Gary Schafer wrote:

The definition of peak envelope power (PEP) is: "The average power
contained in one RF cycle at the crest of the modulation envelope".
(note that the definition says "AVERAGE power" not RMS power) This is
from the FCC definition.


The definition used by OFCOM, the UK licensing authority, contains the
same words: "The average power ... in one RF cycle at the crest of the
modulation envelope" - but it also contains two useful loopholes.

The full wording is: "The average power supplied to the antenna by a
transmitter during one RF cycle at the crest of the modulation envelope
taken under normal operating conditions."

That means UK amateurs are explicitly permitted to allow for feedline
loss (very handy at UHF and higher) and abnormal transients aren't
counted. Given our 400W PEP output limit, we need all the concessions we
can get.


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Sun, 3 Oct 2004 09:16:53 +0100, "Ian White, G3SEK"
wrote:

The definition used by OFCOM, the UK licensing authority, contains the
same words: "The average power ... in one RF cycle at the crest of the
modulation envelope" - but it also contains two useful loopholes.

The full wording is: "The average power supplied to the antenna by a
transmitter during one RF cycle at the crest of the modulation envelope
taken under normal operating conditions."

That means UK amateurs are explicitly permitted to allow for feedline
loss (very handy at UHF and higher) and abnormal transients aren't
counted. Given our 400W PEP output limit, we need all the concessions we
can get.

Okay, gentlemen, I can see where you're coming from now.
Incidentally, the (UK) definition above could be construed to allow
for some really serious QRO if one takes "normal operating conditions"
to refer to *atmospheric* conditions rather than those of the station
set-up. When's the next sunspot minima? :-}
--

"What is now proved was once only imagin'd." - William Blake, 1793.

That means UK amateurs are explicitly permitted to allow for feedline
loss (very handy at UHF and higher) and abnormal transients aren't
counted. Given our 400W PEP output limit, we need all the concessions we
can get.

73 from Ian G3SEK
=======================================

It's also very handy on 160 meters.

For example, if the antenna is just a 15-feet length of wire and 400 watts
PEP are fed into it over 115 feet of 600-ohm single-wire transmission line,
who needs concessions?

A 15-feet length of wire, all by itself, is quite efficient on 160 meters.
Nearly all of the 400 watts fed into it will be radiated and the licensing
regulations are not violated.

Furthermore, because a transmission line of that particular length
accurately does the impedance matching, a tuner becomes redundent.
----
Reg.

"Reg Edwards" wrote in message
...

That means UK amateurs are explicitly permitted to allow for feedline
loss (very handy at UHF and higher) and abnormal transients aren't
counted. Given our 400W PEP output limit, we need all the concessions we
can get.

73 from Ian G3SEK
=======================================

It's also very handy on 160 meters.

For example, if the antenna is just a 15-feet length of wire and 400 watts
PEP are fed into it over 115 feet of 600-ohm single-wire transmission
line,
who needs concessions?

A 15-feet length of wire, all by itself, is quite efficient on 160 meters.
Nearly all of the 400 watts fed into it will be radiated and the licensing
regulations are not violated.

Furthermore, because a transmission line of that particular length
accurately does the impedance matching, a tuner becomes redundent.

=================================

But to keep things in proportion -

To radiate 400 watts from a 15-feet antenna wire, fed via a 115-feet,
600-ohm, single-wire, overhead transmission line, would require a
transmitter power of the order of 1.4 Megawatts.

So before ordering the materials to construct such an antenna and feedline
it would be better to forget all about it!

sorry smiley
----
Reg

On Sun, 3 Oct 2004 09:16:53 +0100, "Ian White, G3SEK"
wrote:

Gary Schafer wrote:

The definition of peak envelope power (PEP) is: "The average power
contained in one RF cycle at the crest of the modulation envelope".
(note that the definition says "AVERAGE power" not RMS power) This is
from the FCC definition.


The definition used by OFCOM, the UK licensing authority, contains the
same words: "The average power ... in one RF cycle at the crest of the
modulation envelope"

Hang on a minute, Ian!
I've just looked in your book and in section 6-5 you say in a passage
on Peak Envelope Power: "PEP is the RMS RF power level at the peak of
the modulating waveform." "RMS"? Which is it: RMS or AVERAGE??
Not getting confused, are you? ;-}
--

"What is now proved was once only imagin'd." - William Blake, 1793.

Paul Burridge wrote:
The definition used by OFCOM, the UK licensing authority, contains the
same words: "The average power ... in one RF cycle at the crest of the
modulation envelope"

Hang on a minute, Ian!
I've just looked in your book and in section 6-5 you say in a passage
on Peak Envelope Power: "PEP is the RMS RF power level at the peak of
the modulating waveform." "RMS"? Which is it: RMS or AVERAGE??

It's not a term I would use any more; but if the first sentence hadn't
tired you out, the rest of that sidebar would have told you exactly what
I meant by it.

Not getting confused, are you? ;-}

No, just getting more careful about writing things that can be
selectively misquoted :-(


--
73 from Ian G3SEK 'In Practice' columnist for RadCom (RSGB)
http://www.ifwtech.co.uk/g3sek

On Sun, 3 Oct 2004 09:16:53 +0100, "Ian White, G3SEK"
wrote:


|
|That means UK amateurs are explicitly permitted to allow for feedline
|loss (very handy at UHF and higher) and abnormal transients aren't
|counted. Given our 400W PEP output limit, we need all the concessions we
|can get.


When our FCC changed the power limit from DC input to rf output I
assumed that the feedline was part of a "distributed" amplifier output
matching network and moved my Bird sensor to the antenna feedpoint.

Feedline loss? What feedline loss? [g]