Marv says:
>but isn't using a two-tone test signal and a Bird (or whatever
wattmeter is >handy), whence the indicated power is equal to 1/2 the peak
power, still a >valid method for measuring SSB Peak Envelope Power?
No. If you put on tone 1 only, measure power, put on tone 2 only, set to
same power, you can then apply both tones for a PEP of 4 times the power of
the individual tone. Possibly with the peak reading circuit in the Bird, you
could multiply by 2, but I don't know enough about that bit of gubbins. If
the meter/detector is the normal average reading type of a directional
wattmeter, the reading should be multiplied 2(2/pi)^2, or 2.45 to get PEP
from a 2 tone.
A thermo ammeter approach could be used: the accuracy of thermo-ammeters is
probably worse than oscilloscopes! Thermo ammeters need to be calibrated at
the frequency of use, as I found out, unless you're sure that the heating
element is non-magnetic. If it is magnetic, its resistance increases with
frequency (skin effect) so the reading goes up with frequency. Added to
that, most thermo ammeters I've seen recently have been between 25 and 60
years old.
Of course, it depends what you're trying to do - just stay reasonably within
the law (where I guess most administrations won't argue if you're 10 or even
20% out), paralyse the neighbourhood by running grossly excessive power, or
trying to beat NIST for accuracy!
73
Peter G3RZP
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