RF Prototyping on a Shoe Box

Kevin · Jun 12, 2005

http://www.wd5gnr.com/foil.htm

Hi all,
I saw this good site that shows how to prototype RF gear on a show box using
copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Cheers,
Kevin.

Joerg · Jun 12, 2005

Hello Kevin,

I saw this good site that shows how to prototype RF gear on a show box using
copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Then something gets hot, the shoe box lid catches fire, the carpet
lights up, sirens start blaring ...

Regards, Joerg

http://www.analogconsultants.com

Kevin · Jun 12, 2005

You could also use Plexi Glass or timber.
That should keep the Firemen at bay!!
Kevin.
"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message
news:l92re.260$Pa5.25@newssvr21.news.prodigy.com...

Hello Kevin,

I saw this good site that shows how to prototype RF gear on a show box
using copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Then something gets hot, the shoe box lid catches fire, the carpet lights
up, sirens start blaring ...

Regards, Joerg

http://www.analogconsultants.com

Joerg · Jun 12, 2005

Hello Kevin,

You could also use Plexi Glass or timber.

Dry timber is pretty flammable. I wouldn't use plastics either, you
never know how toxic its fumes can be.

Regards, Joerg

http://www.analogconsultants.com

Jim Thompson · Jun 12, 2005

On Sun, 12 Jun 2005 21:53:21 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Kevin,

I saw this good site that shows how to prototype RF gear on a show box using
copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Then something gets hot, the shoe box lid catches fire, the carpet
lights up, sirens start blaring ...

Regards, Joerg

http://www.analogconsultants.com

About 20 years ago I sent the two sons out into the side yard to dig
out a Palo Verde stump.

About an hour later I hear sirens... seemed awfully close.

I go outside to find that the sons thought they could "accelerate" the
process with a little gasoline.

Fire truck pulls up and thoroughly soaks the stump, so they still had
to dig it out.

The fire captain is about to cite the sons for unlawful burning when
the mayor (and neighbor) pulls up. (Drinkwater, for those Arizonans
lurking here.)

He convinces fire captain not to cite.

The wonders of the past when we were a small town ;-)

...Jim Thompson
--
| James E.Thompson, P.E. | mens |
| Analog Innovations, Inc. | et |
| Analog/Mixed-Signal ASIC's and Discrete Systems | manus |
| Phoenix, Arizona Voice

480)460-2350 | |
| E-mail Address at Website Fax

SioL · Jun 12, 2005

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message news:mx2re.257$NU5.85@newssvr13.news.prodigy.com...

Hello Kevin,

You could also use Plexi Glass or timber.

Dry timber is pretty flammable. I wouldn't use plastics either, you never know how toxic its fumes can be.

Plexi burns like hell once it really gets going, nasty fumes as well.

--
Siol
------------------------------------------------
Rather than a heartless beep
Or a rude error message,
See these simple words: "File not found."

Joerg · Jun 12, 2005

Hello SioL,

Plexi burns like hell once it really gets going, nasty fumes as well.

Yes, and I still remember all the people who died at Duesseldorf airport
in Germany. Not from the fire itself but from toxic fumes.

Regards, Joerg

http://www.analogconsultants.com

Robert · Jun 12, 2005

"Kevin" <irishdude79@REMOVEyahoo.ie> wrote in message
news:hw1re.1106$R5.277@news.indigo.ie...

http://www.wd5gnr.com/foil.htm

Hi all,
I saw this good site that shows how to prototype RF gear on a show box
using copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Cheers,
Kevin.

I like Jim William's AN47-1 App Note at Linear Technology on building high
speed circuits.

Go to www.linear.com and use the upper right "Search" box for AN47-1. It's
chock full of tips and gotchas for building high speed circuitry. But the
note's pretty big. I wouldn't try downloading it on dial-up.

He does it on copper clad pc board with what he calls "ugly breadboard"
techniques to minimize parasitics. IIRC, he's got 100MHz Amplifier circuits
in the note with very clean results. Though his pictures and data tend to be
in the Time Domain. He's also got a nice pulse generator circuit in an
Appendix for generating about a 10V 200ps rise and fall time pulse to test
these circuits. Another appendix has the "ABC's of Probes" guest written by
the Tektronix folks.

One caveat, the note's pretty old and doesn't talk much about SMD
components.

