LS-685/U

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Useful Modifications

Al Klase - N3FRQ 10 May 2012


Most back-pack radios were not designed for loudspeaker operation, but there are a lot of situations where a speaker is a handy addition. Something like an LS-166 will plug right in, but there generally isn't enough audio to make it as loud as you'd like. Plus, the damn thing weighs 3 1/2 pounds. (Just the thing for hand-to-hand combat.) Alex, K2AJR showed up with an LS-685 at the recent MTA meet in northern NJ. He later emailed me regarding an E-bay seller who had them two-for-$20, shipped. I ordered a pair immediately. They arrive the other day. This speaker was designed to be used with some component of the Singars family. It's plastic and weighs 1 pound. The connector is wired strangely, and was designed to NOT mate with the standard U-228 we all know and love.


Disassemble the connector, and move the wire on PIN-E to PIN-B. While the connector is apart, grind away the extra locking lug adjacent to PIN-E. This make it a U-229 equivalent. The cord on the first speaker I worked on was defective., There had to be some reason the Army threw it away.


Connected to a PRC-77, the LS-685's acoustic output measured within a dB or so of my LS-166. However, when connected to my PRC-104 the LS-685 was 10dB louder, a welcome improvement. A quick measurement of the speakers impedance showed 200-300 ohms, versus 600 for the LS-166. So if the radio has a lower output Z, this speaker will be louder. 6 ounces of the weight of the stock speaker is the heavy shielded coil cord. I went with a lighter cord, and cut the total weight to 11 ounces. The speaker has a built-in belt clip on the back, which in turn has a key-hole punch out that can be hooked over a handy screw. I think I like it!



Adobe PDF icon.png Useful Modifications by N3FRQ (same as above)