Quick, simple question:

Would a normal aluminum can be any good for RF shielding of a balun, or
would it for some reason not work? Should I connect it to ground?

And;
What does a transmatch do for me that a normal balun/transformer won't do
for me?

Thank you for your time.
Sincerecly,
--
Nosforit

Ceriel Nosforit wrote:
Quick, simple question:

Would a normal aluminum can be any good for RF shielding of a balun, or
would it for some reason not work? Should I connect it to ground?

And;
What does a transmatch do for me that a normal balun/transformer won't do
for me?

Thank you for your time.
Sincerecly,
Well IF cans are made of aluminum so I would think a can would work
fine. Normally one should keep the walls of the can some minimal
distance from the coil windings. IIRC the radius of the can should be
something like 2-3 times the dia. of the coil.

On Feb 2, 8:12 pm, ken scharf wrote:
Ceriel Nosforit wrote:
Quick, simple question:

Would a normal aluminum can be any good for RF shielding of a balun, or
would it for some reason not work? Should I connect it to ground?

And;
What does a transmatch do for me that a normal balun/transformer won't do
for me?

Thank you for your time.
Sincerecly,

Well IF cans are made of aluminum so I would think a can would work
fine. Normally one should keep the walls of the can some minimal
distance from the coil windings. IIRC the radius of the can should be
something like 2-3 times the dia. of the coil.


I believe that I've read that the distance from metallic objects
should, at a bare minimum, be at least 1/2 the coil diameter. So that
means 2 times minimum, giving 1/2 of coil diameter around the sides.
3 would be much better. Aluminum is good shielding material; onlt
thing better would be copper (or silver).

Alas, on the wretched hour of Fri, 02 Feb 2007 21:52:54 -0800 tack thusly
proclaimed:

snip

I believe that I've read that the distance from metallic objects
should, at a bare minimum, be at least 1/2 the coil diameter. So that
means 2 times minimum, giving 1/2 of coil diameter around the sides.
3 would be much better. Aluminum is good shielding material; onlt
thing better would be copper (or silver).

Guess I came up with a rather cheap alternative then.

Think newspaper, or any other kind of paper, would be good filling
material to isolate the transformer from the aluminum can?

--
Nos

There are two things to keep in mind when you put a coil in a can.

1. The inductance will decrease due to the reduced voulme for the
magnetic energy. This is the same effect as using a brass slug to
change teh inductance of a coil for VHF applications.
2. The losses will increase due to the induced currents in the walls
of the container.

The further away the walls are the lower the effect. The various rules
of thumb you hear are just the result of someone determining what is
acceptable.

73 de K9GXC, Jim

On Fri, 02 Feb 2007 13:45:47 GMT, "Ceriel Nosforit"
wrote:

Quick, simple question:

Would a normal aluminum can be any good for RF shielding of a balun, or
would it for some reason not work? Should I connect it to ground?

And;
What does a transmatch do for me that a normal balun/transformer won't do
for me?

Thank you for your time.
Sincerecly,

James M. Potter wrote:
There are two things to keep in mind when you put a coil in a can.

1. The inductance will decrease due to the reduced voulme for the
magnetic energy. This is the same effect as using a brass slug to
change teh inductance of a coil for VHF applications.
2. The losses will increase due to the induced currents in the walls
of the container.

What happens is that the metal acts as a shorted turn which absorbs some
of the current flowing in the inductor. A brass slug core inside the
coil takes advantage of this, the closer to the center of the coil the
greater the effect. The result is both a lowering of the inductance and
probably the Q. An effective way to tune vhf-uhf circuits, but a
shorted rotary turn was also used on the hf bands in "olden" days.
In the case of small tightly wound inductors with iron core slugs
the coupling from the shield can to the coil is rather small (ratio of
the turns and inductance) so the effect is small.

The further away the walls are the lower the effect. The various rules
of thumb you hear are just the result of someone determining what is
acceptable.

73 de K9GXC, Jim

On Fri, 02 Feb 2007 13:45:47 GMT, "Ceriel Nosforit"
wrote:

Quick, simple question:

Would a normal aluminum can be any good for RF shielding of a balun, or
would it for some reason not work? Should I connect it to ground?

And;
What does a transmatch do for me that a normal balun/transformer won't do
for me?

Thank you for your time.
Sincerecly,

Alas, on the wretched hour of Sat, 03 Feb 2007 08:29:40 -0700 James M.
Potter thusly proclaimed:

There are two things to keep in mind when you put a coil in a can.

1. The inductance will decrease due to the reduced voulme for the
magnetic energy. This is the same effect as using a brass slug to
change teh inductance of a coil for VHF applications.
2. The losses will increase due to the induced currents in the walls
of the container.

The further away the walls are the lower the effect. The various rules
of thumb you hear are just the result of someone determining what is
acceptable.

Ah, so if there's lots of noise where I put my transformer I'm better off
taking a small hit to signal strength to still improve my s/n ratio, but
if there's little noise I'd just be canceling out the weakest signals...
Guess I'll have to try it with and without the can then to see if I've got
lots of noise here.

Thanks for the reply.

--
Nos

On Sat, 03 Feb 2007 14:47:28 GMT, Ceriel Nosforit wrote:
Alas, on the wretched hour of Fri, 02 Feb 2007 21:52:54 -0800 tack thusly
proclaimed:

snip

I believe that I've read that the distance from metallic objects
should, at a bare minimum, be at least 1/2 the coil diameter. So that
means 2 times minimum, giving 1/2 of coil diameter around the sides.
3 would be much better. Aluminum is good shielding material; onlt
thing better would be copper (or silver).

Guess I came up with a rather cheap alternative then.

Think newspaper, or any other kind of paper, would be good filling
material to isolate the transformer from the aluminum can?

Until it absorbs moisture.....

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
*** Killfiling google posts: http://jonz.net/ng.htm

On Feb 3, 10:10 am, Allodoxaphobia wrote:
On Sat, 03 Feb 2007 14:47:28 GMT, Ceriel Nosforit wrote:
Alas, on the wretched hour of Fri, 02 Feb 2007 21:52:54 -0800 tack thusly
proclaimed:

snip

I believe that I've read that the distance from metallic objects
should, at a bare minimum, be at least 1/2 the coil diameter. So that
means 2 times minimum, giving 1/2 of coil diameter around the sides.
3 would be much better. Aluminum is good shielding material; onlt
thing better would be copper (or silver).

Guess I came up with a rather cheap alternative then.

Think newspaper, or any other kind of paper, would be good filling
material to isolate the transformer from the aluminum can?

Until it absorbs moisture.....

Jonesy
--
Marvin L Jones | jonz | W3DHJ | linux
38.24N 104.55W | @ config.com | Jonesy | OS/2
*** Killfiling google posts: http://jonz.net/ng.htm- Hide quoted text -

- Show quoted text -

Well, you saw what someone wrote: "The various rules
of thumb you hear are just the result of someone determining what is
acceptable . . .". Put your creation together and see what "is acceptable". If'n it ain't, then get a bigger can.