Where do I find my power limit, and how is it worked out?
Your licence says what you may transmit, on which bands and how loudly. That detail does not sit in the main text. It is in Annex A of the Licence, a table attached to the conditions.
Two kinds of power
Annex A talks about two different power figures, and the exam likes to mix them up.
- DC input power (Annex A, Note 1): the total direct current power input to any device energising the aerial. It is the power going into the final stage from the supply. See DC input power.
- Peak envelope power (PEP): the average power supplied to the antenna during one radio-frequency cycle at the crest of the modulation envelope. It is the power going out. See Peak envelope power.
The 2.667 rule for SSB
For J3E (single sideband voice, covered in the next lessons), the RF output PEP under linear operation is limited to 2.667 times the DC input power.
The Annex A example reads: 150 W DC input and 400 W RF output PEP "for many bands".
The garbled bit
Annex A also seems to give a lower mean-power figure for higher bands. The text reads 2.5 Watts mean, 2.5 Kilowatts peak for those bands.
Do not memorise that line. It is not a Foundation figure.
Foundation: use 100 W PEP
Annex A's 150 W DC and 400 W PEP are not the Foundation limit. Tutorial 01 says the Foundation limit is 100 W PEP. The two sources conflict, so this course follows one ruling: for Foundation questions, the answer is 100 W PEP.
You now know
- Permitted emissions, frequency bands and power are set out in Annex A of the Licence.
- DC input power is the total DC power into any device energising the aerial; PEP is the peak power supplied to the antenna.
- For J3E, PEP is limited to 2.667 times the DC input power, so 150 W DC gives about 400 W PEP.
- For Foundation questions use 100 W PEP; Annex A's 150 W / 400 W is not the Foundation limit.