making a noise sniffer
Printed From: the12volt.com
Forum Name: General Discussion
Forum Discription: General Mobile Electronics Questions and Answers
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=104164
Printed Date: April 27, 2024 at 11:41 AM
Topic: making a noise sniffer
Posted By: silentblackhat
Subject: making a noise sniffer
Date Posted: April 21, 2008 at 5:45 PM
Hey guys I am trying to figure out how to make the "Walkman Noise Sniffer" so i can solve a noise problem thats being radiated into my CB radio antenna. i get how to do it generally but i need some help. Heres how it basically works: 1.) Get an old AM/FM/Tape walkman 2.) Remove the tape head inside(unsolder it). Some say solder it to the tape head, some say remove it and solder the extension wire to the connections but im not sure what connections. I heard there area few 3.) Extend the tape head connections with an antenna wire (some say shielded antenna wire and some instructions don’t say 4.) Strip 1inch off the end of the extended wire 5.) Press "play" on the walkman tape part and the extended wire will pick up the radiated noise. The louder the noise is in the walkman headphones, the closer u are to the noise source. The only thing that i don’t get is it says to solder the antenna wire to the tape connections but: 1.) if its shielded wire, do i just solder the main wire inside to the tape head connections or do i have to so something with the shielding also? Any help is greatly appreciated!
Replies:
Posted By: i am an idiot
Date Posted: April 21, 2008 at 6:52 PM
You need to solder the Head to the end of the wire that you used to extend it. I would use a shielded patch cord, it is much more flexible than an antenna cable. You really need to wire the 2 heads in series for added sensitivity. when you removed the head from the walkman, was it connected to a flat ribbon cable, or were there several wires connected to it? How many terminals are on the back of the head?
Posted By: silentblackhat
Date Posted: April 21, 2008 at 10:38 PM
The one I currently took apart is a ribbon type. This part confuses me even more after seeing it. Do you know what prong(s) need to be soldered? Also when you say "shielded patch cord" do you mean a cord like CAT5e cable? Here are some pictures: Just for measure if you know what prongs need to be soldered, i numbered them:  This one is the top view taken off. It looks like "1, 4 and 5" are all connected on the same circuit path as you might be able to tell.  
Posted By: i am an idiot
Date Posted: April 22, 2008 at 3:07 AM
By a shielded patch cord, I am referring to an RCA cable. A cheap flexible cable would be best for this application. You are correct that 1,4 and 5 are connected together. 1 and 4 are the grounds of the 2 individual heads and 5 is to ground the outer case of the head itself. I have never built one of these, so I do not know if we need to ground the case of the head, or need to leave it ungrounded for greater sensitivity. When soldering the wires back to the head we need to provide a little loop or jumper on the 5th terminal, it needs to be easy to cut in case it needs to be. On the head itself after removing it from the cable, you need to run a jumper from terminal 1 to 3. This will be the wire to series the 2 heads. You need to connect the jumper from 2 to 5, leave enough slack so it can be cut if needed. Connect the center conductor of the RCA cable to 4 on the head. Connect the shield of the cable to 2 which also has the jumper going to 5. Now for the Ribbon cable end. You need to be very careful to not tear the ribbon, You need to find something to mount the RCA cable to so it will not pull on the cable. Pads 2 and 3 of the ribbon cable need to be connected to the center conductor of the RCA cable. The shield of the RCA cable needs to be connected 1 or 4. That should do it. I started drawing a diagram for you, with your thorough answers so far I am assuming that you will not need the diagram, but if you do just let me know.
Posted By: i am an idiot
Date Posted: April 22, 2008 at 3:34 AM
Posted By: silentblackhat
Date Posted: April 22, 2008 at 2:42 PM
Thanks for the reply. When you refer to the pin numbers on the player head, are they the same exact ones that correspond to the numbered prongs on the picture that i posted? If it does then i am a little confused by the picture made showing the connected RCA cable between the head and the ribbon. On the ribbon the center connector is connected to pics 2 and 3(which i understand) but on the reader head its connected to #4, which is the ground point, but wouldn't the RCAs center be connected to where prongs #2 and #3 on the tape head used to connect to?. I get that the center needs to be connected to 2 and 3 on the ribbon but i am confused why its different on the read head.
basically what im saying is, are we just trying to extend the tape head out from the ribbon kid of like using an extension cord to extend something out like an electrical outlet extension cord? if so, wouldn't connect #2 and #3 together on the ribbon and connect it to #2 and #3 that would be connected together on the read head(this connection being made by the center wire on the RCA). then solder #4 to #4 on the read head using the 'ground' wire on the RCA while soldering a connection between 4, 5 and 1 on the read head so they will all get the ground connection from when i solder #4 from the ribbon to # 4 on the read head.
