[Elecraft] Re: More Quests: Driving (big) linear amps with the K2?

[Mark J. Dulcey]

George, W5YR wrote:
> Brian, you raise some interesting possibilities re QRO for real . . .   <:}
> 
> I would have two concerns about the setup you describe. First to raise 5
> watts to 1300 watts requires a total power increase of just over 24 dB. FCC
> regulations say that an amplifier in the amateur service must be driven
> with no less than 50 watts and may not have over 15 dB overall gain.
> 
> Now, if the K2 drove its companion 100-watt amp which then drove the big
> final, I suppose one could say that the final is being driven to 1300 watts
> output with 100 watts input and only 11 dB gain is involved. So, probably
> no problem there.
> 
> But there is another gotcha in Part 97 concerning amplifiers and that is
> the total power produced by an amplifier at frequencies other than the
> fundamental. There is a fixed power limit of 50 milliwatts on spurious
> frequency components.
> 
> Now, comes the question: is the output of the K2 sufficiently clean such
> that it can drive the 100 watt amp for a total gain of 5 watts to 1300
> watts or 24 dB and keep the spurious components to a maximum of 50 mw or
> less?
> 
> I can't recall seeing a spurious report on the K2 lately so I just don't
> know the answer to that one. But, it might come up in the scenario you
> describe.
> 
> The Harris amplifier as briefly described would appear to violate Part 97
> if driven to a KW output with 100 mw input. That is 40 db of gain . . .

The input power and gain restrictions apply to amplifiers that are 
manufactured and sold for the amateur service. Amateurs can build 
amplifiers for their own use, or adapt amplifiers from other services, 
that don't fall under those restrictions.

The spectral purity issue, however, is a real one. Any signal put on the 
amateur bands must comply with that regulation. The spectral purity of 
the K2 may or may not be an issue, depending on how good it is, and on 
how much bandpass filtering, if any, is done by the amplifier. (Any 
reasonable amplifier will have low-pass filtering, so harmonic radiation 
shouldn't be a problem. But in-band and near-band spurs could be.)