Daless2
06-12-2002, 07:47 AM
Remote Underbody FRS Radio Stethoscope – Under $20
Hi Folks,
At one time or another we all have a noise coming from somewhere under our Jeeps.
Trying to find were a noise is coming from can be difficult to do.
Invariably the noise only happens when the Jeep is moving, or when under load.
This presents a problem, as there isn’t any good, safe way to find a noise other then trial and error, guessing, or putting yourself in an unsafe position.
I have come up with a solution to this problem:
.
.
“How To Safely Diagnose Underbody Jeep Noises, Remotely!”
.
FRS Radio Stethoscope
I went to Wal-mart and found the solution hanging from a metal peg in the electronics department. At a cost of $8.64 each I purchased two “Bellsouth Two Way 22 Channel FRS/GMRS Communicator” (Part number 2231BK).
You will need at least two of these units, one to transmit and the other to receive.
.
.
Here is a front and side view of the FRS radios.
http://www.dana60.com/daless2/frs.jpg
To say these two units do the job is a true understatement. I have experimented for a few days using these units and I assure you, you will be impressed..
FRS Radio Attributes:
[list=1]
Each unit $8.64[/*]
Puts out 500mWatts of power (1/2 watt), which is more then enough to transmit from one unit under the jeep to another unit inside the Jeep. (No license needed for FRS channel use.)[/*]
Units have a VOX (Voice Operated Transmit) mode having 5 sensitivity setting.[/*]
They also have a “Lock Button”, which when pushed disables all the front panel controls until manually released[/*]
There is also a phone jack for a remote microphone.[/*]
Units weight 3.1 ounces with batteries. (They the same size as a Motorola Star-Tec cell phone.)[/*]
[/list=1]
.
.
Initial Testing
First thing I did was testing the FRS radios to learn how they work.
I was quite surprised by the sound quality.
Then I set the channels and wrapped one unit in a covering of ˝ inch foam to pad it and insulate it from vibrations for my tests.
I cut a hole over the microphone area and then wire tied it to my front axle by the u-joint, turn on the VOX, locked the keypad and went for a ride, listening via the second unit inside my Jeep!
WOW!!!!!
I was amazed at what I could hear. I found a ticking noise I didn’t know I even had. Probably time to replace that u-joint.
For the next fiveor six hours I strapped that little radio on everything I could find under my Jeep; Control Arms, Differentials. T/case, Trans, everything I could think of.
The sounds you can hear will amaze you! I attached it to a rear shock and could hear the valve open and close.
On my front axle, I could hear the u-joint and the axle spinning but could clearly hear a ticking that was speed sensitive and became somewhat modified when turning corners as well. (Yup! U-joint going bad and I didn’t even know about it. Couldn’t hear it with my ears.)
I took my radios over to a friend’s house. He has a bad rear UCA bushing we were going to replace. Prior to replacing it we strapped the unit on the upper control arm and like magic you could hear the thumb clear as day.
We then put the FRS radio on the Lower Control Arm on the same side.
The thump caused by the bad bushing could still be heard, but it was no where near as loud.
We then put it on the rear Detroit, and could hear it clicking and could hear my Ox Locker engaging.
The performance of this inexpensive system leads me to believe it would be effective at tracking down a noise by moving and mounting the FRS Radio under a Jeep until a noise comes in most clearly or most loudly.
.
.
.
Foam Mounting
I wanted to figure out a better means of mounting and protecting the FRS Stethoscope to my Jeep’s under-parts besides just wrapping in it ˝-inch foam.
I did this by sandwiching the FRS (stethoscope) radio between two blocks of black closed cell neoprene foam.
I believe this provides these benefits:
[list=a]
Radio protection [/*]
Insulate from vibrations[/*]
Funnels, or channels sound to microphone[/*]
De-forms to shape of what it is mounted to[/*]
Provides a mounting block to strap to an assembly[/*]
Deadens other sounds you are not interested in[/*]
[/list=a]
.
.
Here is a drawing of what I made. (Black foam with a black radio sitting in it does not photograph well enough to see.)
http://www.dana60.com/daless2/foam2.jpg
.
