I wonder if there is any mileage to be had from adapting
the numerous junk-mail CD's as the vanes of ATU
capacitors?

1. We already have a form that is circular (no waste) and
with an accurately-positioned central hole.

2. There is a metallic film sandwiched between the plastic.

3. Is this film to thin to stand up to the RF currents that
will spread out across it when charging & discharging?

4. How would we make metallic contact to the film without
destroying the film at the point of contact?

5. Does anybody know the type of metal making up the film, i.e.,
can we solder to it?

6. Is the plastic of a suitable quality? Will it arc-through?

On Thu, 13 Jan 2005 13:09:02 -0000, "Airy R.Bean" wrote:

| I wonder if there is any mileage to be had from adapting
| the numerous junk-mail CD's as the vanes of ATU
| capacitors?

I make mine into Christmas decorations.
Stick in pairs using double sided foam pads, on monofilament fishing line.
Dangle a lot of these strings inside a window.

--
Dave Fawthrop dave hyphenologist co uk
Killfile and Anti Troll FAQs at
http://www.hyphenologist.co.uk/killfile.

On Thu, 13 Jan 2005 13:09:02 -0000, "Airy R.Bean"
wrote:

I wonder if there is any mileage to be had from adapting
the numerous junk-mail CD's as the vanes of ATU
capacitors?

1. We already have a form that is circular (no waste) and
with an accurately-positioned central hole.

2. There is a metallic film sandwiched between the plastic.

3. Is this film to thin to stand up to the RF currents that
will spread out across it when charging & discharging?

4. How would we make metallic contact to the film without
destroying the film at the point of contact?

5. Does anybody know the type of metal making up the film, i.e.,
can we solder to it?

6. Is the plastic of a suitable quality? Will it arc-through?

A little Googling would soon show you whether the critical factor,
which you doubtless have already determined from your preliminary
calculations is the loss tangent for the CD substrate, may well render
such a use as inadvisable.
--
from
Aero Spike

Airy R.Bean wrote:

I wonder if there is any mileage to be had from adapting
the numerous junk-mail CD's as the vanes of ATU
capacitors?

So you've given up on using them to make 30 line television systems then?

Do a web search about this - plenty of info - though you claim you don't
web search.

David.

"David Edmonds" wrote in message
...
Airy R.Bean wrote:

I wonder if there is any mileage to be had from adapting
the numerous junk-mail CD's as the vanes of ATU
capacitors?

So you've given up on using them to make 30 line television systems then?

Do a web search about this - plenty of info - though you claim you don't
web search.

Superficially the idea has some merit but you would have to machine the
discs anyway (they are totally symetrical and thus the area overlapping with
the fixed vanes wouldn't change). By the time you've machined then to be
asysmetric, might as well have made metal plates and avoid all the other
problems as well.

To problems in making variable Cs, the use of a CDROMs offers little.

Etching plates on PCB and using the fibre glass for the mechanical side is
maybe a better idea.

--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

Hardly - you have the cost of purchase and the inconvenience of
etching. Junk mail cd's are free issue.

"Brian Reay" wrote in message
...
Etching plates on PCB and using the fibre glass for the mechanical side is
maybe a better idea.

I wonder if there is any merit in using aluminum foil
duct tape to make a capacitor?
"Airy R.Bean" wrote in message
...
I wonder if there is any mileage to be had from adapting
the numerous junk-mail CD's as the vanes of ATU
capacitors?

1. We already have a form that is circular (no waste) and
with an accurately-positioned central hole.

2. There is a metallic film sandwiched between the plastic.

3. Is this film to thin to stand up to the RF currents that
will spread out across it when charging & discharging?

4. How would we make metallic contact to the film without
destroying the film at the point of contact?

5. Does anybody know the type of metal making up the film, i.e.,
can we solder to it?

6. Is the plastic of a suitable quality? Will it arc-through?

"Radio Man" wrote in message
news:SbyFd.20564$lG.19133@trnddc03...
I wonder if there is any merit in using aluminum foil
duct tape to make a capacitor?

I wonder what the background to you idea is?

New approaches to existing designs should offer one or more of:

Cost savings (cheaper materials, less man hours, ease of manufacture etc)
Better reliability and/or life (not the same thing by the way)
Extra functionality

For most things, the cost of materials is not a cost driver- the cost of the
material in a variable capacitor is dwarfed by the labour and machining
costs.

So, how does using duct tape help?

The CD idea falls flat as, while they may be cheap, the amount of machining
'saved' is mininmal. I suppose if you are totally strapped for cash, out of
work and with time on your hands, they may offer some advantage, but you
end up with a 'product' of inferior quality. Engineers who are driven by
such a penny pinching approach usually end up bankrupting their company as
their products are poor.


--
Brian Reay
www.g8osn.org.uk
www.amateurradiotraining.org.uk
FP#898

"Machining"? What, cutting with a pair of scissors?

There's considerably more machining involved in your
proposal to use etched PCB.

"Brian Reay" wrote in message
...
The CD idea falls flat as, while they may be cheap, the amount of
machining
'saved' is mininmal. I

The proposal to investigate the use of junk-mail CD's
seems to meet your very first criterion.

"Brian Reay" wrote in message
...
New approaches to existing designs should offer one or more of:

Cost savings (cheaper materials, less man hours, ease of manufacture etc)