Hi Folks,
I have a very workable solution for a Remote Stethoscope to be used to help find under Jeep noises.
First a word of thanks to Dan and Dave for your thought provoking comments. It never ceases to amazing me how much better an idea can turn out when you put it out to folks to consider and contribute their thoughts on.
I went to Wal-mart yesterday and found the solution hanging from a metal shelf 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).
Here is a front and side view of the FRS radios.
To say these two units do the job is a true understatement. I experimented all day and the better part of the night.
Here are some attributes:
- These two units cost $8.64 each. (Wal-mart did have Motorola units that are weather resistant for $14.96 each.)
Each unit 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.
These units have a VOX which is a 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.
They weight 3.1 ounces with batteries. (They are the same size as a Motorola Star-Tec cell phone.)
First thing I did was test them and learn how they operate.
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.
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!
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 5 or 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.
You can hear clear as day shifting the t/case.
Yes you can hear a humming noise as well, like constant background.
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)
I took it over to a friend?s house. He has a bad UCA bushing we are going to replace this weekend. I strapped the unit on the upper control arm and like magic you could hear the thumb clearly.
We then put it on the rear Detroit, and could hear it clicking.
Today I am going to experiment with some mounting systems for this. There is a belt clip on the backside that is removable. It might come in handy as a mounting point., else I will remove it.
I also want to make a foam sleeve, like a pocket that I can slip the unit into and then wire tie or Velcro it on where I want to listen.
I will also try one of my PC boom microphones. Maybe mount a magnet on the bottom of the boom to attach the microphone to the Jeep and use it to point at the drive shaft u-joints.
Let me tell you folks, this works, very very well. Far exceeding the sound quality I was expecting out of my own design. And for less then $20 for both units it isn?t worth it to build my own.
Please let me know of any ideas you have on how to best mount this unit on a Jeep for what you would like to listen to.
Frank
PS: I can see the future now:
?Blaine, here is a MPEG of my Jeep. Can you tell me what that sound is??