Hello all

I've been doing a fair bit of internet reading about RF construction
projects. I'm still confused about something.

Most authors, including those in the ARRL Handbook, seem to espouse
"ugly construction" and a variant called Manhatten construction. I
understand that the reason is that these techniques minimize
capacitance by providing a large ground plane. Ugly construction seems
to also encompass perfboard construction with wire traces or direct
component-to-component connections. This seems to me to be not much
better than using pre-printed boards whose traces match, in geometry,
those of solderless prototyping boards.

I do understand that the solderless boards are inadequate for RF work,
but are the pre-printed perforated "protoboards" also inadequate.

Call it an OC tendency, but ugly construction is, well, ugly. Of
course, I want to use the best techniques for what I'm doing, and if UC
is the way to go, then that's what I'll do.

I'd appreciate your opinions on this.

Thanks
Basil B.

Basil B. wrote:

Hello all

I've been doing a fair bit of internet reading about RF construction
projects. I'm still confused about something.

Most authors, including those in the ARRL Handbook, seem to espouse
"ugly construction" and a variant called Manhatten construction. I
understand that the reason is that these techniques minimize
capacitance by providing a large ground plane. Ugly construction seems
to also encompass perfboard construction with wire traces or direct
component-to-component connections. This seems to me to be not much
better than using pre-printed boards whose traces match, in geometry,
those of solderless prototyping boards.

I do understand that the solderless boards are inadequate for RF work,
but are the pre-printed perforated "protoboards" also inadequate.

Call it an OC tendency, but ugly construction is, well, ugly. Of
course, I want to use the best techniques for what I'm doing, and if UC
is the way to go, then that's what I'll do.

I'd appreciate your opinions on this.

Thanks
Basil B.

I think the primary reason that folks espouse ugly construction is that
it may look bad to us, but the electrons like it just fine. It can be
tough to get over the aesthetics (or lack thereof) of your fine new
circuit, but it'll work just as well and it'll be less work than using a
PC board.

You can, of course, make a PC board. Unless you know _exactly_ what
you're doing you'll end up making mistakes, which will require changes,
which you won't get right the first time. So if you have your new,
flawed, PC board you'll modify it, and the mods will be, well, ugly.

So if you're going to make something ugly anyway, why not make it ugly
to start? Once it works right then you can make a nice pretty PC if you
feel like it.

--

Tim Wescott
Wescott Design Services
http://www.wescottdesign.com

Well, that is certainly a vote for UC. Do you also have an opinion of
the other idea, using pre-patterned, pre-etched boards such as
Veroboard and the like?

Thanks
Basil Burgess

Well, that is certainly a vote for UC. Do you also have an opinion of
the other idea, using pre-patterned, pre-etched boards such as
Veroboard and the like?

My own feeling, for what it's worth, is that these are pretty good for
DC and audio-frequency projects, but can have problems at RF.

A big part of the issue is one of grounding. Many of the pre-etched
proto boards I've seen use most of their real estate for pads and
pad-connection strips. There are usually sets of traces for supplying
power and ground to the components, but these don't use more than a
relatively small amount of the board's copper area and are often
run as long strips coming in from the side of the board.

As a result, if you have two groups of components which are physically
fairly close together, and connect components in these groups to the
physically-closest ground pads/strips (minimizing the lead length),
you may find that there are actually quite a few inches of PC-board
ground trace between one component's "grounded" lead and another.

This is usually adequate at DC and audio frequency. At RF, the
parasitic inductance of those long looping ground traces can have an
adverse effect on the circuit's stability. You can sometimes minimize
this by using a star-grounding approach, but since the connection pads
are pre-etched into clusters and strips there's likely to be a limit
to the number of components that you can connect to a "single point"
ground, and it may not be all that good an approximation of a true
single-point.