Robert

Jim Thompson · Jun 12, 2005

On Mon, 13 Jun 2005 00:36:56 GMT, "Robert" <Robert@yahoo.com> wrote:

"Kevin" <irishdude79@REMOVEyahoo.ie> wrote in message
news:hw1re.1106$R5.277@news.indigo.ie...
http://www.wd5gnr.com/foil.htm

Hi all,
I saw this good site that shows how to prototype RF gear on a show box
using copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Cheers,
Kevin.

I like Jim William's AN47-1 App Note at Linear Technology on building high
speed circuits.

Go to www.linear.com and use the upper right "Search" box for AN47-1. It's
chock full of tips and gotchas for building high speed circuitry. But the
note's pretty big. I wouldn't try downloading it on dial-up.

[snip]

480)460-2350 | |
| E-mail Address at Website Fax

Robert · Jun 13, 2005

"Jim Thompson" <thegreatone@example.com> wrote in message
news:rklpa1d4ibs8ps8asvvdspaqiu7p8f89ui@4ax.com...

On Mon, 13 Jun 2005 00:36:56 GMT, "Robert" <Robert@yahoo.com> wrote:
"Kevin" <irishdude79@REMOVEyahoo.ie> wrote in message
Hi all,
I saw this good site that shows how to prototype RF gear on a show box
using copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Cheers,
Kevin.

I like Jim William's AN47-1 App Note at Linear Technology on building high
speed circuits.

Go to www.linear.com and use the upper right "Search" box for AN47-1. It's
chock full of tips and gotchas for building high speed circuitry. But the
note's pretty big. I wouldn't try downloading it on dial-up.

[snip]

2 seconds on Cox ;-)

...Jim Thompson

Wouldn't know. I got it in a paper copy a long time ago.

What do you think of the App Note? Have you seen it?

Robert

ehsjr · Jun 13, 2005

Kevin wrote:

http://www.wd5gnr.com/foil.htm

Hi all,
I saw this good site that shows how to prototype RF gear on a show box using
copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Cheers,
Kevin.

You'll forget shoe box construction once you try

"Manhattan Construction". Go to:
http://www.e-discounter.net/qrparci/messages/6365.html
and scroll down to see what it looks like.
Refer to:
http://www.k7qo.net/manhattan.pdf
for details on how to do it. It is easier than foil on
shoebox, and far better. You have a ground plane under
100% of the circuit.

Ed

Barry Lennox · Jun 12, 2005

On Sun, 12 Jun 2005 22:18:58 GMT, Joerg
<notthisjoergsch@removethispacbell.net> wrote:

Hello Kevin,

You could also use Plexi Glass or timber.

Dry timber is pretty flammable. I wouldn't use plastics either, you
never know how toxic its fumes can be.

Regards, Joerg

Agreed, timber and plastics are nasty substances in a burn-up, so I'd
use an old dinner plate, the local goodwill shop sells them for $2 a
bagful. Ceramic, copper, solder, all the makings of a quality low-loss
construction, much like Tek used to use in their real quality scopes ?

The only down-side I can think of would be dropping it!

Barry Lennox

Dave · Jun 13, 2005

Kevin wrote:

http://www.wd5gnr.com/foil.htm

Hi all,
I saw this good site that shows how to prototype RF gear on a show box using
copper tape.
Better than spending a day designing a pcb board only to have to make
adjustments when its too late.

Cheers,
Kevin.

It does not provide a ground plane though, so radiation must be pretty

high. It is not something I would do.

I prefer what I call 'dead bug sytle' where I cut bits of single sided
PCB up, and stick those on top of another bit of singled side PBB. You
can make 50 Ohm tracks, by making the widths right.

RF is not quite well as contrained as on a normal board, since there is
no dieletric outside the track.

To be more precise, etch simple stright lines on PCB, and make the
dielectric 3 x the track width or something. Just stick to lumps of that
and pads. I've used this at several hundred MHz.

Anno Siegel · Jun 13, 2005

Joerg <notthisjoergsch@removethispacbell.net> wrote in sci.electronics.design:

Hello SioL,

Plexi burns like hell once it really gets going, nasty fumes as well.

Yes, and I still remember all the people who died at Duesseldorf airport
in Germany. Not from the fire itself but from toxic fumes.