.
Foam Blocks
I used closed cell neoprene foam that I had in my shop. Each block is 1.5-inches thick, 3.5-inches wide and about 5-inches long. The size you will need will depend on the physical size of your FRS radio.
Block “A”
This block has an oval shaped hole cut all the way through it. This hole should be positioned above (in front of) the microphone of the FRS radio. This hole will act as a channel, or funnel for the sound to be directed to the microphone.
Block “B”
You need to carve out a place for your FRS radio to sit in this block B. Put your radio on the face of the foam block and trace the outline with a marking pen. (A Sharpie works well). Then take a utility knife and cut the outline you just traced. DO NOT cut all the way through the foam. Cut only deep enough so that the FRS radio can be cradled within the foam.
With your fingers begin to tear out the foam where the radio will sit. Keep doing this until you can cradle the radio nicely in the indentation you are making.
If you ever plan to use the remote microphone function of your radio you may have to cut a small channel in the foam in order to plug it in. This will depend on where the jack is located on your radio.
As you can see in the drawing above, I put four Velcro tabs on the face of block B. There are four corresponding Velcro tabs on the backside of block A. These are used to hold the bocks together, with the radio inside, prior to mounting the FRS stethoscope under your Jeep.
How To Use
Set both FRS Radio to the (same) channel you want to use.
Activate the VOX (Voice Operated Transmitter) function on one radio. Also set the VOX to the lowest sensitivity level. (You will have t experiment on the sensitivity level for your own radio.)
If you have not already done so, remove the belt clip from the back of the radio.
Place the transmit radio inside the pocket you made in foam block B.
Place foam block A on top of the radio and block B. Press the two together till the Velcro grips.
Mount the FRS stethoscope on the underside component you want to listen to. Please makes sue you have the clearance needed.
I used Velcro straps, bungee cords, nylon straps, and even bailing wire to attach the unit.
Try to press the front of foam block A against the component you want to listen to, in such a way that the foam de-forms around the object. This will seal out other noises.
Start your vehicle, drive it and listen.
If you are not satisfied that you have found the location of your noise simply relocate the FRS Stethoscope and try another location.
Remote Microphone
The FRS radios I am using have the ability to use a remote microphone. This might come in useful if I want to get a closer listen position on high-speed or spinning component like U-joints.
I have tried one of those inexpensive ($3.99) Computer Microphones that come with a 12-inch plastic boom.
I glued a magnet to the base so it would stick to the underside of my jeep.
I can then position the boom so the mic points at a u-joint.
This worked, but would work better if the boom were more flexible. You might want to play around with something like this for yourself.
Please feel free to share any ideas you have on this with the rest of us.
Notes:
The closed cell neoprene foam I used for the block-mounting system held up very well to the temperatures under my Jeep. I mounted the block to axles, differentials, control arms, floorboards, skid plates, t/case, side of transmission, and the bell housing.
I would however be careful not to put it too close to the exhaust system. While I had no problems, I am sure this stuff will melt.
I intentionally dropped one FRS Stethoscope, (wrapped in foam) out of my Jeep on a country highway at 45 MPH. I wanted to see what would happen.
What happened? Nothing!
Radio survived with zero damage.
Even the foam looked good, but boy did it bounce down the road. (Looked like one of the super balls jumping all over the place.)
Folks it takes a lot more power to transmit then it does to receive. If you are using this system and your batteries on the transmit radio are getting weak, simply swap the radios, or the batteries with the receiving radio.
Heat is generated while transmitting. While I did not see any negative effects of this, with the radio encased in the foam, you should be aware of this.
.
.
.
Bottom Line
I am very please with how this work.
For less then $20 total cost I believe this is a great diagnostic tool.
I have actually purchased four FRS radios. I can use three simultaneously under my Jeep on different channels. Then listen in to these FRS stethoscopes by simply changing the channels on the unit I have inside my Jeep.
Plus, when not used for as a remote stethoscope I now have FRS radios to use for their original purpose when I need them.
Any comments or suggestions are welcome and actively being solicited.
