[TowerTalk] 4 square for 80

[jimlux]

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 at 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 at earthlink.net
>>> <mailto:jimlux at 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 at audiosystemsgroup.com <mailto:jim at 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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>>>
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>>>
>>