That was PVC (Polyvinyl chloride) with its nasty HCl fumes. Plexi is
acrylic something. The fumes are probably no fun either, but they don't
have the poison-gas quality of smoldering PVC.

Anno

Joerg · Jun 13, 2005

Hello Jim,

2 seconds on Cox ;-)

Wow. It was about 15sec on SBC DSL. It's a 5MB document, so with all
overhead that would mean your BW is around 25Mbps?

I really like that classic Tek scope in Fig 31.

Regards, Joerg

http://www.analogconsultants.com

Joerg · Jun 13, 2005

Hello Ed,

You'll forget shoe box construction once you try
"Manhattan Construction". Go to:
http://www.e-discounter.net/qrparci/messages/6365.html
and scroll down to see what it looks like.
Refer to:
http://www.k7qo.net/manhattan.pdf
for details on how to do it. It is easier than foil on
shoebox, and far better. You have a ground plane under
100% of the circuit.

That's the way to go but it is an old trick. We did that in the 80's,
except that the pads weren't round but usually squares. Easier to cut.

Wainwright makes little strips that can be glued on, including SMT pads.
The only downside is that the peel-and-stick technique isn't too
reliable on really hot summer days when prototyping outside. When it
reaches 100F stuff can start to slide before you got some ground wires
soldered to it. So I either add some real glue or use my own squares.

Regards, Joerg

http://www.analogconsultants.com

Larry Brasfield · Jun 13, 2005

"Joerg" <notthisjoergsch@removethispacbell.net> wrote in message news:Qepre.636$NU5.198@newssvr13.news.prodigy.com...

Hello Ed,

You'll forget shoe box construction once you try
"Manhattan Construction". Go to:
http://www.e-discounter.net/qrparci/messages/6365.html
and scroll down to see what it looks like.
Refer to:
http://www.k7qo.net/manhattan.pdf
for details on how to do it. It is easier than foil on
shoebox, and far better. You have a ground plane under
100% of the circuit.

That's the way to go but it is an old trick. We did that in the 80's, except that the pads weren't round but usually squares.
Easier to cut.

Wainwright makes little strips that can be glued on, including SMT pads. The only downside is that the peel-and-stick technique
isn't too reliable on really hot summer days when prototyping outside. When it reaches 100F stuff can start to slide before you
got some ground wires soldered to it. So I either add some real glue or use my own squares.

Hi, Joerg.

At one startup I worked for, we had a little hand tool in
the lab to cut small isolated pads in a copper clad sheet.
Most of the copper was ground plane, of course. It
worked great when common transistor packages were
larger. Anymore, I think inexpensive etched prototypes
are the way to go. It's very difficult to build stuff by hand
as small as it can be when layed out on a regular PCB.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

Roger Johansson · Jun 14, 2005

Larry Brasfield wrote:

At one startup I worked for, we had a little hand tool in
the lab to cut small isolated pads in a copper clad sheet.

I have made several such tools.

Take an old screwdriver, use a file to change the blade into two sharp
points.
Like a straight fork.
Make one of the points a little softer and 1 mm shorter than the other.
Cut away material on one side of the rounded point so it becomes a
cutting edge.

This means that we need to think through the function.
Put the halfmade tool vertically on a piece of pcb board.
Turn the tool, see how the longer point digs into the copper and into
the pcb material under it.
So its position stays fixed.
The soft point will just glide around in a circle around the sharp
point.

We need to remove material from the soft point to create a flat
surface perpendicular to the movement, on one side of the soft point,
the side which is leading when the tool is turned clockwise.

When that side presents a flat vertical area it will cut away copper
easily. It can be made slightly spoon-shaped with a rotating minidrill
tool. Keep the edges of this flat or spoonshaped area sharp.

I use two different sizes, one for 3mm pads, one for 6mm.

Most of the copper was ground plane, of course. It
worked great when common transistor packages were
larger. Anymore, I think inexpensive etched prototypes
are the way to go. It's very difficult to build stuff by hand
as small as it can be when layed out on a regular PCB.

Why worry about space?

The board will be inside a box if it is in use, so the pcb design or
size are of very little significance.

In fact, it is a great advantage to have a fairly open circuit where
there is space enough for changes and repairs.

Use simple pcb laminate, single or doublesided, which is very cheap
when you find it in a surplus shop.
A lifetime supply can cost 20 dollars or so.

