Hi George -
For one, I'm glad you brought this up. My understanding is that SSB PEP is
one thing and the FCC PEP output rule is another.
Actual PEP - if I understand correctly - is the power at the highest point
(ie, the peak) of the RF envelope waveform.
For the FCC PEP rule, Part 97.3 defines PEP as "The average power supplied
to the antenna transmission line by a transmitter during one RF cycle at the
crest of the modulation envelope taken under normal operating conditions."
Again, the FCC rule says: "The average...". To me there has to be 2 or
more values in order for an average to be relevant. A point (eg., a peak)
is only 1 and if they (the writers of the rule) were in fact referring to a
peak then they would have left out the reference to average.
What exactly does the above FCC rule mean? I can't remember ever seeing it
illustrated anywhere - and - I have had varying explanations from experts of
which none made any sense. (BTW - I have no sense - so, that could be the
real problem.)
Once the above is answered then we know that we all are on the same
"wavelength" (pun intended) and may then be able to learn how to accurately
determine FCC PEP in order to be legal - and - to accurately determine REAL
PEP in order to have accurate bragging information.
In my ignorance, I have about come to believe that an ordinary PEP reading
wattmeter will give an approximately correct FCC rule PEP reading. My
cheapie PEP reading pwr meter only reads to 1,200 W and I rarely even reach
that point; so, being legal on SSB has yet to be an issue for me. I take
that back. I was an op in a multi-single station in one of the DX contests
and got to watch that big Ten-Tec pump out the rf - it had a string of
lights indicating power output. The 1500W light stayed lit a lot - it was a
fun eye-opener for me.
This is the kind of thing that one would think an extra class licensee
should, by definition, totally understand. Therefore, I find admitting to
the above a little embarrassing.
Do other countries define PEP the same way the FCC PEP rule does?
Lu K5YP
----- Original Message -----
From: George T. Daughters <gdaught6@leland.Stanford.EDU>
To: <amps@contesting.com>
Sent: Thursday, January 06, 2000 9:18 AM
Subject: [AMPS] PEP philosophy/rules
>
>
> 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.
>
> 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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>
>
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