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NN4CW's Super Lightweight AT Sprint III (Skinny
Minnie)
Over the past few months, Gil Stacy NN4CW
and I have exchanged several emails regarding the ATS3. His
experience in building two Sprints, and various experimentation
along the way, has resulted in a rig that is lighter than most
others - lighter packaging, lighter keying and a lighter power
source.
I asked Gil if he'd mind if I posted his info
and photos here. He said, "No way" - so if you see
Gil looking for me, please distract him with a LiPoly battery
while I run for cover ;-)
de NN4CW:
Here's the new ATS3 (Skinny Minnie) that I
just finished that I intend to use in December's Spartan Sprint.
With 80 meter and 40 meter boards, battery, straight key and
single earbud, the weight is 0.149 pounds or 2.38 ounces.
For enclosure, I used a skeletonized aluminum
sardine can (Reese). The white panel and bottom are fiberglass
reinforced paper with a plastic coated surface-cut from a heavy
duty envelope. After trimming the can to Altoids tin height
and removing a center panel with my dremel cutoff wheel, the
can's weight went from .4 oz to .2 oz. While not as sturdy as
an Altoids tin, it is fairly stout to be made from only .012"
aluminum. With washboard sides and indented bottom, it's not
flimsy.
The earbud and wiring are from a cheap hands
free cellphone adapter from Wally World. The battery is a LiPo
7.4 V (8.4 V fully charged) with a weight of .67 oz. The straight
key is made from parts of a telephone relay switch. It has silvered
contacts. The "knob" is a disk cut from a wine cork.
I soldered to the top reed the cutoff head with .2" of
the shaft of a bronze boat nail that is ribbed. The ribbed edges
hold the cork without adhesive. Key and earbud are wired directly
to the board. Power connector is female JST connector and antenna
is male JST connector which prevents screwing the pooch by feeding
power into the antenna connector.
On the paddle/key jack pads, I soldered wire
loops to which is soldered a two pin SIP connector to short
ground to first pad which shorts the dot pin of the MCU so that
the straight key can be used. Another loop is soldered to the
dash pad. By removing the SIP connector, I can clip my paddle
in to program a CQ string into memory for use in the Sprint.
I connected the board to the can with epoxy.
Epoxy does not touch board - masking tape is on both sides.
I cut another cork disk which I quartered, then stuck a short
piece of toothpick into each quarter. I applied Crazy Glue to
each section of toothpick. On the top of the board, I placed
a fillet of cut up fiberglass insulation and "5 Minute"
epoxy at each hole to hold the board tightly against the cork
pieces. When that dried, I used more fillet to glue the corks
to the bottom of the can. I roughed up the can with sandpaper
and covered the bottom with masking tape as well.
On Friday, with a fully charged battery, I
worked 20 meters for 3 hours, including EI/YL1ZF (Ireland).
It was more activity that I would have S and P'ing during a
2 hour Sprint. The voltage dropped to 7.82 and watts fell from
2 to 1.7.Photos show full station and attachment of board to
can. I ran the straight key and earbud wires through jack mounting
holes and knotted the ends for strain relief. Key is a little
mushier than what I like to use, but I've gotten used to it.
Power Source
The charger is a Thunderpro. The Thunderpro
charger is for Lithium Polys and must be hooked to a power source
to operate. You choose cell count and mah and it does the rest.
It's 50 bucks and the 11.1 V 300 mah is $25. The JST connectors
are very light weight and cost under 2 bucks from the same source.
The battery I used Monday was a 3-cell, 11.1V, 300 mah. It weighs
.98 ounces and raised my station weight to .171 lbs but with
a power gain of 8 dB. At the beginning, I was at 12.6 V with
5 watts out. After 2 hours, 11.6 V and 4.5 Watts, which is pretty
amazing. The batteries and charger come from AeroMicro.
Li-Poly batteries are vilified by some because
of the earlier cellphone fires, but they are what are in cellphones
now and most folks I know carry them in their pants pockets.
;) The fires resulting from use of R/C planes can be partially
attributed to the rougher use in the planes which damages the
batteries which occasionally erupt in flames during the charging
cycle.
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ThunderPower Li-Po Charger |
300 mAh, 11.1V Li-Po Battery |
W1MT's ATS3 Notes & Cal Procedure |
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