Shutting the RPi down - RF leakage

Discussion about this major DATV Project. See https://wiki.batc.org.uk/The_Portsdown_Transmitter
radiogareth
Posts: 1211
Joined: Wed Jan 06, 2016 9:46 am

Shutting the RPi down - RF leakage

Post by radiogareth » Sun May 15, 2022 2:54 pm

Yesterday my talkback on 144.750 was disrupted by interference from the Raspberry Pi, admittedly running inside a plastic box. I have not previously noticed this issue - possibly as incoming signals were loud enough....
Electrolube used to supply (Farnell showing as not available but others still have it at around £30 a tin) a nickel spray (not cheap, even back in a1986 when I sprayed the insides of 5 BBC-B computer cases) so I'm wondering if there are alternatives.
This seems suitable, https://uk.farnell.com/ambersil/6190011 ... dp/1676599 but before I commit, has anyone tried it for RF screening purposes? Its half the price of the electrolube nickel stuff....
Gareth

G1BVI
Posts: 282
Joined: Wed Aug 02, 2017 7:32 am

Re: Shutting the RPi down - RF leakage

Post by G1BVI » Sun May 15, 2022 3:01 pm

I use a RS 220 6233 to prevent this happening.
73

Nick

radiogareth
Posts: 1211
Joined: Wed Jan 06, 2016 9:46 am

Re: Shutting the RPi down - RF leakage

Post by radiogareth » Sun May 15, 2022 3:04 pm

Thanks Nick, not an option for my (finished build, its got too much hooked up to it and case space is minimal. From memory I had to shorten the supplied screen stand-offs to get it onto the screen back and put the lid on....
Thanks anyway...

Gareth

G1BVI
Posts: 282
Joined: Wed Aug 02, 2017 7:32 am

Re: Shutting the RPi down - RF leakage

Post by G1BVI » Sun May 15, 2022 3:37 pm

I have a portadown in a plastic case and that knocks out my qrp labs GPS rx which uses an internal antenna.
I remember rhe bbcb days tim foil used then.
These days I would try copper tape which you can buy in reels.
It is self adhesive and very effective.
I use it to patch up exit entry holes when using an emc chamber
N

radiogareth
Posts: 1211
Joined: Wed Jan 06, 2016 9:46 am

Re: Shutting the RPi down - RF leakage

Post by radiogareth » Sun May 15, 2022 3:44 pm

Worth a try at least on the bits I can get at - new build underway in a rectangular box, that will be easier.....

Just realised that I have the same QRP-Labs clock with occasional 'outages'....my shack PD4 is on the bench RIGHT NEXT TO IT......but not always on...mystery solved. It must radiate like, well, something that radiates...

Gareth

G1BVI
Posts: 282
Joined: Wed Aug 02, 2017 7:32 am

Re: Shutting the RPi down - RF leakage

Post by G1BVI » Sun May 15, 2022 4:06 pm

;) well the tape works so hope you can get some in.
My clock is inside and not too close to a window.

When I first noticed it I saw it was a cloudy damp day so moved it closer to the window..
It did lock up.
I think it must depend upon the field strength which varies with climate.
Not bothered to check it on my analyser but might look one day
73 and good luck

Nick

radiogareth
Posts: 1211
Joined: Wed Jan 06, 2016 9:46 am

Re: Shutting the RPi down - RF leakage

Post by radiogareth » Sun May 15, 2022 4:31 pm

Found this too, https://www.screwfix.com/p/no-nonsense- ... 00ml/40801 having looked inside box its got so many mounting bumps its going to be a mess to try and copper-tape it.
Research continuing....the old Electrlube stuff has been replaced by a -P version that doesn't stick as well, according to the forums. And its expensive!
Gareth

G1BVI
Posts: 282
Joined: Wed Aug 02, 2017 7:32 am

Re: Shutting the RPi down - RF leakage

Post by G1BVI » Sun May 15, 2022 4:41 pm

You would also need to make sure surface is keyed very well before application which it sounds likely to be tricky......

Good luck

N

g4eml
Posts: 666
Joined: Thu Apr 26, 2018 9:36 am

Re: Shutting the RPi down - RF leakage

Post by g4eml » Sun May 15, 2022 4:43 pm

Farnell stock the MG Chemicals ‘SuperShield’ Nickel spray. Stock no 2811914

As you say, it is expensive but does a good job. The resistivity of the film created is very low, only a few ohms per square. I used it to spray the plastic box of one of my Langstones, and it helped a lot. It sticks very well. I also used it when making my copper plated reflectors for 122GHz.

Colin G4EML.

g8gtz
Posts: 1732
Joined: Wed Apr 07, 2010 6:26 pm

Re: Shutting the RPi down - RF leakage

Post by g8gtz » Sun May 15, 2022 9:54 pm

Similar thread here:

viewtopic.php?f=15&t=7480&p=28078#p28078

I used one of the metal case/heatsink and coated the rear of the plastic screen box in aluminium tape which does reduce radiation but does not completely remove it and so ended up putting the Pi in a diecast box with a metal grille lid to let the heat out.

Doesn't completely cure it as some radiation is from the front of the screen and some menu pages which have a lot of bright content are worse than others, but it is now at acceptable levels.

Noel

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