Then just cut suitable pieces, clean it with a kitchen sponge, groove
it with a sharp tool, to get the number of pads you think you need.

Start building, and you can add the methods from manhattan and dead bug
style, and make new pads with the rotating tool we made above.

If you need a groundplane, or if you want to build on both sides, use
doublesided pcb laminate.

Basically you need no holes, which saves a lot of work. Old components
can easily be soldered to a flat surface with some ingenuity, cut
wires, bend wires, and solder. New smd components are placed over a
groove and soldered at both sides.

Integrated smd circuits are a problem, because of the many pins tightly
packed, but that is a problem with most simple building methods, and
can only be fully solved by designing and etching your own circuit
boards.

--
Roger J.

Larry Brasfield · Jun 14, 2005

"Roger Johansson" <no-email@no.invalid> wrote in message
news:xn0e3h8jhh896rk000@news.sunsite.dk...

Larry Brasfield wrote:

At one startup I worked for, we had a little hand tool in
the lab to cut small isolated pads in a copper clad sheet.

I have made several such tools.

Take an old screwdriver, use a file to change the blade into two sharp
points.
Like a straight fork.
Make one of the points a little softer and 1 mm shorter than the other.
Cut away material on one side of the rounded point so it becomes a
cutting edge.

This means that we need to think through the function.
Put the halfmade tool vertically on a piece of pcb board.
Turn the tool, see how the longer point digs into the copper and into
the pcb material under it.
So its position stays fixed.
The soft point will just glide around in a circle around the sharp
point.

We need to remove material from the soft point to create a flat
surface perpendicular to the movement, on one side of the soft point,
the side which is leading when the tool is turned clockwise.

When that side presents a flat vertical area it will cut away copper
easily. It can be made slightly spoon-shaped with a rotating minidrill
tool. Keep the edges of this flat or spoonshaped area sharp.

I use two different sizes, one for 3mm pads, one for 6mm.

That looks pretty doable. The only think I dislike about
homemade cutting tools is that they dull fast. (Maybe a
foray into the art of tempering would fix that.)

Most of the copper was ground plane, of course. It
worked great when common transistor packages were
larger. Anymore, I think inexpensive etched prototypes
are the way to go. It's very difficult to build stuff by hand
as small as it can be when layed out on a regular PCB.

Why worry about space?

The board will be inside a box if it is in use, so the pcb design or
size are of very little significance.

In fact, it is a great advantage to have a fairly open circuit where
there is space enough for changes and repairs.

For some kinds of RF, a circuit you can get your fingers
or hands into can still work. For other kinds, the added
stray inductance and capacitance that follows from size
will make the prototype a poor predictor of performance
obtainable once a PCB is carefully layed out and built.

Use simple pcb laminate, single or doublesided, which is very cheap
when you find it in a surplus shop.
A lifetime supply can cost 20 dollars or so.

Then just cut suitable pieces, clean it with a kitchen sponge, groove
it with a sharp tool, to get the number of pads you think you need.

Start building, and you can add the methods from manhattan and dead bug
style, and make new pads with the rotating tool we made above.

If you need a groundplane, or if you want to build on both sides, use
doublesided pcb laminate.

I've always liked the ground plane on the component
side where short connections can be made to it without
having to drill holes. That's what I like about the method
using isolated pads made where needed.

Basically you need no holes, which saves a lot of work. Old components
can easily be soldered to a flat surface with some ingenuity, cut
wires, bend wires, and solder. New smd components are placed over a
groove and soldered at both sides.

Integrated smd circuits are a problem, because of the many pins tightly
packed, but that is a problem with most simple building methods, and
can only be fully solved by designing and etching your own circuit
boards.

More true than ever as densities have gone up.

--
--Larry Brasfield
email: donotspam_larry_brasfield@hotmail.com
Above views may belong only to me.

Rene Tschaggelar · Jun 14, 2005

Robert wrote:

I like Jim William's AN47-1 App Note at Linear Technology on building high
speed circuits.

One caveat, the note's pretty old and doesn't talk much about SMD
components.

SMD are much better as they are much smaller.

Rene
--
Ing.Buero R.Tschaggelar - http://www.ibrtses.com
& commercial newsgroups - http://www.talkto.net

RF Prototyping on a Shoe Box

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