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!

Hi Dave,

"Dave Platt" wrote in message
...
One of the recipes for making stable, friendly, and reproducible
designs at RF seems to be to minimize the impact of parasitic
reactances.

Certainly true, although my feeling is that 'ugly' construction above a ground
plane creates _well controlled_ parasitics that tend not to change much based
on, e.g., waving your hand above the PCB, mounting the PCB close to a metal
chassis, etc.

Joel Kolstad wrote:
Hi Dave,

"Dave Platt" wrote in message
...

One of the recipes for making stable, friendly, and reproducible
designs at RF seems to be to minimize the impact of parasitic
reactances.


Certainly true, although my feeling is that 'ugly' construction above a ground
plane creates _well controlled_ parasitics that tend not to change much based
on, e.g., waving your hand above the PCB, mounting the PCB close to a metal
chassis, etc.

My experience is that the most common and troublesome parasitic
reactance in modern solid-state circuitry is, by far, the inductance of
the ground system. And that's just where "ugly" construction shines --
it makes that inductance as small as possible.

Roy Lewallen, W7EL

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.

I tend to use PCBs, but I make them single-sided on double-sided PCB
stock, so that there is a continous ground plane on the top.

Leon

"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.