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Re: LF: RE: Japan on 475 kHz.

To: [email protected]
Subject: Re: LF: RE: Japan on 475 kHz.
From: Dimitrios Tsifakis <[email protected]>
Date: Tue, 23 Dec 2014 15:46:30 +1100
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Hi Hideo san,



2014-12-23 14:25 GMT+11:00 Hideho YAMAMURA <[email protected]>:
> Hello Dimitris-san,
>
>> 1) 43 db + 10*log(PEP)
>> 2) 50 dB
> we have the same regulation (with grace period now),
> but, it seems that the ministry was afraid of the actual interference,
> hence, on site test.
>
> In my quick calculation, I assumed 0.3uV/m harmonic at AM BC receiver point,
> which is about -60dBc from AM BC carrier 250uV/m in weak areas,
> assuming S/N of about 40dB for audio output,
> and, for distance of 30m, 1pW EIRP was the limit,
> and for 10m distance 1fW EIRP was the limit,
> that are -120dBc to -150dBc relative to 1W EIRP transmit.
> I hope my calculation is wrong.

On VHF and higher frequencies, the harmonics need to be -70 dBc.
Conceivably, a 50 MHz transmitter harmonic could land on an FM BC
station's frequency so this is the same problem as when a 475khz
transmitter causes interference to a 950 kHz BC station.

-120 dBc is an extreme figure!

> Do people have measured data of the noise level at around 950kHz?
> I am to try to measure it quantitatively, hopefully during the new year 
> holiday.

I imagine the noise will be variable depending on day/night and local
interference generated from MW BC stations, NDBs etc. Where I live,
there is a nasty IMD transmitted product on 486 kHz, amplitude
modulated, which makes reception difficult on 630m. This is not
generated in my antenna or receiver, it is a transmitted signal and is
related to the two powerful stations, sharing the same antenna,  on
666 kHz and 846 kHz (2x666-846=486).

73, Dimitris VK1SV

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