Intruder Watch

Chapters this page:-

Preamble. - The Real Culprits. - Monitoring Equipment. - Spectrograph Software. - IARU Monitoring Network. - Sample reports.

Listening to the amateur radio bands, I have become aware of various intruders. These range from wall to wall CB type chit chat on 10 meters, to continuous telecom calls on 40 meters. There are times when the so called illegal operator appear on other bands. Broadly, in this region, intruders consist of regular telephone circuits, fishing trawlers, and many unlicensed operators possible using HF for day to day business.

Another source of interference is from power line type noise. This is considered serious, as it prevents, or blocks out all amateur DX signals on the HF bands. Knowing that power line noise is a possible sources of blocking I began to investigate the causes. In my attempt to clean the station of power line QRM, I spent almost one year searching and analyzing the situation. The list of procedures I undertook are covered in the appendix at the bottom of this page.

Having satisfied myself that the station was clear of transmit TVi and locally generated QRM , I began to monitor condition on a daily basis. This involves noting date time frequency and prorogation condition. It became apparent that apart from the unlicensed intruders there was a far greater underling sources of interference.

The Real Culprits
This interference belongs to all sorts of broad band generated signals, which unless carefully listened for, can go un-noticed. As the band noises come and go with propagation and are none existence when the bands are dead, it was fingered out that some very powerful transmission are occurring on a daily basis.

I reported these observation to a RAST committee member who suggested that I join the IARU monitoring services as the coordinator for Thailand. I accepted this position in June of 2003 and have continued as much a circumstances permit. The duty consists of submitting monthly reports to the regional three coordinators in India. Who in turn sends collected reports to the region three directors. These reports are then posted onto the IARU wed site.

Whilst intruders of the type described above can be classified as amateurs, I don't consider them to be a serious long term threat to our allotted armature bands. Local rules and regulation and policing of this type of interference will eventually prevail.

My main concern are the professional intruders who have a commercial interest in making QRM. These include atmospheric sounder, over the horizon radar (OTHR), weather radars, coastal intruder radars, sea state transmitters, fishing markers buoys, official jamming station, and military traffic encrypted signals, just to name a few.

Monitoring Equipment
At my QTH here in Chiang Mai Northern Thailand I use a Kenwood TS940S which is one of the few rigs that is type approved by the licence bureau in Bangkok. The antennas comprises of an 80 meter dipole at 80 foot and a 40 meter dipole at 50 foot. Both coaxial cable are type UR67 feed up the mast to an antenna switcher unit. The HF antenna for ten, fifteen, and twenty meters is a two element Cubex quad. Again UR67 cable from each element, is feed to the switcher unit. A single LDF4-50 solid coaxial runs down the mast to the shack along with the control cables.

The antenna systems and rig hears very well, and picks up motor bike ignition on the main road some 300 meters away when the antenna is point in that direction, on ten meters. The other antennas normally lift the S meter several point when pointing to the daylight zones.

Spectrograph Software
My interest in monitoring strange noises was increased by the ability to actually see the interference, which is in most cases sounds just like white noise. There are many spectrum scopes programs available for free downloading. All utilize the computer sound card and connected to the rigs audio output source. The pictures produced are stunning in showing the audio spectrum and can be saved to any JPG file for reference, as well as the sound tracks, in MP3 format.

IARU Monitoring Network
The world network of IARU monitoring stations is vast, coordinator and action taken by way of feed back is unfortunately minimal, as is removal of intruders by way of prosecutions etc. The situation is one of political boundaries and whilst all country agree to abide by the rules of non interference, good diploma often overrides these commitments.

Sample Reports
The following are sample reports posted on the IARU web site and intended to highlight the enormous task of cleaning up our amateur bands. The first is written by our region three coordinator VU2UR and clearly outlined in a nutshell the work ahead.

I have also included spectrograms and sound files recently recorded at this QTH. It is interesting to note that these pictures closely agree with similar pictures appearing world wide, not just from monitoring stations, but by amateurs interested and very well qualified to name the type of transmission, modulation mode, and most likely countries.

I hope that this page has been informative and I encourage you search the WWW for further details about this subject.

Good Hunting.

IARU Reports and Log Samples.
From Asasu VU2UR Region 3 MS coordinator reading
From HS0ZEE MS coordinator for Thailand Good Stuff
Special IARU contest report 2005 Very Heavy reading.
Sample log in XLS, zip format Contains some special formatting.

Other Items
Pictures files of QRM:-
Display groups ( 1 to 3 ) ( 4 to 6 ) ( 7 to 9 ) ( 10 to 12 ) ( 13 to 15 )

Sound files in MP3 Zip format:-
(Fish Nets 80k.) (Drift Nets 85k.) (40 Meter Nets 98k.) (7.045Khz 127k.) (14.137Mhz 175k.) (14.270Mhz 179k.)

OTHR Transmission.
Manufacturer explain how and why

TVi Interference - Basic.
Description about better reception

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