Scanning and Interference

[Jason]

Hello All.  I currently own a Uniden Bearcat 780XLT (27 Bands from 25 MHz - 1300 MHz with 500 channels).  It is hooked up to an external Outdoor Scanner Discone Antenna with the same range of bands as the scanner.  I have ran into a few problems.  I could only install the antenna in the attic.  I live about 13 miles to the Northwest of KBDR (Bridgeport).  When my computer is turned off I am able to pick up about 5-10 NY frequencies, 5 Boston as well as KBDR ATIS, Tower, Ground and KOXC ATIS.  When my computer is turned on (quite often) I am not able to pick any transmissions up from ATC.  I have a feeling it's because of computer radio waves, but when other computers in the house are turned on it works fine.  Any suggestions on what to do?  The scanner is about 3 or 4 feet away from the computer.  I can always move the scanner further away and get a longer coax cable if need be.

Thanks,
Jason

P.S.  Congratulations to Ed (PHL_Approach) a friend of mine who recently has the KNXX feed going!  Great job Ed!  Nice and clear!

[dave]

Jason-

As you've discovered, computers produce man-made noise.  It could be your computer or it could be your monitor.  Most likely it's the computer and its power supply.

The only thing you can do is get that antenna as far away from the computer as possible, ideally outside the house.

We'd love to get some of those Boston Center and New York Approach feeds from you some time...and KBDR.

-dave

[Jason]

Hy Dave -

Thanks.  I'll see what I can do.  I have the antenna over 100 feet away from the computer... Do you think moving the scanner further away would help?

Jason

[dave]

Hy Dave -

Thanks.  I'll see what I can do.  I have the antenna over 100 feet away from the computer... Do you think moving the scanner further away would help?

Jason

It depends on where the noise is coming in.  Most likely it's coming in through the antenna, though.  The other thing you can try is passing the audio cable (if you're using one) through a toroid.  But I doubt that will help given the way you described the noise.

Good luck!

Dave

[Jason]

Ok.  Thanks.  I'll see what I can do about moving it.  The odd thing is that when other computers are on in the house it does not affect it.

Thanks once again!

Jason

[dave]

Ok.  Thanks.  I'll see what I can do about moving it.  The odd thing is that when other computers are on in the house it does not affect it.

Thanks once again!

Jason

Those other machines may have better power supplies (better shielded).

-dave

[Jane G]

Jason,

I have a very similar problem. Same scanner and an externally mounted Discone antenna. But it's most definitely the Monitor that severely interferes with my 780XLT. When I switch on my PC & Monitor I must wait approx 5 minutes before switching on the scanner. Otherwise the squelch is effectively disabled and all you can receive is hash. The interference is greater where the colour of the monitor screen is closer to white. It also affects my BearCat 245XLT.

I suspect that it's some form of emission from the monitor that peaks when first powered up then dies away. Anyone have any ideas?

Cheers

Jane G

[Jason]

Hi Jane.  I turn off my moniter when scanning but it serves no effect on my scanner.  I have a coax running from my anntenna in my attic down the walls to my room whic then stops like a phone line and then a coax coming out of the wall-plate.  I think I'm going to try to replace the external coax and see what happens.  The coax might not have enough insulation.

It also does not interfer with my scanner when my computer is offically off.  I tune my scanner into KBDR ATIS and when my computer spools up I loose it and will not come back until my computer is swited off.


Jason

[Jane G]

Hi Jason,

I am by no means a technically minded airband enthusiast but having picked up a couple of handy hints from those in-the-know along the way I can only suggest the following;

You mentioned earlier that the antenna is 100 feet away from the scanner. This may present some serious problems. In my experience the further the distance between the antenna and scanner the poorer the reception. The greater the distance of the coax cable the poorer the reception. The cheaper the coax cable over such a distance the poorer the reception. The smaller (in diameter) the coax cable the poorer the reception.

And maybe the location of the coax cable in reference to mains electricity "may" also have an influence on reception.

Jane G

[Jason]

Thanks for the tips. The fact is that I cannot move the antenna any closer.  I get fine reception where the antenna is, but it is the computer interference knocking the reception out.

Jason