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Welcome to the next episode of: what-the-heck-is-it?

S

ShakyMcQuiver

Active Member
Apr 11, 2018
69
57
28
Digging through my bone yard looking for goodies and I ran across this. I have no idea when or where I acquired it.
Any idea what it is? I'm thinking a pre-amp or? It has a variable pot (volume or gain perhaps?) It seems to be missing a connector on one end.

The board inside is marked LR-1 and 4-78. The (2) transistors are 2N2222A.
Funny this showed up as I'm having some issues with the pre-amps on some of my small linear amps <twilight zone music plays>.



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PL-259 on one end, missing SO-239 on the other end, has a Red wire and a White wire going out for power.........can only mean a Receive Preamp.

If it did have a SO-239 and was in line with the antenna and radio you wouldn't be able to transmit the radio without possibly burning it up, it would need a bypass circuit with a relay. Could just be someone's experiment.

The trace side has "LR 1" (the builder's initials or their item #) and "4-78" (the build date of "April 1978"?).

You should post a better picture of the component side with what the capacitors are. Also can't see what's on the other side of the Black wire and White wire that are covering that part of the board (if there's anything there or a connection to something else). Then that other Red wire, where does it go, is it part of the missing SO-239? The trace side is good.

Maybe someone here can build one and figure out where the SO-239 connects to/ With some tweaking of parts, it may be customizable enough to get the noise floor down as people complain about that noise so much.

Or list it for sale with all those good words that include RARE a few times...........

73
 
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"words that include RARE a few times..........."

LOL! Yea, I noticed that a lot these days when cruising Fleabay. Sometimes an item is rare, but most of the time it's not... lol.
 
Broadbanded circuit…check
No relay bypass circuit…check
That leaves me with the conclusion that this was made to accompaniment a SWL listeners receiver, particularly those old school receivers that lacked sensitivity above 20 Mhz.
 
Here's some closer pictures...
(I flipped the board left to right for the trace pic).

Thanks again for the replies! I love these mystery CB/Ham forensics! I didn't think about it being a custom job as the board looks factory-like as well as the enclosure. It's plastic and has cooling-like fins on the top. Not sure what good they'd do as I don't think whatever this is would produce any heat to worry about.

And you guys are right... you attempt to transmit through this and it's Kentucky Fried for sure. I noticed that right off the bat too.

As my curiosity got the better of me, I watched a really good vid on Flewtube about a DIY preamp that showed how to set them up correctly with relays so you don't fry anything. It was tiny and he built the whole thing on the back of the relay itself. No PC board. Small and neat!

Very informative vid.

As I mentioned earlier, there are preamps on Fleabay for less than $15. They don't have relays either (or at least I don't think so - they hide the components with shrink tube). I've never used anything like them so I don't know how they install or if they even work that well.


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If it's not identical to ShakyMcQuiver's then it might not be rare, if it is identical then two still could make it rare ........ but on Fleabay it's always rare ....... not medium or well.
 
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