One of the recipes for making stable, friendly, and reproducible
designs at RF seems to be to minimize the impact of parasitic
reactances. As you point out, using "ugly" construction of the
Manhattan or free-air (point-to-point) variety minimizes parasitic
capacitance between components, and between components and the board.

It also has the benefit of minimizing parasitic _inductive_ reactance
in the circuit's "ground", if you use a solid copper ground plane as
the basis for your construction. "Ground" is always an
approximation... a perfect ground cannot be achieved at either DC or
RF... but you can get closer if you have lots of copper area to work
with.

Etched PC boards can be used quite successfully for RF projects, of
course, and often are. It's important, when laying out such a board,
to minimize unwanted parasitics... leaving large sections of un-etched
copper for grounding, using wide traces, paying attention to where the
actual ground currents flow, adding ground-shield traces between any
signal-carrying traces that might tend to suffer from cross-coupling,
and so forth.

One usually does not have the luxury of being able to take advantage
of these techniques (at least to their fullest) when using a
pre-etched proto board,

--
Dave Platt AE6EO
Hosting the Jade Warrior home page: http://www.radagast.org/jade-warrior
I do _not_ wish to receive unsolicited commercial email, and I will
boycott any company which has the gall to send me such ads!

It's much easier to make a sensitive RF circuit work with "ugly"
construction than on a typical PC board. There are a couple of reasons.
One is that leads can generally be kept shorter. The second, and chief
reason, is the solid, continuous ground plane. The advantage of the
ground plane isn't capacitance reduction as you say, but much lower
ground inductance. In a typical PC board layout, currents from various
parts of a circuit have to flow through ground traces which can have
considerable impedance at RF. This causes voltage drops which are
related to each of the currents. The voltages are applied to the
connected circuits, resulting in crosstalk and feedback.

It's usually possible to get by with a fairly abbreviated ground system,
but it can take an awful lot of care and knowledge to do it -- I haven't
even run across a lot of otherwise skilled engineers who are good at it.
The average home constructor is much more likely to succeed on the solid
plane provided by "ugly" construction. It's not uncommon for an "ugly"
prototype to work well and a PC board version fail -- unless you have
the luxury of using a multiple-layer PC board where you can devote one
layer to being a solid ground plane. The chances of succeeding with a PC
depends heavily, of course, on the nature of the circuit -- some are
vastly more tolerant than others.

I personally like "ugly" construction also because it's much faster than
making a PC board and, if done right, can be as rugged. Of course the
advantages of a PC board are obvious when making multiple copies of a
project.

I know of what I speak -- I've spent a career designing electronic test
equipment, and do consulting in the EMC field (electromagnetic
compatibility, dealing with such issues as crosstalk and RFI). And I've
done a considerable amount of RF homebrewing.

Roy Lewallen, W7EL

Basil B. wrote:
Hello all

I've been doing a fair bit of internet reading about RF construction
projects. I'm still confused about something.

Most authors, including those in the ARRL Handbook, seem to espouse
"ugly construction" and a variant called Manhatten construction. I
understand that the reason is that these techniques minimize
capacitance by providing a large ground plane. Ugly construction seems
to also encompass perfboard construction with wire traces or direct
component-to-component connections. This seems to me to be not much
better than using pre-printed boards whose traces match, in geometry,
those of solderless prototyping boards.

I do understand that the solderless boards are inadequate for RF work,
but are the pre-printed perforated "protoboards" also inadequate.

Call it an OC tendency, but ugly construction is, well, ugly. Of
course, I want to use the best techniques for what I'm doing, and if UC
is the way to go, then that's what I'll do.

I'd appreciate your opinions on this.

Thanks
Basil B.

"Basil B." wrote in message
oups.com...

Call it an OC tendency, but ugly construction is, well, ugly. Of

Take a peek at the work of K8IQY who really made Manhattan construction
popular, or K7QO, who has some tutorials on the subject. Their work is
anything but ugly.

Mine on the other hand ...

...

