Author Topic: Airband bandpass filter  (Read 4918 times)

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ferluq

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Airband bandpass filter
« on: May 07, 2010, 10:40:12 AM »
Hi everybody. Currently I'm living in central Paris, surrounded by buildings and I imagine many radio sources, and my venerable Yupiteru VT 125 II only gets constant white noise, unless I put my hand around the base of the antenna. I'm thinking about buying this http://www.radioworld.co.uk/~radio/catalog/abf128-airband-filter-p-6213.html?osCsid=42cd4f31a0f8fe72dc61dd3340efa287 . Do you think it might help?
I've always read great things about the Yupiteru (being a dedicated airband scanner), but it doesn't have the 8.33 stepping, shutting me out from many freqs. in Europe, should I be thinking of upgrading? How widespread, worldwide, are the 8.33 freqs.?
By the way, I just bought the PlaneGadget Radar receiver, and when you see on PP a few planes (again my location it's not the best) around Paris from sharer hQ, that's me.
Thanks for any help.
Cheers,
Fernando
« Last Edit: May 07, 2010, 11:18:04 AM by ferluq »

Anmer

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Re: Airband bandpass filter
« Reply #1 on: May 08, 2010, 01:47:59 PM »
Hi Fernando

Do you have a different antenna to try first?

ferluq

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Re: Airband bandpass filter
« Reply #2 on: May 08, 2010, 02:02:14 PM »
Thanks for the reply. I'm using a Maldol AL-500H. It really has to do with my location around the house, mostly I have no problems. But, since I'm trying to receive and decode acars signals, when around the computer there's only white noise, no squelch well help. It's probably interference from the computer itself, bu then I wouldn't be able to connect the scanner to the computer.
Cheers,
Fernando

Anmer

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Re: Airband bandpass filter
« Reply #3 on: May 08, 2010, 03:06:59 PM »
I use my Sony Air7 and AOR 82 next to my computer?

Maybe someone else has some comment.

Keith D

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Re: Airband bandpass filter
« Reply #4 on: May 08, 2010, 10:55:38 PM »
Hi
Friend of mine had all this before he moved
his was eventually traced to 2 things

1] the antenna feeder cable being to close to his computer SCREEN!!!
also the computer box was not helping.

moving the feeder cable and scanner further away started to help
we just made a longer cable from the scanner to the sound card
we also made this up from really thick speaker cable with a tight woven outter screen
of the coax like cable not the usual twin speaker cable

this also helps to earth the scanner which i know yours has a plastic cover

we began to hear some beeeeeps

2] we also found he had a mobile phone mast about 400 yards away ontop of a water tower
he then got an airband bandpass filter

between the 2 changes we got his acars system working well

now another thing i remember from the acars days was people found and reported
another senario
having the antenna directly or near directly above the computer and screen and quite close
i.e. antenna in loft and computer and screen in upstairs room below antenna

by moving the antenna abourt 2 meters to one side was the cure here--apparently

i have a band pass filter here somewhere which i used as i was getting grief from the central heating water pump
which was just thru the wall of the playroom here it was not the exact same as the one you show
but it worked very well in both my and my pals location

i will try to find it tomorrow morning and see if it has any maker or ID markings on it

one thing you could try is if you still have it put the rubber dick antenna on it and have a walk around
outside

what gives ???

any worse in one location than another ??

as a last but not yet
what feeder cable are you using it needs to be 50ohms low loss and have a really tight woven out screen
cable like analog TV cable is useless as the outer screen is like a string vest
and lets everything and its brother thru to the inner cable

hope this helps a little

cheers for now

Keith D.
« Last Edit: May 08, 2010, 11:03:50 PM by Keith D »

Keith D

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Re: Airband bandpass filter
« Reply #5 on: May 09, 2010, 12:11:50 PM »

Hi

Found my band pass filter
looks like an earlier version of your suggestion

AOR ABF125

While i have the key i have the same scanner as yours here
have you got the external power supply for it
if yes

try it with a set of batteries installed then insert the external power supply turned on
now what gives with the squelch with radio on 131.725MHz

cheers

K/

ferluq

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Re: Airband bandpass filter
« Reply #6 on: May 09, 2010, 05:26:53 PM »
Hi Keith, Actually I've tried both ways, with the power supply and without it, just the fact that I plug the scanner, either to the lead or the computer, will blanket with white noise the signal, which any other way it's quite clear. It's a bit frustrating to clearly hear the acars beeps but not being able to process them. The audio cable it's 3 mts long, but just by getting the plug near the scanner will generate noise. I'll keep trying different combinations, let's see what gives.
Cheers!

