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Author Topic: Looking for a SMALL tranceiver...  (Read 2883 times)
KE7FD
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« on: October 31, 2010, 02:25:50 PM »

My wife discarded a Godiva Dark Chocolate Pearls box which I recovered as I am certain it would make an excellent QRP unit if I could come up with a transceiver circuit that will fit inside the box. Can anyone help me out with a recommendation?  The inside dimensions of the box are (HxWxD) 3"x1.5"x.75".  If the circuit is small enough I would be able to house the needed plugs in it coiled up ready for use.  A keyer would not be required.


Glen - KE7FD
« Last Edit: October 31, 2010, 03:05:23 PM by Glen Roberts » Logged
KA7PLE
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« Reply #1 on: October 31, 2010, 05:07:28 PM »

The smallest rig I can think of would be the Rockmite series from Small Wonders.  Or an SST from Wilderness radio, but those come with clam shell type very nice metal case.


73
KA7PLE
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KE7FD
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« Reply #2 on: October 31, 2010, 06:08:03 PM »

Thx.  I have a RockMite40 that works very well.  I came across this slammer box and I want to believe there's a way to make it radiate.  I may have to do the thing that we all aspire to, design my own (based on what I can find in a newer handbook).
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WB6BYU
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« Reply #3 on: October 31, 2010, 07:33:22 PM »

That's a bit longer than the Altoids "Tiny Tin" case.  A friend of mine has been planning a transceiver
that would fit in one of those.  Using a tube.

Certainly the case is large enough for a surface mount version of the Pixie.
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KE7FD
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« Reply #4 on: November 05, 2010, 07:28:27 AM »

I decided to walk down a different path, the tiny box will have to wait.  I ordered a Small Wonder Labs SW+40 and to augment the tuning, a generic frequency counter from some other source.  I'm replacing the standard tuning pot with a 10-turn pot and a vernier dial to really fine tune the unit. There's a lot of chatter among the Yahoo RockMite group about getting stepped on at 7030 and 7040, so using a vfo just seemed to make sense; I may have to take precautions to thermally stabilize the unit to limit drift.  When it's complete, it'll be something of a hybrid but will fit my taste of operating.  Thanks again for the comments.

Glen - KE7FD
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WB6BYU
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« Reply #5 on: November 05, 2010, 08:30:19 AM »

We ordered some of the 40-40 boards (early version of what became the SW40+) from FAR Circuits and
built them up with parts from the junkbox.   Makes a nice small transceiver.  I used a 10-turn "Knob-Pot"
for tuning as it takes up virtually no room inside the case, but they are rather expensive new, and the
glass cover over the dial (the analog version with two hands like a clock face) cracks easily.  But they
are wonderful for tuning 50kHz very smoothly in such a circuit, and lighter than a conventional 10-turn
pot and counter dial.

The rig uses an op amp for the audio output, which doesn't have a lot of drive.  I had to try a number of
sets of Walkman headphones (connected in series for higher impedance) to find one that gave enough
volume.  But there are some small speakers around in the 100 ohm range that should work better, and
I picked up some military headphone inserts that are very sensitive that I plan to use.  If you've got
a set of headphones that are 600 ohms or higher they should work fine.

The rig really is pocket sized.  Next step may be to add some internal lithium batteries to make it
self-contained.

I haven't had a problem with temperature stability once I changed out the poly film capacitors with
polystyrene and NP0/C0G ceramics.
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KE7FD
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« Reply #6 on: November 05, 2010, 05:59:50 PM »

BYU, I'll keep those improvements in mind as I built it.  I picked up both a 10-turn pot and a vernier dial for around $17 total after shipping from Circuit Specialists out of Mesa, Arizona.  I don't think I'll need to use both at the same time but one or the other will do the job.

Glen - KE7FD
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