AirTalk.org Aviation discussions newsgroups   Archives   FAQ   Search   Memberlist   Usergroups   Register   Profile   Log in to check your private messages   Log in  Eliminating Interference          AirTalk.org Forum Index -> Planes, gliders and flying in Australia View previous topic :: View next topic   Author Message Carsten Bauer Guest Posted: Mon Feb 13, 2006 6:26 am    Post subject: Eliminating Interference G'day all, I've setup an ACARS server, connected to my scanner to record ACARS transmissions. But I have a problem with inteference. WHen the scanner is not hooked up to it's rubber ducky antenna, or the 1.2m SCBASE antenna I bought last week, the static is normal, but when either antenna are hooked up I get some interference on 131.550 mhz. It seems to be there around the whole airband and I would like to know how I can track it down? I have turned off every appliance in my house including lights (Fluro and globes) but still cannot eliminate the source of interference. Any ideas would be great. Thanks Back to top Carsten Bauer Guest Posted: Mon Feb 13, 2006 7:39 am    Post subject: Re: Eliminating Interference On Mon, 13 Feb 2006 14:26:10 +0800, Carsten Bauer <spam (AT) iinet (DOT) net.au> wrote: Quote: G'day all, I've setup an ACARS server, connected to my scanner to record ACARS transmissions. But I have a problem with inteference. WHen the scanner is not hooked up to it's rubber ducky antenna, or the 1.2m SCBASE antenna I bought last week, the static is normal, but when either antenna are hooked up I get some interference on 131.550 mhz. It seems to be there around the whole airband and I would like to know how I can track it down? I have turned off every appliance in my house including lights (Fluro and globes) but still cannot eliminate the source of interference. Any ideas would be great. Thanks Recordings of the interference are in my webspace http://www.bur.st/~numloxx/scanner1.mp3 and http://www.bur.st/~numloxx/scanner2.mp3 Back to top Russell Thomson Guest Posted: Mon Feb 13, 2006 10:12 am    Post subject: Re: Eliminating Interference Howdy, This could be pager interference or similar (from your recordings sounds like data bursts). Do you live near a hospital or inner city at all? Cheers, Russell On Mon, 13 Feb 2006 17:26:10 +1100, Carsten Bauer <spam (AT) iinet (DOT) net.au> wrote: Quote: G'day all, I've setup an ACARS server, connected to my scanner to record ACARS transmissions. But I have a problem with inteference. WHen the scanner is not hooked up to it's rubber ducky antenna, or the 1.2m SCBASE antenna I bought last week, the static is normal, but when either antenna are hooked up I get some interference on 131.550 mhz. It seems to be there around the whole airband and I would like to know how I can track it down? I have turned off every appliance in my house including lights (Fluro and globes) but still cannot eliminate the source of interference. Any ideas would be great. Thanks Back to top Carsten Bauer Guest Posted: Mon Feb 13, 2006 7:23 pm    Post subject: Re: Eliminating Interference On Mon, 13 Feb 2006 10:45:09 GMT, GB <g.b (AT) sonicresearch (DOT) mailme.org> wrote: Quote: "Russell Thomson" <rjthomsNO (AT) spamlabyrinth (DOT) net.au> wrote in news:op.s4wpboi6wejkn2@localhost: This could be pager interference or similar (from your recordings sounds like data bursts). Do you live near a hospital or inner city at all? I haven't listened to the recordings, but I've tinkered with ACARS at length in the past. I suggest that the data bursts are the *signal*, not the noise. ACARS transmissions are 2400 bit/s streams AM modulated using 1200Hz and 2400Hz tones. Transmissions typically last for between 0.5 and maybe 2.5 seconds. In this part of the world, 131.550MHz is the allocated frequency. The signal, pumped through a speaker, sounds a lot like an abbreviated version of the sync tones that an early 1200/2400/9600bit/s telephone modem emits through it's speaker before it agrees with the other end and falls silent. GB No, the data is not the noise I am getting. I know the difference between data and noise. The noise is constantly on the frequency. It's 3:20am though and it's all quiet, but during the day something is causing interference. Back to top Harold Guest Posted: Mon Feb 13, 2006 7:43 pm    Post subject: Re: Eliminating Interference "Carsten Bauer" <spam (AT) iinet (DOT) net.au> wrote