2.4GHz absorption by plastics

[martin griffith]

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

 

[Tim Williams]

Duh, put it in the microwave and see if it melts. ;-)

Offhand, polypropylene Gladware containers are microwave rated.

Tim

 

[martin griffith]

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

 

[Vladimir Vassilevsky]

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

 

[PeterD]

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.

 

[martin griffith]

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

 

[Jim Yanik]

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?

 

[Jeff Liebermann]

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 <mart_in_medina@ya___.es> seems to suggest
Medina, Spain. Dunno.

 

[James Beck]

The munged email address <mart_in_medina@ya___.es> seems to suggest
Medina, Spain. Dunno.

Well, now is the time to buy one and write it off as an R&D expense

 

[Rich Grise]

.

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

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

Cheers!
Rich

 

[Rich Grise]

[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

 

[martin griffith]

The munged email address <mart_in_medina@ya___.es> seems to suggest
Medina, Spain. Dunno.

In a little white village
http://www.flickr.com/photos/11988582@N00/

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


martin

 

[Fred_Bartoli]

martin griffith a écrit :

In a little white village
http://www.flickr.com/photos/11988582@N00/

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

There're some nice pics...
and you have a good eye

 

[Jim Yanik]

In a little white village
http://www.flickr.com/photos/11988582@N00/

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


martin

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.

 

[LVMarc]

In a little white village
http://www.flickr.com/photos/11988582@N00/

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

 

[Spehro Pefhany]

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.

I see a 600W Sharp that can take a dinner plate and is only 13" wide
(a 13" cube in fact):

http://www.theapplecollection.com/iMac/iStore/HalfPintSplash.html


Best regards,
Spehro Pefhany

 

[martin griffith]

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

 

[martin griffith]

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

 

[Rich Grise]

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

 

[martin griffith]

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