To: Sarvashri Sharmaji, Vijayji, Uli ji, Wolf ji and Gopalanji;
Subject: HARMFUL INTERFERENCE BY AIR ON 7066 KHZ
In these days of unfavourable propagation on most of the RF bands, and fair to good propagation on 3.5 and 7 MHz bands, the amateurs around
the whole world look to work Asian Stations with better signals.
Hence, all spurious emissions from other services, appearing in the amateur band segment 7000-7100 in Region 3 and much broader segment of 7000-7200 in some areas, and 7000-7300 kHz in the North American Area, are CAREFULLY WATCHED and logged. Hence, the reports from Germany.
We, the amateurs, do log many interesting transmissions, spurious emissions like harmonics and inter-modulation products. When the signal persists for a long time, on the amateur segment, then reporting the fact to the concerned authorities etc., starts. Many International Broadcasters like Voice of America, BBC, etc., also have such problems. They are FAST in reading our reports and taking immediate remedial measures, of course, thanking us, for our cooperation.
But, there are other stations, who trash these reports, ignoring the facts, and become noted Duds among the amateurs and short wave Listeners.
Many regional stations of All India Radio, which have simultaneous broadcastings on more than one SW frequency, ARE showing inter-modulation products, causing severe interference to amateur radio operators in the 40 metre band (7000 to 7100 kHz, soon to expand to 7200 kHz). This information has been notified to the concerned All India Radio, but, they still continue to create the inter-modulation products.
First case is from Chennai station of All India Radio. Here, the simulcast on 7160 and 7270 kHz, around 1030 UT, creating an inter-modulation spurious emission on 7050 kHz, with both the audios coming through. (2 x 7160 - 7270 = 7050 kHz)
Second case is from Mumbai station of All India Radio. Here, the simulcast on 4840 and 7195 kHz around 0230 UT creates an inter-modulation spurious emission on 7065 kHz, with both the audios coming through. (3 x 7195 - 3 x 4840 = 7065 kHz)
In another interesting case of my monitoring work at Lucknow, the AIR Domestic service transmission from Tiruchchirapalli on 936 kHz, was producing its 15th harmonic on 14040 kHz, which was the fixed frequency for all "Islands on the Air- IOTA" expeditions. I did suffer this interference, for a long time, under good propagation conditions.
There was a serious case of AIR Thiruvananthapuram, emitting many (almost five frequencies in the 40m amateur band) whenever they started their morning domestic service on 7290 kHz, from 0230 UT. The worst of the spurious emissions was on 7050 kHz where emergency communications for Tsunami etc., were carried out by amateur radio operators from India and Sri Lanka.
After continuous exchanges through telephonic conversations, E-mails, and letters, they have done something (which they are too shy to tell us), and the problem has since subsided and we are not hearing these spurious emissions in 2008 and till now in 2009.
Just out of interest, another case of harmonic emission logged at Lucknow, was from the AIR Najibabad Domestic service on 954 kHz and its 10th harmonic on 9540 kHz inside the 31 metre band, was regularly heard, with heterodyne. As this case was not inside amateur bands, this was not reported to the station, but, many SWLs enjoyed listening to the spurious transmission. [WHY NOT REPORT IT? gh]
From the capital of the country and the HQ, you are in a better position to advise your regional engineering staff, to look into these HARD CORE reports from various corners, about the spurious emissions, and take suitable action in cable layout, etc., at their transmitter sites, to stop such spurious emissions.
Good luck and all the best wishes to you all at A I R., DARC, and ARSI
Yours sincerely, from: B. L. Manohar "Arasu" VU2UR, SWL VU-0016,
VU2PE1D. Monitoring Systems Coordinator for The Amateur Radio Society
of India. MIG-6, 80 Feet Road, Kengeri Upanagara, Bangalore 560060;
Tel 080 2848 2680, Mob 09342667388
(via DJ8KR, DX LISTENING DIGEST)
DARC MONITORING SYSTEM Intruder Watch & Spectrum Control
National Coordinator: Ulrich Bihlmayer, DJ9KR, Eichhaldenstrasse 35,
72074 Tübingen, Germany Phone: .+49- 7071 - 81847 Fax: +49-7071- 82419
eMail: email@example.com [sic]
All India Radio copy to:- The Coordinator of IARU-
The Spectrum Manager Mr. Y.K. Sharma Monitoring System Region 3
Akashvani Bhawan, Sansad Marg Manohar Arasu VU2UR
Delhi 110001, Republic of India Bangalore 560060, India
8 February 2009 --- Harmful Interference on Amateur Radio Frequencies
in the 40-m-Amateur Band by All-India-Radio Spurious from 7410 kHz
Dear Sir, The intermodulation product which I had reported 2 November
2007 in Band 7 is again here:
Since the beginning of November 2008 many licensed Amateur Radio operators have been reporting a strong and wideband intermodulation product of All India Radio on the exclusive Amateur Radio frequency drifting between around 7060 and 7070 kHz. The signal strength is up to S 9 + 20 dB, and the signal is about 10 kHz wide. The program is very much distorted with a rocking carrier and difficult to read. It is carrying Hindi (1945-2045 UT) and the General Overseas Service (1745-1945, 2045-2230 UT s/off). I have found the fundamental on 7410 kHz with S 9 + 45 dB and a second spurious signal ("mirror") around 7751 kHz. Also on 7090 kHz there is the same program with S 9 and with clear modulation.
Frequency (kHz) 7060,0 - 7070,0
Date: November & December 2008, January & February 2009
Zeit (UTC): 1745-2230 sign off
Call Sign of Station announcement: This is the General Overseas
Service of All India Radio
QSA: QSA5 (S9+ 20 dB) with a dipole antenna
More info: fundamental found on 7410 kHz, another spurious
transmission on 7751 kHz. (7410 kHz + / - 341 kHz)
Will you please contact the engineers of the transmitter site to fix the problem. The licensed Radio Amateurs of the world have the right to use their exclusive frequencies without the harmful interference of All India Radio.
Thank you very much. I should like to read your answer soon on my screen. Regards, (Ulrich Bihlmayer, DJ9KR, Coordinator of DARC-MS Intruder Watch and Spectrum Control, cc to DX LISTENING DIGEST)
(Via DX LISTENING DIGEST 9-013, February 9, 2009)
New Delhi, India
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