I will be doing a small write-up on this in a few days, after collecting any ideas to improve on this.
Frank
Hi Folks,
At one time or another we all have a noise coming from somewhere under our Jeeps.
Trying to find were a noise is coming from can be difficult to do.
Invariably the noise only happens when the Jeep is moving, or when under load.
This presents a problem, as there isn’t any good, safe way to find a noise other then trial and error, guessing, or putting yourself in an unsafe position.
I have come up with a solution to this problem:
.
.
“How To Safely Diagnose Underbody Jeep Noises, Remotely!”
.
FRS Radio Stethoscope
I went to Wal-mart and found the solution hanging from a metal peg in the electronics department. At a cost of $8.64 each I purchased two “Bellsouth Two Way 22 Channel FRS/GMRS Communicator” (Part number 2231BK).
You will need at least two of these units, one to transmit and the other to receive.
.
.
Here is a front and side view of the FRS radios.
http://www.dana60.com/daless2/frs.jpg
To say these two units do the job is a true understatement. I have experimented for a few days using these units and I assure you, you will be impressed..
FRS Radio Attributes:
[list=1]
Each unit $8.64[/*]
Puts out 500mWatts of power (1/2 watt), which is more then enough to transmit from one unit under the jeep to another unit inside the Jeep. (No license needed for FRS channel use.)[/*]
Units have a VOX (Voice Operated Transmit) mode having 5 sensitivity setting.[/*]
They also have a “Lock Button”, which when pushed disables all the front panel controls until manually released[/*]
There is also a phone jack for a remote microphone.[/*]
Units weight 3.1 ounces with batteries. (They the same size as a Motorola Star-Tec cell phone.)[/*]
[/list=1]
.
.
Initial Testing
First thing I did was testing the FRS radios to learn how they work.
I was quite surprised by the sound quality.
Then I set the channels and wrapped one unit in a covering of ˝ inch foam to pad it and insulate it from vibrations for my tests.
I cut a hole over the microphone area and then wire tied it to my front axle by the u-joint, turn on the VOX, locked the keypad and went for a ride, listening via the second unit inside my Jeep!
WOW!!!!!
I was amazed at what I could hear. I found a ticking noise I didn’t know I even had. Probably time to replace that u-joint.
For the next fiveor six hours I strapped that little radio on everything I could find under my Jeep; Control Arms, Differentials. T/case, Trans, everything I could think of.
The sounds you can hear will amaze you! I attached it to a rear shock and could hear the valve open and close.
On my front axle, I could hear the u-joint and the axle spinning but could clearly hear a ticking that was speed sensitive and became somewhat modified when turning corners as well. (Yup! U-joint going bad and I didn’t even know about it. Couldn’t hear it with my ears.)
I took my radios over to a friend’s house. He has a bad rear UCA bushing we were going to replace. Prior to replacing it we strapped the unit on the upper control arm and like magic you could hear the thumb clear as day.
We then put the FRS radio on the Lower Control Arm on the same side.
The thump caused by the bad bushing could still be heard, but it was no where near as loud.
We then put it on the rear Detroit, and could hear it clicking and could hear my Ox Locker engaging.
The performance of this inexpensive system leads me to believe it would be effective at tracking down a noise by moving and mounting the FRS Radio under a Jeep until a noise comes in most clearly or most loudly.
.
.
.
Foam Mounting
I wanted to figure out a better means of mounting and protecting the FRS Stethoscope to my Jeep’s under-parts besides just wrapping in it ˝-inch foam.
I did this by sandwiching the FRS (stethoscope) radio between two blocks of black closed cell neoprene foam.
I believe this provides these benefits:
[list=a]
Radio protection [/*]
Insulate from vibrations[/*]
Funnels, or channels sound to microphone[/*]
De-forms to shape of what it is mounted to[/*]
Provides a mounting block to strap to an assembly[/*]
Deadens other sounds you are not interested in[/*]
[/list=a]
.
.
Here is a drawing of what I made. (Black foam with a black radio sitting in it does not photograph well enough to see.)
http://www.dana60.com/daless2/foam2.jpg
.
.
