It's repeatedly described in the article as "a West-European country", and that it was "close to the border of The Netherlands." That seems to suggest either Belgium or Germany. Is it just to make the location harder for others to find, or because borders are in dispute or have shifted since it was buried?
(Probably unrelated, but I see on Google Maps a forest & bog 20km from the Netherlands border, where the German border appears to be split in two by a Belgian railway line running through it.)
Perhaps the hobby-archaeologist wanted to remain anonymous because unearthing historical artifacts with a metal detector is illegal in some places. In Germany one needs a permit at least and must leave finds undisturbed so that archaeologists can see the context of the find. If the hobby-archaeologist is searching illegally, then he/she may be afraid that the location of the find may lead to him/her.
A question though: how is humidity handled in modern electronics? Is there any sacrificial used on mainboards, or is there any design pattern used on PCBs in general to achieve the same effect?
As modern components are normally much smaller and sit fairly flush with the PCB, there are less nooks and crannies, and so the coating manages to fill them all or bridge them over quite well. It's still not a step used in most PCBs, there are downsides like requiring connectors and switches to be masked off with tape, and so it is reserved for more extreme applications than consumer electronics. Think electric gate control boxes, or marine electronics.
It would probably have existed in some form at the time of the OPs radio, but spraying the PCBs in it wouldn't have saved all the connectors, switches pots and other front panel controls from moisture, and so a more general method was needed.
Finally, a more extreme step is to "pot" the entire PCB by putting it in a sealed container and filling the container with a "potting compound", a liquid resin that sets solid or to a rubbery finish. This makes replacing or repairing the PCB very difficult, requires a lot of thought as to connectors, and it doesn't work well for high power electronics as the potting compound traps heat. It allows you to fully submerse a PCB in water forever, stops sparks if your PCB is working around explosive gases/powders, and is sometimes used as a "security" method in hardware security modules or "secure" USB keys.
For security, potting only really works if tiny wires are embedded in it, which on breaking wipe the encryption keys. Scraping off potting compound can otherwise be done by anyone if they are willing to spend a long time.
For consumer electronics it generally isn't handled. If you look at the edges of the boards you'll see that they are rough-sawn and not sealed and that there is not conformal coating elsewhere on the boards. Note that while FR and hardpaper material are hygroscopic, the epoxy cases of chips let moisture pass as well.
> Digs around in forest for no good reason
> Finds car battery
> Opens it
> Western radio inside
> "Oh shit, a cache of an allied spy. I better put this back where I found this and tell no one ever."
Back in the days no one cared about dumped car parts. But nowadays just about anything raises instant suspicion if anything out of the ordinary lies about on the ground.
> ensuring that anyone who stumbled across it would be suspicious.
Or the person who was meant to retrieve it would know what they found. "It's inside the car battery buried in ..." is a pretty easy instruction to follow.
The instruction can also be hidden in plain sight – a car battery is ordinary enough that no one is going to be suspicious if you write it down on a piece of paper. You can even hide the location in order or invoice number pretty easily.
If someone found it, they may be suspicious. If I found one my first thought would be that is just some junk someone threw out (you can't put car batteries in normal trash where I live). It is fairly easy to notice if dirt has been recently disturbed, even from afar (which his good if you're worried about getting caught).
TL;DR burying something in a car battery is actually pretty clever.
But yes, they tested it:
> The transmitter produces a strong and stable signal at the fundamental frequency, but also produces strong unwanted harmonics, with the f2 being only 3dB down. Furthermore, the f3 is only 10dB down and the f5 is just 20 dB down.
Btw, I think it was Russian not east German and possibly was over the horizon radar or a deadmans switch or something else: we need a /j for joke marking.
"forgotten" it was not - KGB does not forget! just deemed useless to both sides and not worth the extraction risk later on.
also, i wonder if one of Putin's buddies used these back in the days when he was stationed in East Germany in the 80's.
Edit: Just hadn't read far enough...