Quote: G'day all, I've setup an ACARS server, connected to my scanner to record ACARS transmissions. But I have a problem with inteference. WHen the scanner is not hooked up to it's rubber ducky antenna, or the 1.2m SCBASE antenna I bought last week, the static is normal, but when either antenna are hooked up I get some interference on 131.550 mhz. It seems to be there around the whole airband and I would like to know how I can track it down? I have turned off every appliance in my house including lights (Fluro and globes) but still cannot eliminate the source of interference. Just a thought - have you tried turning off your computer monitor, just to see if it is the source of your RFI? Quote: Any ideas would be great. Thanks Back to top Carsten Bauer Guest Posted: Tue Feb 14, 2006 10:01 am    Post subject: Re: Eliminating Interference On Mon, 13 Feb 2006 20:29:15 GMT, GB <g.b (AT) sonicresearch (DOT) mailme.org> wrote: Quote: Carsten Bauer <spam (AT) iinet (DOT) net.au> wrote in news:h3n1v1tct9rltgrc1e9rnc8c5c05dtc6ct (AT) 4ax (DOT) com: No, the data is not the noise I am getting. I know the difference between data and noise. I was responding to Russell, not you Carsten. The 'noise' he described in his post sounds to me like the data. GB Ah my mistake :) Back to top Carsten Bauer Guest Posted: Tue Feb 14, 2006 10:02 am    Post subject: Re: Eliminating Interference On Tue, 14 Feb 2006 06:43:47 +1100, "Harold" <Harold [at] clotmail.com> wrote: Quote: "Carsten Bauer" <spam (AT) iinet (DOT) net.au> wrote in message news:ij90v1hskuumklh2vl4r05orse28i6tde6 (AT) 4ax (DOT) com... G'day all, I've setup an ACARS server, connected to my scanner to record ACARS transmissions. But I have a problem with inteference. WHen the scanner is not hooked up to it's rubber ducky antenna, or the 1.2m SCBASE antenna I bought last week, the static is normal, but when either antenna are hooked up I get some interference on 131.550 mhz. It seems to be there around the whole airband and I would like to know how I can track it down? I have turned off every appliance in my house including lights (Fluro and globes) but still cannot eliminate the source of interference. Just a thought - have you tried turning off your computer monitor, just to see if it is the source of your RFI? Any ideas would be great. Thanks Turned off every appliance in the apartment. and still had the noise. It's quite quiet now, maybe only during certains times of the day it occurs. Back to top Harold Guest Posted: Wed Feb 15, 2006 1:18 am    Post subject: Re: Eliminating Interference "Carsten Bauer" <spam (AT) iinet (DOT) net.au> wrote Quote: On Tue, 14 Feb 2006 06:43:47 +1100, "Harold" <Harold [at] clotmail.com> wrote: "Carsten Bauer" <spam (AT) iinet (DOT) net.au> wrote in message news:ij90v1hskuumklh2vl4r05orse28i6tde6 (AT) 4ax (DOT) com... G'day all, I've setup an ACARS server, connected to my scanner to record ACARS transmissions. But I have a problem with inteference. WHen the scanner is not hooked up to it's rubber ducky antenna, or the 1.2m SCBASE antenna I bought last week, the static is normal, but when either antenna are hooked up I get some interference on 131.550 mhz. It seems to be there around the whole airband and I would like to know how I can track it down? I have turned off every appliance in my house including lights (Fluro and globes) but still cannot eliminate the source of interference. Just a thought - have you tried turning off your computer monitor, just to see if it is the source of your RFI? Any ideas would be great. Thanks Turned off every appliance in the apartment. and still had the noise. It's quite quiet now, maybe only during certains times of the day it occurs. Try asking the aus.radio.scanner newsgroup. Back to top Harold Guest Posted: Wed Feb 15, 2006 1:31 am    Post subject: Re: Eliminating Interference "Harold" <Harold [at] clotmail.com> wrote Quote: <snip> Quote: Try asking the aus.radio.scanner newsgroup. Jeez, I'm slow today ... cancel that suggestion. I see you've already done it. Back to top SR20GOER Guest Posted: Wed Feb 15, 2006 10:14 pm    Post subject: Re: Eliminating Interference "Carsten Bauer" <spam (AT) iinet (DOT) net.au> wrote Quote: On Tue, 14 Feb 2006 06:43:47 +1100, "Harold" <Harold [at] clotmail.com> wrote: "Carsten Bauer" <spam (AT) iinet (DOT) net.au> wrote in message news:ij90v1hskuumklh2vl4r05orse28i6tde6 (AT) 4ax (DOT) com... G'day all, I've setup an ACARS server, connected to my scanner to record ACARS transmissions. But I have a problem with inteference. WHen the scanner is not hooked up to it's rubber ducky antenna, or the 1.2m SCBASE antenna I bought last week, the static is normal, but when either antenna are hooked up I get some interference on 131.550 mhz. It seems to be there around the whole airband and I would like to know how I can track it down? I have turned off every appliance in my house including lights (Fluro and globes) but still cannot eliminate the source of interference. Just a thought - have you tried turning off your computer monitor, just to see if it is the source of your RFI? Any ideas would be great. Thanks Turned off every appliance in the apartment. and still had the noise. It's quite quiet now, maybe only during certains times of the day it occurs. Carsten Just a thought but could be harmonics from something. 1. Check 2 x the freq, 3 x the freq etc and half the freq (all 5 suggestions while the noise is occurring obviously). 2. Check the IF listed for the scanner and check freqs 131.55 plus and minus the IF. 3. If possible, take it to a location at least a few Km away and re-check first for the noise on 131.55 and then the harmonics also. 4. If the noise vanishes in 3 above, try a few different locations if possible and you may discover the source. 5. You can also make a simple dipole - even a 3 element beam if you have enough coathangers - that will allow you to narrow the source down to a direction. We used to do 2 metre ham radio "fox hunts" using a multi element beam on the roof of the car - D/F the source from 2 or 3 locations and then track it down to find the hidden transmitter and win the prize. All depends how hard you want to look. If it is a harmonic or cross modulation, you may be able to fit a bandpass filter (see the ARRL handbook) to siphon off the noise. The problem is that the emergence of wireless technology will probably lead to more harmonic interference. Also if you are anywhere near a hospital, a factory using microwave gear, etc etc, they can be a significant source of broadband noise. Brian Back to top budgie Guest Posted: Thu Feb 16, 2006 2:58 am    Post subject: Re: Eliminating Interference On Thu, 16 Feb 2006 09:14:31 +1100, "SR20GOER" <sr20goerDONTSPAM (AT) ozipilotsonline (DOT) com.au> wrote: Quote: "Carsten Bauer" <spam (AT) iinet (DOT) net.au> wrote in message news:4ka3v19o9abhdl3gt02edve5eb234knct3 (AT) 4ax (DOT) com... (snip) Turned off every appliance in the apartment. and still had the noise. It's quite quiet now, maybe only during certains times of the day it occurs. Carsten Just a thought but could be harmonics from something. 1. Check 2 x the freq, 3 x the freq etc and half the freq (all 5 suggestions while the noise is occurring obviously). Check for what is a half, one third and one fifth of 131.55 - harmonics of THESE will impact. 65.725 is in the middle of ABC2. 43.85 is ??? 26.31 is ?? Quote: 2. Check the IF listed for the scanner and check freqs 131.55 plus and minus the IF. Should be +/- TWICE the IF as that is where IF images come from. Also note that most scanners have several IF's. For images, the first is the dominant susceptibility. Quote: 3. If possible, take it to a location at least a few Km away and re-check first for the noise on 131.55 and then the harmonics also. or try an attenuator on the input. Quote: 4. If the noise vanishes in 3 above, try a few different locations if possible and you may discover the source. 5. You can also make a simple dipole - even a 3 element beam if you have enough coathangers - that will allow you to narrow the source down to a direction. We used to do 2 metre ham radio "fox hunts" using a multi element beam on the roof of the car - D/F the source from 2 or 3 locations and then track it down to find the hidden transmitter and win the prize. All depends how hard you want to look. If it is a harmonic or cross modulation, you may be able to fit a bandpass filter (see the ARRL handbook) to siphon off the noise. The problem is that the emergence of wireless technology will probably lead to more harmonic interference. Also if you are anywhere near a hospital, a factory using microwave gear, etc etc, they can be a significant source of broadband noise. 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