Foam Blocks
I used closed cell neoprene foam that I had in my shop. Each block is 1.5-inches thick, 3.5-inches wide and about 5-inches long. The size you will need will depend on the physical size of your FRS radio.
Block “A”
This block has an oval shaped hole cut all the way through it. This hole should be positioned above (in front of) the microphone of the FRS radio. This hole will act as a channel, or funnel for the sound to be directed to the microphone.
Block “B”
You need to carve out a place for your FRS radio to sit in this block B. Put your radio on the face of the foam block and trace the outline with a marking pen. (A Sharpie works well). Then take a utility knife and cut the outline you just traced. DO NOT cut all the way through the foam. Cut only deep enough so that the FRS radio can be cradled within the foam.
With your fingers begin to tear out the foam where the radio will sit. Keep doing this until you can cradle the radio nicely in the indentation you are making.
If you ever plan to use the remote microphone function of your radio you may have to cut a small channel in the foam in order to plug it in. This will depend on where the jack is located on your radio.
As you can see in the drawing above, I put four Velcro tabs on the face of block B. There are four corresponding Velcro tabs on the backside of block A. These are used to hold the bocks together, with the radio inside, prior to mounting the FRS stethoscope under your Jeep.
How To Use
Set both FRS Radio to the (same) channel you want to use.
Activate the VOX (Voice Operated Transmitter) function on one radio. Also set the VOX to the lowest sensitivity level. (You will have t experiment on the sensitivity level for your own radio.)
If you have not already done so, remove the belt clip from the back of the radio.
Place the transmit radio inside the pocket you made in foam block B.
Place foam block A on top of the radio and block B. Press the two together till the Velcro grips.
Mount the FRS stethoscope on the underside component you want to listen to. Please makes sue you have the clearance needed.
I used Velcro straps, bungee cords, nylon straps, and even bailing wire to attach the unit.
Try to press the front of foam block A against the component you want to listen to, in such a way that the foam de-forms around the object. This will seal out other noises.
Start your vehicle, drive it and listen.
If you are not satisfied that you have found the location of your noise simply relocate the FRS Stethoscope and try another location.
Remote Microphone
The FRS radios I am using have the ability to use a remote microphone. This might come in useful if I want to get a closer listen position on high-speed or spinning component like U-joints.
I have tried one of those inexpensive ($3.99) Computer Microphones that come with a 12-inch plastic boom.
I glued a magnet to the base so it would stick to the underside of my jeep.
I can then position the boom so the mic points at a u-joint.
This worked, but would work better if the boom were more flexible. You might want to play around with something like this for yourself.
Please feel free to share any ideas you have on this with the rest of us.
Notes:
The closed cell neoprene foam I used for the block-mounting system held up very well to the temperatures under my Jeep. I mounted the block to axles, differentials, control arms, floorboards, skid plates, t/case, side of transmission, and the bell housing.
I would however be careful not to put it too close to the exhaust system. While I had no problems, I am sure this stuff will melt.
I intentionally dropped one FRS Stethoscope, (wrapped in foam) out of my Jeep on a country highway at 45 MPH. I wanted to see what would happen.
What happened? Nothing!
Radio survived with zero damage.
Even the foam looked good, but boy did it bounce down the road. (Looked like one of the super balls jumping all over the place.)
Folks it takes a lot more power to transmit then it does to receive. If you are using this system and your batteries on the transmit radio are getting weak, simply swap the radios, or the batteries with the receiving radio.
Heat is generated while transmitting. While I did not see any negative effects of this, with the radio encased in the foam, you should be aware of this.
.
.
.
Bottom Line
I am very please with how this work.
For less then $20 total cost I believe this is a great diagnostic tool.
I have actually purchased four FRS radios. I can use three simultaneously under my Jeep on different channels. Then listen in to these FRS stethoscopes by simply changing the channels on the unit I have inside my Jeep.
Plus, when not used for as a remote stethoscope I now have FRS radios to use for their original purpose when I need them.
Any comments or suggestions are welcome and actively being solicited.
I will be doing a small write-up on this in a few days, after collecting any ideas to improve on this.
Frank