Keith D

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Re: Airband bandpass filter
« Reply #7 on: May 09, 2010, 07:33:35 PM »
Hi Keith, Actually I've tried both ways, with the power supply and without it, just the fact that I plug the scanner, either to the lead or the computer, will blanket with white noise the signal, which any other way it's quite clear. It's a bit frustrating to clearly hear the acars beeps but not being able to process them. The audio cable it's 3 mts long, but just by getting the plug near the scanner will generate noise. I'll keep trying different combinations, let's see what gives.
Cheers!

Hi

no theres something else wrong here
many people who live in 1 acars freq areas leave the squelch fully open[max hiss]

all you do is connect it too the sound card line in socket and mute the speakers
you should get decodes like this if you can hear the beeps so can your soundcard and software

what software are you using  ACARSD ??

i use shielded cable for the lead from scanner to soundcard
dont forget you need mono plug for scanner end and stereo for the sound card end
solder the centre core wire if lead to both the small/short tags in the stereo plug
so you connect to left and right hand channel

heres the cable i use

http://www.maplin.co.uk/Module.aspx?ModuleNo=97990

when you buy the mono and stereo plugs make sure the cap has a large enough
hole to allow cable to enter.you can see in the picture the outter shield is knitted  solid to stop extrenal RF
getting to the solid copper centre core

now keep the scanner as far away from computer and screen as possible

cheers

K/
« Last Edit: May 09, 2010, 07:36:49 PM by Keith D »

VK2GEL

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Re: Airband bandpass filter
« Reply #8 on: May 10, 2010, 12:11:48 PM »
http://www.garex.co.uk/vhf_accs/vhf_accs.htm

http://www.ssejim.co.uk/21-airband.htm

Try torroids on your power and audio cables, and also a switch mode scanner power supply.

ferluq

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Re: Airband bandpass filter
« Reply #9 on: May 10, 2010, 03:23:59 PM »
http://www.garex.co.uk/vhf_accs/vhf_accs.htm

http://www.ssejim.co.uk/21-airband.htm

Try torroids on your power and audio cables, and also a switch mode scanner power supply.
Thanks for the idea. I'll try using ferrites and will tell you guys how it goes.
Cheers.

Keith D

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Re: Airband bandpass filter
« Reply #10 on: May 10, 2010, 06:02:38 PM »
Quote
Thanks for the idea. I'll try using ferrites and will tell you guys how it goes.
Cheers.

If you are using twin cable and not shielded cable that i am afraid will do nothing

K/
« Last Edit: May 10, 2010, 06:04:19 PM by Hamish McTorsk »

ferluq

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Re: Airband bandpass filter
« Reply #11 on: May 15, 2010, 04:37:05 PM »
Hi guys,
Just to let you know that the ferrites did work. Now I'm just trying to guess the correct level for the audio signal. I get the nice boxy shape in the signal window in PP, l¡hear the beep through my speakers, but no signal is decoded. Will keep on trying.
Cheers,
Fernando

Keith D

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Re: Airband bandpass filter
« Reply #12 on: May 16, 2010, 08:17:10 AM »
Hi guys,
Just to let you know that the ferrites did work. Now I'm just trying to guess the correct level for the audio signal. I get the nice boxy shape in the signal window in PP, l¡hear the beep through my speakers, but no signal is decoded. Will keep on trying.
Cheers,
Fernando

Dont know which acars software you are using but i have a here a small add-on programme for the signal strength
for this

problem is i dont know where i got it after all these years

if it will help if you send me a PM with your direct e-mail address i will send it to you as .ZIP
its only small 345KB [172 zipped] i leave it sitting on my desktop
and run it from there

if Anmer or Hamish reads this if you think a copy of it is worth a place in the files section here
let me know and you can have a copy to place there
i have found it very usefull its so easy to overload a soundcard and create distortion and lack of decodes


cheers

K/


Anmer

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Re: Airband bandpass filter
« Reply #13 on: May 16, 2010, 08:30:04 AM »
if Anmer or Hamish reads this if you think a copy of it is worth a place in the files section here
let me know and you can have a copy to place there
i have found it very usefull its so easy to overload a soundcard and create distortion and lack of decodes

We're happy to host any relevant resource as long as it's approved by the IPR owner.

Keith D

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Re: Airband bandpass filter
« Reply #14 on: May 16, 2010, 09:23:05 AM »
if Anmer or Hamish reads this if you think a copy of it is worth a place in the files section here
let me know and you can have a copy to place there
i have found it very usefull its so easy to overload a soundcard and create distortion and lack of decodes

We're happy to host any relevant resource as long as it's approved by the IPR owner.

well the answer here is that these meters where made something like 8 to 10 years ago
they spent most of there lives in the ACARSD yahoo group files section
as to who created them that may well never been known he/she may not even be alive
there is no way to find out.

if you dont want them fine

anyone need or want it send me direct PM the files is all yours

K/
« Last Edit: May 16, 2010, 09:24:42 AM by Keith D »