Are vent holes a good idea though, do they open a vector for stray signals etc?
Also, do I need to ground the dongle inside the case, or anything else?
(Im planning on filing down to bare metal on the case, and maybe even filing the PCB down carefully if needed to fit).
Vent holes will allow some RF in, though there is fairly complicated math to calculate how much shielding one gets from such and such sized holes and such and such a frequency.
That said - if cooling is a real concern (i’m not sure this stuff gets hot enough for it to be) the furrowed sides of that box will make a nice heatsink if you use thermal pads on the chips ant stick it to the case.
For the case to be an effective shield it should be electrically connected to the shield of the cable. If your dongle uses an MCX to SMA pigtail, getting a “bulkhead mount” pigtail and using the nut to secure the SMA connector through the hole you drill will accomplish this nicely.
I don’t think you’d need vent holes, but here’s an article on shielding of vent holes if you wanted a place to start your research
@JH - the dongle has the MCX coming out at right angles (not in one end, like the ProStick has).
The pigtail is c 6" long, MCX one end, with a 180 degree (i.e straight, rather than right-angled) bulk head SMA on the other end.
I’m not sure I understand your idea re using the bulkhead fixing on to the case?
Could I solder a wire between the body of the MCX connector on the pigtail, to a “clean” (i.e bare metal) point on the case?
Would a bit of copper “core” from another bit of coax do the trick?
For the new flight stick pro - I ordered these case (suggested by David Baker) rtl-sdr.com/buy-rtl-sdr-dvb-t-dongles/ RTL-SDR Blog Metal Case and Thermal Pad Upgrade
They are more expensive than your ebay shells but should require less modification.
You can use the heatsinks for the RPIs on the dongle ICs.
I think I have one on one of my dongles(they are all in cases). I ordered a bunch of heatsinks a few weeks ago.
What I mean is, assuming a female SMA connector on the end of your pigtail, just drill an appropriately sized hole in the plate on the end of the enclosure, stick the connector through and secure it with a nut. Similar to this manner:
The contact between the connector and the case should be more than sufficient to make the case a shield.
I mean, that’s basically what the uptronics amp does:
**EDIT: Ah I see, you got the smaller case. I clicked the top link quickly and assumed you had gotten the larger aluminum one. Yeah, you might want to soldier a wire between the MCX ground and the case or something. Not sure. **
As far as grounding goes I have taken apart my NooElec NESDR Mini+ Al’s and they are not grounded nor are there any sort of heat sinks present. I never had a problem with heat then again these have a TCXO clock… Aluminum cases are generally used to block interference such as RF other then that it is my experience they do nothing more so don’t drill it more than needed.
Update
Needed a break so took apart an old NooElec NESDR Mini? in an aluminum case sold to me as a NooElec NESDR Mini+ Al. I bought it on Amazon unknowingly at the time that some times you get things from sellers other than the one listed so it was not directly from NooElec. I should have cracked the case open when I first received it but didn’t… Anyways the two main parts are identical. This aluminum case I can confirm is the same used by the NooElec NESDR Mini+ Al’s I ordered direct. As you may or may not see the board sits in a slot and is not grounded at all nor are there any heat sinks present. I have run my true NooElec NESDR Mini+ Al’s months on end with no issues pertaining to cold or heat. As stated earlier the aluminum case is generally only good at being a RF shield nothing more.
The eagle-eyed among you (and anyone else who’s actually measured the dongle! ) will notice that that black case is actually about 0.5" too short for the dongle… lol
Whilst I certainly wouldn’t recommend getting the case I linked to, I’m sure I’ll find a use for it . (and hey, it was only like $2).
Had thought about getting a bigger one, but may just buy one from RTL-SDR.com, or NooElec.
Out of interest, mentioned this to my dad who’se more of an “old school electrical guy” than me, (though not directly radio-based), and he suggested making the USB plug itself “tight fit”, using that for grounding?
(My dad also said that soldering to anodised stuff’s a PITA).
Does it need to be part of the “antenna path”, or can it be any part of the board, on the basis that the entire thing is connected to the antenna path?
It is a good idea to make sure that both the SMA connector and the USB screen have a good electrical contact with the box. Grounding only the USB screen causes a severe degradation of the NF.
and
The SMA connector is connected to the case, but the USB shielding should NOT. It was done on purpose.
In the first video he connected the USB shielding to the case and figured it degraded the noise figure by 10dB then reverted it in the second video.
) will notice that that black case is actually about 0.5" too short for the dongle… lol