On 9/25/16 10:38 PM, Guy Olinger K2AV wrote:
Tom, W8JI, put this up in an email, simply reading part 97. Note the
term "transmitter power". Power would be measured at the output of the
final amplifying stage. A transceiver and an amp would be considered a
two part transmitter.
SO that's Tom's opinion, which I value and respect, but it's also not a
statement from the FCC. Technology advances, interpretation of
regulations changes as the technology changes. An active phased array
with multiple transmitters into a combining/distributing network doesn't
really fit the basic Part 97 model of "transmitter" to "antenna".
It's not like there's one place with a nice 50 ohm impedance to put a
Bird power meter in the line.
And even then, if you had a transmitter with a output tuning network
feeding a weird impedance antenna, measuring power could be challenging.
Or consider a system using Chierex or other clever schemes that use
multiple transmitters to improve efficiency.
If I had a 4 square, and the FCC asked about my power, I'd be
comfortable summing the powers at the 4 feed points as my answer. I
suspect that when it all gets right down to it, the FCC cares about ERP
- that's what the interference issue would be from.
I know that someone once posted the result of a call to an FCC field
office with this question, but I can't find it. I remember that the
answer was "at the transmitter." Tom's logic below seems conclusive
based on the literal wording in part 97.
------------------------------------------------
peter gerba wrote:
Where is the 1500 watts we are limited to measured from ? The output of
the Amp ?
Section 97.313b covers this. "No station may transmit with a transmitter
power exceeding 1500 watts PEP."
Transmitter power. Not common point or feedline power.
Broadcast stations are assigned an ERP power, usually limited by field
strength in a direction(s) that bothers another station(s).
That seems clear.
73 Tom
http://lists.contesting.com/pipermail/amps/1997-April/000735.html
-------------------------------------------------
73, Guy K2AV
On Sun, Sep 25, 2016 at 11:59 PM, jimlux <jimlux@earthlink.net> wrote:
On 9/25/16 5:53 PM, Guy Olinger wrote:
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.
Interesting, can you point to an opinion letter or enforcement action that
says this?
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.
On Sun, Sep 25, 2016 at 7:07 PM, jimlux <jimlux@earthlink.net
<mailto:jimlux@earthlink.net>> wrote:
On 9/25/16 12:05 PM, Guy Olinger wrote:
On Sun, Sep 25, 2016 at 12:25 PM, Jim Brown
<jim@audiosystemsgroup.com <mailto:jim@audiosystemsgroup.com>>
wrote:
On Sun,9/25/2016 6:49 AM, Steve London wrote:
What problem(s) are we attempting to solve with chokes on
the 4-square
feedlines ?
Noise.
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.
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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