Guy Olinger <mailto:k2av@contesting.com>
Sunday, September 25, 2016 8:53 PM
The 1.5 kW PEP is at the amplifier output.
That has been clarified with the FCC multiple times. Tuner, feedline,
antenna system losses are your problem. You are diminished by those losses
unless you either have no losses, or run illegally.
The commercial measurement scheme does not apply to the amateur service
except for a couple bands where that particular band references effective
radiated power. 1.5 kW is not allowed on those amateur bands.
73, Guy K2AV.
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jimlux <mailto:jimlux@earthlink.net>
Sunday, September 25, 2016 7:07 PM
So measure your output power at the system interface to the
"antenna".. put 1500 watts (total) into your 4 antennas: sum the
powers at each element (including if you have phased them so you have
a negative element). That's what commercial broadcasters do, isn't it?
The regulations don't say "amplifier output", they say
"PEP (peak envelope power). 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. "
"(b) No station may transmit with a transmitter power exceeding 1.5 kW
PEP. "
If I define my "antenna transmission line" reference plane at the
antenna feed points, I think that works.
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Guy Olinger <mailto:k2av@contesting.com>
Sunday, September 25, 2016 3:05 PM
On Sun, Sep 25, 2016 at 12:25 PM, Jim Brown <jim@audiosystemsgroup.com>
Noise, yes. Gotta give you that one, but the main reason for the 4 square
was TX gain, right? You do have listening antennas for 160 and 80? So we
have to worry about *loss*. Loss eats up gain from patterns. Loss eats up
amplifier output. Your *system* gain past your transceiver is antenna gain
+ amplifier gain *** minus LOSSES ***.
Diversion of power to miscellaneous conductor paths is almost universally
lossy and never in directions and modes desired in our attempts at
directional arrays.
The common mode path on the outside of coax shields is lossy first because
it has a thick jacket which is never designed for low loss, second because
it often lays on the ground or is buried, a very lossy situation. Try your
20 meter dipole laying on the ground to check that out if you're not
convinced. And if that is not enough, coax is often taped to towers,
making
it a transformer winding to the metal of the tower, whose reradiation is
certainly not going to be useful in a 4 square.
In correspondence about FCP conversion projects, I always advise
installers
to ALSO go after all those death by a thousand paper cuts losses, because
the FCP installers are physically into a lot of the situations where
corner
cutting costs transmitted power.
The first 0.3 dB loss to your brand new 1500 watts out takes away 100
watts. The second 0.3 dB takes away 93 watts, the third 0.3 dB takes away
87 watts. A 1 dB loss drops you to 1192 watts.
So three paper-cut 0.3 dB losses effectively drop your 1500 watt Alpha
9500
to 1200 watts. If your 1500 watt amp would only put out 1200 when you got
it from the factory, you would send it back to the factory, right? No? 0.3
dB losses can't be significant.
"Oh, it's all right, it's only a dB, that's fine, I love my new amp. 1200
watts is the same as 1500 watts." <smile, smile, warm smile>.
Actually, upon careful reflection, what I think I really heard was
!@%&*@!!!!! #$@%@%!!!!! #^#$%^!!!!!. <pant> 1200 watts!!!!! <pant,
pant> Do they think I'm an idiot ???? <pant, pant, pant> <Finger nails
on chalk board type scream>.
Oh, that's better. For a moment I thought you were overdosed on Elavil.
If you see a preventable 0.3 dB loss, step on it like a roach and kill it
before it multiplies. Don't put up with any 0.3 dB loss you don't have to,
and if you do have to put up with it, know *exactly why* you have to. Then
that 4 dB you can count on actually gettting out of a 4 square for sure,
regardless, will really mean something. I have a list of nearly thirty
different ways to waste 0.3 dB of RF energy. When I get done it might be
more than thirty.
Common mode losses can be way more than 0.3 dB.
Remember.... Death by a thousand paper cuts.....
I won't go into why and when isolation transformers can be be better than
ferrite based balun and choke type windings. That's a whole other story.
I have a design for an upside down 80m 4 square for mounting around a
tower, that does not touch the ground, does not involve large RF fields in
or near the ground, and uses the top Philly-stran guys to support FCP's as
counterpoises for the upside down verticals, and deals with common mode in
a way that is definitely out of the traditional "you gotta have 1/4 wave
radials" box. But it's not ready for general publishing. Anyone interested
in trying this experimental design, email me off list.
73, and good luck on the 4 square.
Guy K2AV
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