Part 1: What is a Rockmite, Acquisition and PCB Assembly

DL4AND’s Rockmite
Part 1: Acquisition and Assembly of the Printed Circuit Board (PCB)
Part 2 describes installation into casing and experiences during operation.
Part 3 shows the setup during the first operation “in the Field”.
What is the Rockmite?
To experience the fun of homebrewing, I ordered a Rockmite from “Small Wonder
Labs” of OM Dave, K1SWL, in USA.
It is a minimalistic QRP CW Transceiver which works only on one frequency. There
are versions for different bands, I chose the 40 m version (7030 kHz is the
recommended QRP frequency there).
Output power is 0.5 Watts (!), no calibration necessary. It even features a keyer (that
produces the dots and dashes semi-automatically). So if the transceiver was no
good, I would have had at least a morse practicing device with dot/dash
mechanism… ☺
If you wish to know further details, such as how the radio is operated, please enter
“Rockmite” into “Google” or visit Dave’s website, www.smallwonderlabs.com.
Ordering in the United States
I ordered five kits from Dave as I could convince several club colleagues to get one
as well.
Payment worked very simple using my PayPal-Account which I already had
established for my Ebay activities.
Dave responded timely and promised shipping within the next three weeks.
Unfortunately, it took six weeks while my money was already transferred upon
ordering…
I was able to track my order status on Dave’s web site.
No customs fees are due for importing amateur radio gear into Germany, only 19 %
VAT have to be paid. This was very simply achieved by paying the VAT cash to the
parcel messenger of DHL German Parcel Service. I was glad I didn’t have to go to
the customs office!
I finally had the goods in front of me. Inside the box, there were several pages of
documentation of the German Customs Office in Frankfurt, five kits in plastic bags
and five brief building instructions (with a web address to download a comprehensive
building manual – highly recommended!)
The Assembly
I had considered two different casings: One casing model TEKO 4/B which could
have housed a battery box as well, and a ball pen present tin box.
TEKO 4/B,
Rockmite PCB
and battery box
for AA cells.
I decided to ruin the tin box first ☺
Overview, from top to bottom:
•
“Third hand” assembly aid (very useful!)
•
TEKO casing
•
Battery box for 10 ea. AA batteries 1.5 V
(provides 12 V when using 1.2 V rechargeable cells)
•
Clockmaker’s magnifying glass to check the solder joints
•
Solder wick (necessary)
•
Rockmite components
•
Tin box with lid and Rockmite PCB inside
•
Resistor color code table (not necessary as color codes are listed in the
manual)
•
Rockmite components
•
Parts purchased separately: Push button, jacks, plugs, potentiometer
My work bench – laptop on L.H. side so I could e-mail Dave immediately in case of
questions ;-)
The largest challenge right at the beginning is the installation of the SMD chip. This
part is only 5 mm wide but has 8 pins!
Someone like me, who has last soldered a PCB kit five years ago and does not have
an appropriate small soldering iron, must seek assistance for this!
My thanks are going to Andreas,
DD6YG. He is a professional
and had his gas soldering iron
with him during a club meeting!
ll
All further assembly was done by me.
At first, I sorted the components.
The English manual is very useful. It explains in detail what the reading on the parts
means (e. g. 223 means 0.022 micro Farad – I would have never figured this out
myself…)
Parts list, installation diagram and PCB printing are facilitating assembly
considerably, I never had to look at the circuit diagram ;-)
I found it helpful to cross
out every installed part on
the parts list immediately.
This way I could keep track
of what parts are still to be
installed.
Dave has a system of very
clear instructions and PCB
labelling for correct polarity
of parts such as diodes.
This helps to prevent
installing parts in wrong
polarity.
My assembly strategy: Condensers first, whereas I was not going strictly by C1, C2
C3 etc. But I distributed condensers across the PCB, fitting them into their designated
spot.
Upon soldering, I first
soldered only one pin
until I had all first pins
soldered around in a
circle, then I started to
solder the second pins.
This way I minimized
the heat stress on the
PCB and parts, because
my 40 W soldering iron
was too strong for this
job. Dave recommends
a 25 W iron.
I bent the pins slightly apart to prevent the parts from falling out upon turning the PCB
around for soldering.
However, a removal of parts soldered in the wrong spot is harder, so do not bend
pins too far apart!
Of course, at the end of the assembly, I had a resistor extra which did not seem to
belong anywhere – until I realized I had installed another resistor in its place ;-)
I was lucky enough to unsolder this resistor without loosening the traces of the
PCB…
The labelling of the diodes could only be read with the magnifying glass, I therefore
simply wrote it again onto their bags to facilitate further assembly. The magnifying
glass was also very helpful to identify the color rings on the resistors and inductances
(below) – at least for someone in my age….
Assembly progress
Only quartzes and semi-conductors are to be installed
PCB assembly completed – except for two condensers – they were not supplied!
Too bad!
I e-mailed Dave the same evening. I’ve got his reply the next day. He apologized and
promised to deliver the missing condensers immediately. Five days later I received
them in a letter. The postage was more expensive than the value of the
condensers ;-)
Finally, I’d like to commend Dave for his very good assembly manual. It was obvious
that much experience from practice (i. e. people who had a problem with assembly
and Dave had helped them) has flown into this manual.
When “Google”ing I also found this manual in German.
It took me approx. 6.5 hours for the assembly, whereas I intentionally took my time
because I was lacking soldering practice…
It took me another approx. 4 hours for the preparation of the casing, installation of the
PCB and the jacks and the wiring. These subjects are described in part 2, installation
into casing and experiences during operation.
vy 72 (no typo, but the greeting of the QRP enthusiasts ;-),
Andy, DL4AND
Contact me: DL4AND ‘at~ darc –dot* de