Didn't work. I hooked one up to a TTL-to-USB adapter. My terminal displayed "ERROR". I didn't even bother with the others in package

Guess they fixed all the issues because mine have that "missing capacitor" others were complaining about and there is a known issue with HC-12 clones that you can fix but I tested these for that and they do not have that issue they are perfect. Worked first time with no issues and the range with just the stock spring antenna's is decent so I have to be honest and give 5 stars for the ones I received.

As other reviewers have noted, there is a capacitor that is not populated on the board according to the board's silkscreen. You can tell that it's a capacitor by looking at images of *other* essentially identical implementations of this board - you'll see more or less without exception that there's a capacitor there. The capacitor goes between the antenna lead and ground if my probing was accurate.My initial thought was: this is going to be an exercise in futility, because I've never worked with these boards before; I don't now how they're *supposed* to work and if they came pre-broken I'm going to get super frustrated.So the first thing I did was to take two of the four boards and solder in some 10nf ceramic caps (that was a guess - gpt helped me choose it). I then set those up on a couple breadboards with usb to serial uart breakouts and wrote a little code to do bi-directional traffic between them. They only had 6cm of separation between the antennas - but - they worked.So then I'm thinking - well - hunh. And I replaced one of the "repaired" ones with a "stock" one (that has no cap in that position). Still worked. I separated them by 1m then 10m between building floors, and then 20m between building floors. Still worked. So I replaced the other "repaired" one with a "stock" one (so that neither of the two boards have my "repair") - and ... they still worked with 20m and two floors between.I've included a photo of my test setup. This is the second test in which I had one board that I "repaired" by adding a 10nf cap to that part of the board, the other was left "stock".Now I'm in the awkward position of saying "these work well for my use case". It's awkward because as I said I have no prior experience w/ these boards and it does seem absolutely true that there's a filter capacitor missing from the RF side of this thing according to the device's own silkscreen and countless images of other versions of this board. That *should* affect its sensitivity to high frequency noise and it probably should affect distance as well.But I don't see a problem, so - they get all the stars.Someone who *does* work with these boards can probably get into more depth - maybe there's a problem with range that not having that cap introduces.[UPDATE]I bought (not through vine) another four of these and found that of the four, only one worked. On close examination, the ones I recently purchased are on a different pcb with a different chip and with different mask lettering. This is much more in line with other reviews, so I'm deducting 3 stars. I'm half wondering if this is grab bag of QC rejects. :([SECOND UPDATE]I've increased my rating for these HC-12 boards to 4 stars. The reason for that is the following:Since I first encountered these boards, I was not aware of an issue that is apparently actually pretty well known: there are two "versions" of the HC-12 module, differentiated by different firmwares, each of which are incompatible with the other. Apparently this has been true for some time and is now just an unfortunate "fact of life" with these things.So - if you buy THESE boards and keep sourcing from THIS source and assuming this source does not come into a batch of the "other" firmware, you'll get a bunch of pretty low priced HC-12 modules. In fact this seller has (afaict) among the best prices for these out there.My philosophy on these given the above has changed to: stock up on as many as I think I'll want to build into the future and test every batch for compatibility.I very recently purchased an additional 8 HC-12 modules from this seller. All but one of them works right, and they all work together. So I'm buying more.

We use these HC-12 modules all the time so we know when they work or don't work. I was amazed to find out that all 4 of the supplied items didn't work, there needs to be some quality control somewhere.

Product is not working because capacitor is missing