>    ... Joe, W4TV
>
> On 2019-11-21 10:42 AM, john at kk9a.com wrote:
>> I have operated RTTY with my K3S in the 11 watt range not knowing 
>> that this was bad for the LPAs. It would be nice if the Elecraft 
>> K3/K3S would allow the option to turn on the 100 watt power amp and a 
>> lower power setting.
>>
>> John KK9A
>>
>> dgb ns9i wrote:
>>
>> I run a lot of rtty and digital with my K3. I always set the amp to the
>> mid range getting 8-900w out. It takes only 8-11 w drive from the K3 to
>> accomplish that.
>>
>> Note: SPE recommends to run the amp in Mid Range for digital operation.
>> When I first got the amp I made the mistake of running it in the high
>> range and melted the copper heat sink, which was not considered a
>> warranty repair, and was an expensive lesson learned.
>>
>> Over the  course of the 3 yrs. that I've owned the amp,  I have blown 4
>> LPA's in the K3 running it at 8-11w. With latest repair the tech
>> informed me that the "LPA is not rated for continuous duty at upper
>> power levels (like the digital Modes)" They suggested running 13w vs 11w
>> so the LPA wouldn't be used. If I do that it over-drives the SPE in the
>> mid-range.
>>
>> What is my suggested recourse?
>>
>> thanks 73 Dwight NS9I
>>
>
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