[Boatanchors] 813 grid to filament short

[Al Klase]

MODIFY THE SUBJECT LINE fer PETE SAKE!!!!!

Al Klase – N3FRQ
Jersey City, NJ
http://www.skywaves.ar88.net/

On 10/2/2015 6:43 AM, rbethman wrote:
> On 10/2/2015 5:05 AM, Sheldon Daitch wrote:
>> Bob,
>>
>> thanks. I think the ERP got tossed in perhaps in error, but in 
>> defense of ERP on the broadcast bands, FM and TV stations have, in 
>> the past, used their ERP power levels in promotion material and 
>> nothing about their true transmitter power output.
>>
>> I remember many years back WBBQ in Augusta, GA, used to claim 137,000 
>> watts - 100kW in the horizontal plane and 37kW in the vertical, as I 
>> think they had a split antenna system to cover both polarizations. 
>> This may have been before circular polarized FM antenna systems 
>> became the norm, and I believe they added the vertical polarization 
>> antenna years after they went on the air.
>>
>> I note that Terman doesn't discuss asymmetrical modulation and his 
>> discussions appear to be based on sine wave modulation characteristics.
>>
>> Yes, voice audio is very asymmetrical and negative modulation peaks 
>> and positive modulation peaks in AM can give very different peak 
>> readings.
>>
>> The AM broadcasting industry has been well aware of this for years, 
>> and Leonard Kahn was one of the first, when he manufactured, and 
>> marketed to broadcasters his Symmetra-Peak device, taking advantage 
>> of this, changing audio phase the higher of the peaks was on the 
>> positive side of modulation. Most modern audio processors designed 
>> for AM transmitters have this capability built in.
>>
>> As we know, 100% negative modulation is a hard limit - carrier 
>> cut-off, but positive modulation on the AM band is limited by either 
>> the FCC (now 125%) or the modulation capability of the transmitter 
>> and perhaps how much distortion the listener was able to tolerate.
>>
>> As for monitoring, let me ramble here and if I am wrong, please 
>> correct me. Assume a relatively accurate method of measuring 375 
>> watts output, then use a scope to look at the transmitter output when 
>> 100% modulated with a sine wave, that peak level, top to bottom of 
>> the wave form, that would be your 1500 watt PEP level, right? Any 
>> major audio greater than that peak to peak level, even on voice 
>> modulation, wouldn't that exceed the 1500 watts PEP?
>>
>> 73
>> Sheldon
> Sheldon,
>
> You have it correct! Indeed, 375Watt output, modulated with 100% sine 
> wave would show the 1500 Watt PEP.
>
> That is really where the fly gets into the ointment so to speak. 
> Neither music nor human speech is symmetrical. That is why the entire 
> discussion is really moot in terms of measuring the mystical 1500W PEP!
>
> It is just about the same as hunting a Unicorn!
>
> Regards, Bob - N0DGN
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