Posted By: i am an idiot
Date Posted: April 22, 2008 at 7:58 PM
We connected the heads in series, to give you more voltage output. I just used pin 2 as the ground, only reason was that it was next to terminal 5 which is the ground of the case of the head. Figured it would be easier to put the jumper. You can try it without running the heads in series, but I really think the extra voltage will be a plus.
Posted By: jmelton86
Date Posted: April 22, 2008 at 8:08 PM
You can still use the volume control, right? So, the extra voltage will be useful indeed.
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2013 Kia Rio -90a alternator
DDX470HD GTO14001 GTO1014D (x3)
Big3 in 1/0G
1/0G to GTO14001
Posted By: silentblackhat
Date Posted: April 22, 2008 at 9:56 PM
I might be looking at the diagram wrong...The problem I am having is not the picture of the ribbon part but the tape head part; basically i dont get why its connected where it is on the tape head side.
I definitely get that connecting #2 and #3 together and then connecting the center connector to that connection is a good thing on the ribbon. What i don't get is why the tape head part is wired the way it is.
I don't get why #2 and #3 on the tape head aren't connected together with the center conductor of the RCA running to that connection. instead the center conductor from the #2 and #3 connection from the ribbon is connected to #4 on the head which is a ground point. Also #3 is connected to #1 on the tape head where #1 is a ground point. #2 on the tape head is where the RCA's ground wire is connected.
I may be looking at it the wrong way though 
Posted By: i am an idiot
Date Posted: April 22, 2008 at 10:13 PM
Posted By: silentblackhat
Date Posted: April 22, 2008 at 10:58 PM
I think you and I should switch screen names...because its true for me.
I think if i look at it long enough ill figure it out...im just not getting it for some reason...im just confused on why the head is wired the way it is because the center connector is connected to #2 and #3 but on the reader head its connected to what was connected to a ground point when it was connected to the ribbon directly. and what is a ground point on the ribbon is connected to #2 on the reader head which used to not be a ground.
I think(if you are able to i would appreciate it) if you could explain the flow of electricity it would help me understand it. I think what im not getting is how its wired in series. I know what series is but for some reason im not getting it. I can easily follow the diagram and wire it exactly like that, its just i would like to understand how its working.
Posted By: i am an idiot
Date Posted: April 23, 2008 at 7:02 PM
I am thinking that you will need the extra voltage that wiring the heads in series will provide. If you are familiar with wiring a set of speakers in series, you know that you have to connect a positive wire from one speaker to the negative wire of the other speaker. This is exactly what we did here. 2 and 3 were positive and 1 and 4 were the grounds. As long as this is the only transducer in the circuit, it only has to be in phase with itself. Just for a convenience when building it I used pin 2 as a ground. I did that because of it's proximity to the head ground, pin 5. Since I used 2 as a ground, that makes 3 a ground also. Thus making 1 and 4 positive. The path of the electricity in the first diagram I posted goes as follows. 4 is the positive that is connected internally to 3 which is now a negative, we ran a wire from 3 (negative) to 1 (positive). This is the series conenction. 1 is internally connected to 2. Which is now our ground. As I stated earlier I reversed the phase of everything in order to have the Head case ground close to the final ground of the 2 individual heads. I didn't think you were going to look so deep into it.
Posted By: silentblackhat
Date Posted: April 24, 2008 at 4:43 PM
I try to 100% understand what im doing before I do it so i can learn from it as well as not go into something bliindI totally get it now; i feel like an idiot for not seeing it. I will build it tonight and see what happens Thanks again!
Posted By: silentblackhat
Date Posted: April 28, 2008 at 10:22 PM
Well here it is wired up, looks like crap but its 'electrically sound'; i made sure to test everything with my multimeter....but the good news is that it works! Thanks!
In this picture, ignore the green wire thats connected, it leads to nothing
The finished product
Posted By: jeffwhiteman
Date Posted: April 29, 2008 at 8:03 AM
nice work guys! I am curious if were able to isolate the noise problem?
Posted By: silentblackhat
Date Posted: April 29, 2008 at 10:24 AM
well i actually just made it last night and tested it quickly. It does seem to be coming from the ignition wires and distributor though. I will post what I find out soon
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