The
Rockmite is a super little transceiver kit put out by Small Wonders
Labs. Mine cost $29. It is very small. You can make contacts on it but
its somewhat challenging. I put out many CQ's and called many others to
no avail over a few days time.
To me the biggest shortfall to making more frequent contacts was the power output, selectivity of the receiver, and frequency rockbound.
My Yaesu FT-817 puts out 5 watts and i can make contacts with it fairly easy on cw. So the first thing to soup up the Rockmite was to build an amp. The Miniboots kit is no longer in production as a kit (at least at the time of this writing) so i proceeded to make my own. The schematic is readily available on the Web. It utilizes an efficient MOSFET.
Here is a summary of some tips i sent to a station in England that inquired how i built my amp;
- Built on perf board, no special type construction
- Used the IFR510 MOSFET as the IRF510 seems to be scarce
- Tried to keep the Toroids spaced a bit (maybe 1/2 inch or so)
- The MOSFET will need a small heatsink
- Mounted some of the low profile components on the bottom of the board to make the unit more compact
- Used Poly capacitors and a 680pf ceramic disk capacitor in place of the SM capacitors specified mainly because that is what i had on hand. They seemed to work fine.
- Used a small 12v relay. The size that fits a DIP socket.
- Did the Rockmite mod using the heavier final transistor (you can find on the Web) so more effectively drive the amp.
- Used a 10ohm resistor in place of the 100ohm Potentiometer. This allows for about 7 watts output at 14 volts and 5 watts at 12 volts.
- You can move the coil turns on the toroids to peak the amp but this does not seem to be critical. The design is fairly bulletproof IMHO.
A picture of where i am at now with the Rockmite and Miniboots mounted on a board. As i get time, i plan to detail this webpage and maybe add some O Scope waveforms, etc. Also detail how the audio filter, cabinet mounting, vxo, crystal switching, etc workout.
Oct 08. Now for the audio filter. I constructed a 4 section audio filter from 5Z4FT's website (http://www.qsl.net/5z4ft/bpf.gif). Thanks Andrew!
From that e-place, i ordered 8000 surface mount device capacitors and resistors. Quite a bargain for 8000
components. After building with through hole on and off for decades, this was my first usage of significant numbers of smd components. I used the perf board with the little copper circles around the holes. I have not seen anyone on the net using this for smd so i was skeptical it would even work. Using my common sp-25 weller 25watt soldering iron. i assembled this.
It was helpful to use a highlighter as i went along to highlight on my schematic what i had installed. I used no placement technique other than common sense. One thing that is easy to do is to have solder bridges underneath the smd components, so check for shorts with a meter as you go along. There are some good smd soldering tutorials on the net. Obviously my neatness with the perf boards and smd's is not picture perfect.
For the IC's & electroylic capacitors i used through hole components. No particular reason other than this is what i had on hand.
To my delight, this thing worked first time i hooked it up. And it works very well. Using all 4 sections it is really narrow. Just had a qso with N9RLO. He must have zero beated and i was able to kick in all four sections and still hear him. It nulled everyone else out!
A few pictures below. The top of the audio filter board, the bottom with the smd components, and the entire setup with the qso. Amp, rockmite, and audio filter. Coming up, vxo, rit, probably a switch to go to the skcc frequency 7055. Then probably mounting it all neatly in an enclosure.
To me the biggest shortfall to making more frequent contacts was the power output, selectivity of the receiver, and frequency rockbound.
My Yaesu FT-817 puts out 5 watts and i can make contacts with it fairly easy on cw. So the first thing to soup up the Rockmite was to build an amp. The Miniboots kit is no longer in production as a kit (at least at the time of this writing) so i proceeded to make my own. The schematic is readily available on the Web. It utilizes an efficient MOSFET.
Here is a summary of some tips i sent to a station in England that inquired how i built my amp;
- Built on perf board, no special type construction
- Used the IFR510 MOSFET as the IRF510 seems to be scarce
- Tried to keep the Toroids spaced a bit (maybe 1/2 inch or so)
- The MOSFET will need a small heatsink
- Mounted some of the low profile components on the bottom of the board to make the unit more compact
- Used Poly capacitors and a 680pf ceramic disk capacitor in place of the SM capacitors specified mainly because that is what i had on hand. They seemed to work fine.
- Used a small 12v relay. The size that fits a DIP socket.
- Did the Rockmite mod using the heavier final transistor (you can find on the Web) so more effectively drive the amp.
- Used a 10ohm resistor in place of the 100ohm Potentiometer. This allows for about 7 watts output at 14 volts and 5 watts at 12 volts.
- You can move the coil turns on the toroids to peak the amp but this does not seem to be critical. The design is fairly bulletproof IMHO.
A picture of where i am at now with the Rockmite and Miniboots mounted on a board. As i get time, i plan to detail this webpage and maybe add some O Scope waveforms, etc. Also detail how the audio filter, cabinet mounting, vxo, crystal switching, etc workout.
Oct 08. Now for the audio filter. I constructed a 4 section audio filter from 5Z4FT's website (http://www.qsl.net/5z4ft/bpf.gif). Thanks Andrew!
From that e-place, i ordered 8000 surface mount device capacitors and resistors. Quite a bargain for 8000
components. After building with through hole on and off for decades, this was my first usage of significant numbers of smd components. I used the perf board with the little copper circles around the holes. I have not seen anyone on the net using this for smd so i was skeptical it would even work. Using my common sp-25 weller 25watt soldering iron. i assembled this.
It was helpful to use a highlighter as i went along to highlight on my schematic what i had installed. I used no placement technique other than common sense. One thing that is easy to do is to have solder bridges underneath the smd components, so check for shorts with a meter as you go along. There are some good smd soldering tutorials on the net. Obviously my neatness with the perf boards and smd's is not picture perfect.
For the IC's & electroylic capacitors i used through hole components. No particular reason other than this is what i had on hand.
To my delight, this thing worked first time i hooked it up. And it works very well. Using all 4 sections it is really narrow. Just had a qso with N9RLO. He must have zero beated and i was able to kick in all four sections and still hear him. It nulled everyone else out!
A few pictures below. The top of the audio filter board, the bottom with the smd components, and the entire setup with the qso. Amp, rockmite, and audio filter. Coming up, vxo, rit, probably a switch to go to the skcc frequency 7055. Then probably mounting it all neatly in an enclosure.