Maker Pro
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2.4GHz absorption by plastics

M

martin griffith

Jan 1, 1970
0
I've tried Mr Google, but I cant seem to find any tables about how bad
plastics are at absorbing RF.

For fun, I'm just about to make Jason Heckers' helix antenna
http://www.wlan.org.uk/jhecker.html

Any links?


martin
 
T

Tim Williams

Jan 1, 1970
0
Duh, put it in the microwave and see if it melts. ;-)

Offhand, polypropylene Gladware containers are microwave rated.

Tim
 
M

martin griffith

Jan 1, 1970
0
Duh, put it in the microwave and see if it melts. ;-)

Offhand, polypropylene Gladware containers are microwave rated.

Tim
Yeah I know the microwave trick, but I never intend buying one.

thanks for the polypropylene pointer


martin
 
V

Vladimir Vassilevsky

Jan 1, 1970
0
martin said:
I've tried Mr Google, but I cant seem to find any tables about how bad
plastics are at absorbing RF.
For fun, I'm just about to make Jason Heckers' helix antenna
http://www.wlan.org.uk/jhecker.html

Check any reference book on electric materials. PVC is one of the most
lossy. Polyethylene and teflon are the best. However it should not be
very important for that antenna.

Vladimir Vassilevsky

DSP and Mixed Signal Design Consultant

http://www.abvolt.com
 
P

PeterD

Jan 1, 1970
0
I've tried Mr Google, but I cant seem to find any tables about how bad
plastics are at absorbing RF.

For fun, I'm just about to make Jason Heckers' helix antenna
http://www.wlan.org.uk/jhecker.html

Any links?


martin

Put your plastic in a microwave oven. Nuke it for about 20 seconds. Is
it warm? Then it absorbs microwaves. If cool (it probably will be)
then it doesn't.
 
M

martin griffith

Jan 1, 1970
0
Put your plastic in a microwave oven. Nuke it for about 20 seconds. Is
it warm? Then it absorbs microwaves. If cool (it probably will be)
then it doesn't.

none of my neighbours have microwave ovens, neither do I :( or maybe
:(


martin
 
J

Jim Yanik

Jan 1, 1970
0
none of my neighbours have microwave ovens, neither do I :( or maybe
:(


martin

YOWZA..nothing like staying back in the Stone Age. ;-)
I've had the same MW for almost 30 years.

WHERE do you live?
 
J

Jeff Liebermann

Jan 1, 1970
0
YOWZA..nothing like staying back in the Stone Age. ;-)
I've had the same MW for almost 30 years.
WHERE do you live?

The munged email address <[email protected]___.es> seems to suggest
Medina, Spain. Dunno.
 
R

Rich Grise

Jan 1, 1970
0
.
none of my neighbours have microwave ovens, neither do I :( or maybe
:(

Good grief! What planet do you live on? ;-)

Cheers!
Rich
 
R

Rich Grise

Jan 1, 1970
0
[email protected] says...
Well, now is the time to buy one and write it off as an R&D expense :)

These days you don't even have to buy one - you can find them in
dumpsters, and they usually only need a fuse. (I've re-fused [no
pun intended] ovens that then lasted another 5 years.)

But I'd say if the original uses PVC, then PVC must be good enough. :)

Good Luck!
Rich
 
L

LVMarc

Jan 1, 1970
0
martin said:
In a little white village
http://www.flickr.com/photos/[email protected]/

The kitchen is so small, there isnt enough space to put a MW !


martin


most plastics avsrob very little em energy, this is related to the
dissaptaion factor for a given material.

for a raidted wave, the relfection loss, obtsined from going from air to
plastic, then plastic to air, gives a reflection loss .. this is an
order of magnitude or greater thsn dissaption factor for ost plasics.
the refletion losses are relate to eR the dilectric constant for the
material.. if you want more loss...l add little rsitors on a wave space
level to the material to increase losses. to decrease losses add....air
:) good luck and Best Regards,

Marc popek
 
M

martin griffith

Jan 1, 1970
0
they make some pretty small MW ovens these days.
In my Indy apartment,I kept the MW on top of the refrigerator.
And it's a full-size oven,not a sandwich-size model.

Ah, Spanish kitchens, the bastard architects only put two accesable
power sockets in as well. Phone lines and TV distro in each room, but
not in the kitchen!

I am a bit too old to change my cooking habits, ( a monster wok) and
I'd rather put the money towards a new scope, and a new flint for the
soldering iron


martin
 
M

martin griffith

Jan 1, 1970
0
martin griffith wrote: snip

most plastics avsrob very little em energy, this is related to the
dissaptaion factor for a given material.

for a raidted wave, the relfection loss, obtsined from going from air to
plastic, then plastic to air, gives a reflection loss .. this is an
order of magnitude or greater thsn dissaption factor for ost plasics.
the refletion losses are relate to eR the dilectric constant for the
material.. if you want more loss...l add little rsitors on a wave space
level to the material to increase losses. to decrease losses add....air
:) good luck and Best Regards,

Marc popek

Thanks, I think I spotted a VSWR meter circuit for 2.4G somewhere,
might be worth investigating


martin
 
R

Rich Grise

Jan 1, 1970
0
On 18 Jul 2007 17:19:45 GMT, in sci.electronics.design Jim Yanik
I am a bit too old to change my cooking habits, ( a monster wok) and
I'd rather put the money towards a new scope, and a new flint for the
soldering iron

So take a piece of the plastic you want to test to the microwave oven
store and ask for a demo. ;-)

(Or, just use the same PVC as the guy who wrote the page did.)

Good Luck!
Rich
 
M

martin griffith

Jan 1, 1970
0
So take a piece of the plastic you want to test to the microwave oven
store and ask for a demo. ;-)

(Or, just use the same PVC as the guy who wrote the page did.)

Good Luck!
Rich
Ok. I'll quit moaning :)


martin
 
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