>
>
>Hi All,
>
>If I may, I'd like to start a "philosophical" thread which arises from:
>i) many of us home-brewing amps
>ii) tuning with a string of high-speed (i.e. high-speed
> compared to the time constants of our meters) vs.
> key-down, vs. whistling or saying "hoooooooola" into
> the microphone.
>iii) our desire to remain legal.
>
? FCC inspectors allow 10% for error, so the actual limit is 1650w.
However, I know of instances where the 1650w figure was slightly exceeded
without raising inspectors' eyebrows. The bottom-line is that even
1db/26% makes virtually no difference on the air, so who really cares?
FCC inspectors are more likely to be after sources of interference than
gnats. .
>Here's the situation: (non-US hams, please fill in the appropriate
>numbers)
>
>Suppose I tune my home-brew amp to put out the US allowed
>maximum of 1500W under key-down conditions. My HV drops from say
>3200V (key up) to 3000V (key down). Now if I send CW, my HV doesn't
>drop quite as far, so I'm probably putting out more power, say 1600W
>for the sake of the example. If I transmit SSB, the HV dops even
>less, and I'll actually be putting out maybe 1700W PEP.
>
>Now if I'm able to monitor my output signal with a good oscilloscope,
>(and my antenna represents a pure resistive load whose value I know
>accurately, but let's not go there right now) then I can just turn
>down my drive a bit, and stay legal. The burden of staying below
>1500W PEP output power is on me, the designer, builder,
>owner-operator of the amp. But suppose I don't have a sure-fire, lab
>quality means of measuring my true PEP under all conditions (FM, CW,
>SSB, AM etc.) How can I be sure I get maximum output and still
>comply? Well, I can tune with a string of fast dits. But the
>problem (of exceeding 1500W PEP) still remains; it's just different
>in magnitude.
>
>But wait! It doesn't have to be a HB amp! What if I own one of many
>1500W output commercially available, type-approved, amplifiers? I
>still have the same problem(s)! How does, say, Alpha Power, (to take
>a high-quality example) make sure that no more than 1500W goes out?
>Did they have to do that to get US FCC type acceptance? How much
>"overhead," i.e. how much more than 1500W PEP does the FCC consider
>compliant? Are high speed dits satisfactory? Do the manuals include
>this as a tuning method? Should they?
>
>These questions came to me in an RF-induced dream after a recent
>contest. Maybe I should post this to an FCC part97 reflector! 8>)
>All responses are welcome!
>
>73,
>
>George T. Daughters, K6GT
>
>--
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>
>
- Rich..., 805.386.3734, www.vcnet.com/measures.
--
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