radio telemetry receiver mod.

[raycalvino]

Hello All,

I'm a falconer who uses radio telemetry to track lost falcons. Last year a bought a nice little receiver that works great except for one thing; it has no headphone jack. This is a major problem when I'm out searching for a signal of my falcon when it is windy, or if I'm close to traffic.

I would like to mount a headphone jack on this little unit. I have not taken it apart yet; I thought I would check here for advice first.

My questions are, how do I do this? My receiver has a small speaker; can I just hook on to the speaker?

Thanks,
Ray

 

[Dean Huster]

Adding a headphone jack

In general, yes. Hopefully, this is a plasic case so that the mounting of an uninsulated headphone jack will not be a problem as it would in a metal case if neither speaker wire is grounded.

You can wire the jack so that insertion of the headphones cuts out the speaker or you can wire it so that the speaker still works and the headphone is just added in for your listening pleasure.

Determining which speaker wire is common or "ground" won't be a problem with the plastic case. Simply connect one wire to the "tip" lug of the headphone jack and the other wire to the "sleeve" lug of the jack. I'd suggest a 3.5mm jack for this purpose. In fact, if you use a 3.5mm stereo jack, you can use any of the 'phones commonly used with a Walkman or Diskman, etc. In that case, connect one wire to the "sleeve" lug of the jack and the other speaker wire to BOTH the "tip" lug AND the "ring" lug of the jack, putting both of the 'phone speakers in parallel so you have output in both ears.

If the case is metal, you have bigger problems because you don't want to connect a "hot" speaker wire to the "sleeve" lug or you'll damage the circuitry. In a case like this, you can insulate the jack from the case with a shoulder washer providing you find an appropriate shoulder washer (or its equivalent in little skinny washers) and a jack with a long-enough bushing to make it through all that extra thickness. Then wire it as described above.

If you mount a standard jack directly to the metal case, you'll have to determine which (if any) speaker wire is "ground" and connect that wire to the "sleeve" lug. If it's getting this complicated, you're probably better off not modifying the little box at all for fear of destroying it.

Dean

 

[raycalvino]

Dean,

Thanks for your post. My case is metal, so, after reading what you have to say I feel a bit more cautious. How can a tell which speaker wire is ground and which his "hot?" I should be able to read it with a meter right?

Thanks again,
Jan