Damien Teney wrote:

Hello everybody,
I just finished my first homebrew radio, a VHF receiver with PLL, and it's
time to put it in a box ! I've often read that HF circuits should be put in
metal boxes, but I don't know which one should choose. Are "sealed"
enclosures such as this one
http://www.velleman.be/common/produc...?lan=1&id=7318
better than boxes like that one
http://www.velleman.be/common/produc...lan=1&id=11184 ?

And do you think that plastic and ABS boxes are really bad for HF circuits ?

Thanks for your answers !


Enclosures can cost you more than the whole rest of your project if
you're not careful.

The ideal box would be an aluminum or copper box, seamless, with no
holes. This would present problems with controlling your device,
getting power into it and signal out, so you have to make some compromises.

Depending on how sensitive your circuit is and how much RF it generates
you can go everywhere from no enclosure at all to a machined metal box.
For a VHF rig you probably want fairly good shielding.

For enclosures I go to hamfests and garage sales and buy old CB radios.
After I rip the guts out this gives me a good looking enclosure that's
designed for RF and costs way less than what a new one would.

Alternately you can make a really good, ugly enclosure by soldering
sections of unetched circuit board together -- see if there's a surplus
shop in your area that sells the stuff. I mount lids by soldering
sections of 1/8" brass tubing to the inside walls of my enclosure; you
can tap these to 4-40 and run a screw in them. Once you're done making
it work you can put it in a plastic box.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com