Simple, cheap, material for shielding
Many home brewers already know this, but there always seems to be a few that don't know.
When you need to use some sort of shielding between stages, the plain old "tin can" works great. Just remove the ends from the can, cut across the can (preferably at the seam), and then use "tin snips" to remove the bead on each side. Flatten out the metal by drawing across the edge of a table, piece of wood, etc. The metal is easy to work with using hand tools and takes solder very easily. Just cut to size, use something like the "hand seamers" described in another thread to form the edge of the material so that it can be machine screwed, soldered, etc., to the chassis, circuit board, etc.
Those cans with the flat sides work best although the corregated types can be used.
Sheet aluminum, galvanized iron, etc., of course, work well for shielding. However, those metals are becoming expensive and, in some areas, not that easy to find. Tin cans are, fortunately, very easy to find and, this is the best part, there is no cost for the material.
Good ideas never get old
You have good ideas, Glen. I used a tin can to shield plug in coils in my first regen receiver.
I use the shielding from old PC monitors. The CRT was often shielded with a very easy to use solid or perforated metal.
I used a piece to cover the PA compartment of a HB TX. I also have an active antenna in a gourmet coffee can.
The not for free examples:
Like many others, I also buy various plate and sheet aluminum a local scrap metal shops. By the pound and I can usually pick through the pile.
Home Depot and Lowe's used to carry a perforated aluminum material you could cut with scissors. Not strong for chassis but good enough to keep fingers out of some exposed breadboard rigs.
Aluminum pop cans are easier to work with.
TOM K8ERV Montrose Colo
Even aluminum foil pasted to cardboard would work.
I mostly use aluminum scotch tape (not the plastic one, which is impregnated by aluminum powder, but one made from real aluminum).
Aluminum gridmesh - see e.g.g here: http://is.gd/zbid2v
It's an alu sheet cut in a dash-pattern, then stretched to form diamond-shaped holes. Very easy to cut with metal sheet scissors, can be roughly bent on the edge of a table, retains shapes, more forgiving than solid sheet, can be bolted down to a chassis or onto itself with small bolts or screws through its holes, permits ventilation, you can use a drill and self tapping screws to add bolts later if you want to improve mating or if you stripped a screw seat and want another one.
I use it for building separate shielded compartments bolted on top of PCB or ugly construction boards inside a larger box.
- cutting it may form a spiky edge
- electrically as in other aluminum shields, mates well with other aluminum, OK with steel, not onto copper - unless tinned
- compared to tape or solid flat sheet it has lower capacitance on overlapping sections that don't mate well, so either it's bolted down or won't quasi-short by capacitive coupling.
Last edited by N1JPR; 08-09-2011 at 02:19 PM.
Some high end CRT 'puter' monitors are well screened with perforated aluminum, usually of generouse size, these are ideal for PA compartments etc.
Whilst on with materials. Never 'clod' any defunct LCD monitors out, three or four sheets of Mylar can be had when you strip the screens down... and usually good plastic sheets about a quarter inch thick that is used for screen backing.
Another perforated metal that is often used when ventilation is needed is "cane metal".
Attached is a photo of a "scrap" of such removed from the remains of an old project.
In large arias were RFI is a problem. You can buy a paint that is intended for children’s walls. It contains iron powder and is painted on walls so magnets can be placed on the wall. It works well were sensitive electronics are effected by RF or static can build up. It is slightly conductive when tested with a ohm meter and provides a fair to good rf shield. The last place I bought it was HWI hardware about 10 years ago. If I remember it was about $10 a quart then.