I'd like to thank you all for your input. Obviously, a process that
works and has high quality of results is much better than one that
merely looks good. I did research the sites of the people you mention.
I just wanted to be sure I understood the issues, and you've all
helped. Thank you.

Regards
Basil B.

On 30 Dec 2005 09:32:25 -0800, "Basil B." wrote:

Hello all

I've been doing a fair bit of internet reading about RF construction
projects. I'm still confused about something.

Most authors, including those in the ARRL Handbook, seem to espouse
"ugly construction" and a variant called Manhatten construction. I
understand that the reason is that these techniques minimize
capacitance by providing a large ground plane. Ugly construction seems
to also encompass perfboard construction with wire traces or direct
component-to-component connections. This seems to me to be not much
better than using pre-printed boards whose traces match, in geometry,
those of solderless prototyping boards.

I do understand that the solderless boards are inadequate for RF work,
but are the pre-printed perforated "protoboards" also inadequate.

Call it an OC tendency, but ugly construction is, well, ugly. Of
course, I want to use the best techniques for what I'm doing, and if UC
is the way to go, then that's what I'll do.

I'd appreciate your opinions on this.

Thanks
Basil B.

I've done carfully constructed dead bug (ugly) RF hardware that works
well at 2.4ghz and is not ugly It's a very effective techniques and
with modest care it's difficult to do better with etched circuits at
VHF or higher.

Some of my best radios and test gear have been built this way
and some test items are now several decades old. It can be very
rugged as well.

Allison
KB!gmx

I've done carefully constructed dead bug (ugly) RF hardware that works
well at 2.4ghz and is not ugly It's a very effective techniques and
with modest care it's difficult to do better with etched circuits at
VHF or higher.

Some of my best radios and test gear have been built this way
and some test items are now several decades old. It can be very
rugged as well.
============================
Ugly construction can in fact be very neat.
I normally use double sided PCB and drill holes to suit such that
components to be grounded can be fitted perpendicular directly to the
board without wire ends. These then also serve as support for
non-grounded components. If non-grounded components are on their own I
fit 10 MOhm resistors as 'practical stand-off insulators'. Where
inductance is a critical element I use metal film resistors for this
duty ,but normally carbon film resistors are fine.
All board mounted components are soldered to board on both sides such
that both copper sides are bonded at various places.
Integrated circuit are glued 'dead bug style' with ample opportunity to
connect other components.
For VHF and higher I line the board edges with folded very thin copper
strip.
I am fortunate having found a roll with 6mm wide strip with a total
length sufficient 'for life', at a flea market.


Frank KN6WH / GM0CSZ

In article .com,
says...
I'd like to thank you all for your input. Obviously, a process that
works and has high quality of results is much better than one that
merely looks good. I did research the sites of the people you mention.
I just wanted to be sure I understood the issues, and you've all
helped. Thank you.

Regards
Basil B.



Ugly is definitely in the eye of the beholder. If it bugs you, then
you might consider enclosing your modules in neat-looking Hammond boxes,
connecting them with exotic gold-plated SMA/SMB/SMC hardware. When the
lid is screwed down on the box, nobody can see the ugly stuff. I've
built (almost) an entire receiver this way:

http://www.speakeasy.net/~jmiles1/ke...x/equinox.html

Only the 1st LO synthesizer(s) are built on PC boards, and it wasn't
strictly necessary even in those cases. The prototype LO was built
ugly-style, and works just fine.

Perfboard can best be thought of as equivalent to conventional single-
sided PC boards, with no ground plane. As Roy pointed out, you often
don't care about stray capacitance as much as you care about having
ubiquitous access to a low-inductance ground. You don't get that with
either single-sided PC boards or perfboard.

Personally, I don't think much of the idea of fabbing a PC board for a
one-off project, unless it involves newfangled chips with more pins than
you can see. And perfboard, for me, is not the method of choice for
anything but digital work -- although people have certainly used it to
build some very nice gear.

-- jm

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