Sunday, January 6, 2008

sources of QRN

Notice: this mesage has been uploaded to my web page of geocities


POWERLINE QRN

A big problem for the DXer

Since last year a very big problem encountered from a strong noise coming from the nearby powerline electricity towers of 22 kV . It first happened about start of June last year and continued until the middle of October. It again started early this May and it still continues this time ( July 2003) with a short pause on June 25 and 26 when it reappeared after a strong lightning YThe level relatively vanished on mid september and is more rare.

For Last year ,as heard , the problem originates from the main transformer’s leakage

You can listen a sample of this noise here as it was before July and how it now is heard

Depending of the band the noise level is a bit different. Here is a listing of the signal levels in tabular and graphical format

Freq MHz Level Att level pwr1.gif (4232 bytes)

1.

7

2.5

2

0

/

3

1

-

4

3

-

5

4.5

-

6

7.5

-

7

9

2

8

9

3.5

9

8.5

1

10

7


11

2


12

4


13

4


14

3


15

1


16

0


17

3


18

4


19

2


20

2


21

5


22

2


It is necessary here to describe the problem with pictures

Before that , once again I must state that my antenna system consists of one horizontal 16m wire and one shortcut dipole with down connection of 16m and inactive dipoles of 16 m

P8130002.jpg (7180 bytes)

P8130003.jpg (5861 bytes)

Here is the picture near to our building . You can see how close are the powerline 110 kV towers .

Not more than 60 m far

Here is the nearby wiring network from electricity and other sources. Not shown the telephonic spources . Quite complicated , huh ?

In order to check if this really comes from the 22 kV electricity towers or from other local source I have travelled a bit to places around my point of ca 800 m far

Here are some results:

P8130004.jpg (6128 bytes)

P8130006.jpg (7185 bytes)

THis is another view of the dual powerlines of 110 kV . 200mm below this poit the QRN sems to disappear.

And here at a point 1 km far from the house and again under the powerlines . Here the noise level is quite high as in my house till the poit of the car then the signal is cleared

. What is funny , the powerline noise disappears from less than 100 m. I think that ist comes due to little wiring …

For the moment , I m overcoming the noise only using the MFJ noise canceller MFJ 1025 that works with two antennas by phasing out the QRN. However in most cases the tuning and phasing is quite tricky as for just a few kHZ off-tune the noise appears again

As in mid september the problem seems to be a little less. Some times it seems big some times less. According to a telcons professor this may come from the insulators of the high electricity towers . Moisture and dust can effect on the quality of the insulators producing sparks between them and the high voltage wires.

Last may (2003) I made a call to the national Electricity company DEI for this noise problem . The officer in charge insisted that I was the first claiming about it, and supposes it is a local transformer problem or due to possible overload from electrical appliances. (but still exists though we are in cold weather and rain for today ) It is expected powerline communications (also known as BPL) to start in late end this year by DEI s daughter company Tellas


UPDATE A2006

As of 2006 the noise was audible only on trhe MW band 500 ca 2000 kHZ band wioth S9 across it The most peculiar of it , the nose was off for several hours in the morning , enabling me foe weeekends to listen to MW



UPDATE 2 - ADSL supposed add-on 11/2006 but !!! .

The recent days (start of November 2006) I have made a request for ADSL line . though I have not been informed by anyone , i found the DX diference. Tjhere was just little QRN across the bands.

However the same days there was another noise added in our area from unknown source The shape levels are determined by a level of S9 on the 2-4 MHz lowering to about 6 mHz , being below S0 for the 6-10 mHz or S3 with 10 db preampplifier and then somehow raised from above the 16 mHz by a nearly constant level of S2-3 on the 17-24 mHz . That happens onthe 2x 16 m antenna

The most peculair is gthat the noise is starting from 1630-1730 LT !!! and contiinues at least till 0130

Using the 16 m horizontal antenna there is a nearly constant level of S2-4 across most bands. on MW the noise is S10 in in ocntrast to S9 of V antenna , and a a harsh audio above the 10 mHz . This caused me an increase of tinnitus however...

IN practive it can mean a relatively low rate of quite harsh noise. In most cases it does not offer big amountrs of nose , but in the lowers bands this noise is absolutely killing radio listening



OTHER SOURCES OF QRN OBSERVED

Several other sources i found so far include:

  • satelitte TV receivers , and most particularly hard disks on sat antennas. I own a Dreambox receiver which in very short time i built-in a hard disk.With the hard disk a rasor sounded noise is heard with up to S3 on the 2x16 m antenna
  • Fluorescent lamps: They add a huge amount of noises , usually S 5-7 . This is the reason , though my older work, that i completey removed them from house.
  • TV set : again i hnave observed very low levels. Most susceptible band comes the 10-11MHz band

And one supposedly adding a lot of noise but was in the reverse:

  • Computer: believe itor not my 3 GHZ computer , with TFT 17", scanner , optical mouse , laser printer etc , did not produce any harsh noises
    • The 17' tft monitor is above the radio and produe very low levels of noise that can annoy only if i have to listen to very poor signals (below S2 with preamp!!!) in the MW and 10-11 MHZ bands
    • Printer adds some noise only when printing occurs
    • The horizontal antenna is more susceptible to any noises generated from any type of sources . BY shutting off computer a white noise generated in the 16- 20 MHZ band is stopped , leveled S2 only

If someone has any idea how to overcome this noise , without using the MFJ canceller, please let me know at

Blogged with Flock

No comments:

Post a Comment