1 Dec 2012
The first Tenbox Schematic
The breadboarding of the Tenbox 10m AM transceiver for local cross-town night-time nattering is almost complete now, with just a receiver audio amplifier to drive a loudspeaker to be added. Power output is a conservative 250mW AM carrier (peak power around 1W). The first schematic draft is shown here, but as always I warn that I may have forgotten to correctly label some parts and the values may change as the circuit is further developed. I hope to road test this over the weekend going out in the car with a mag-mount antenna whilst AM beaconing with the rig from home. As with WISPY, I have paralleled up 4 2N3904 transistors for the PA. This is a very inexpensive way of making a 10m PA stage! The alternative, such as a 2N3866 would be about 5-10 times more expensive.
29 Nov 2012
Small Wonder Lab Kits
This was the notice on his website last week:
"Folks-
I took a ‘leap
of faith’ in 1996, leaving the corporate world to undertake ‘Small Wonder Labs’
as a full-time venture. Since then, it’s
been a great experience. I have to face facts, though: I’m getting older. The shortcomings in
vision can be overcome with close-up glasses. More troublesome, though, are the
muscular issues from spending hours a day at the computer, or with my head
down, sorting parts into bowls.
Over the years, I’ve assisted countless customers with no-questions-asked replacement parts and troubleshooting advice. The issue of repairs has been problematic, though. While no one really objects to paying $50/hour to have a $1000 rig repaired, that’s not true of a $50-100 kit. I’ve had some good people doing repair work for me, but it’s just not economically viable. Neither can I do the work in a timely manner. Therefore, and effectively immediately, I will not be accepting returns for troubleshooting/repair.
It’s not clear to me at this point if I’ll release any additional product offerings. Although I love the creative process involved in a new design, everything that follows is now just ‘work’. Along the way, I lost the ‘hobby’ aspect of ham radio. I have not been on the air in almost 5 years. I want my hobby back!
I’ve finished our home here in the woods of New Hampshire, and it’s time for me to move on to other interests. I’ve still got a garage/barn to build, a garden that grows larger each year, and a wealth of outdoor activities I can’t seem to find the time for. Retirement is clearly not for the faint-of-heart!
I’ll continue to sell RockMites forever, apparently. Demand is still brisk, with more than 8000 of them out there so far. Ongoing activity for the RockMite as well as support for ‘legacy’ kits occupies me for 2-3 hours each day. At this stage of my life, that’s ‘enough’.
73- Dave Benson, K1SWL
19 November
2012"
Over the years, I’ve assisted countless customers with no-questions-asked replacement parts and troubleshooting advice. The issue of repairs has been problematic, though. While no one really objects to paying $50/hour to have a $1000 rig repaired, that’s not true of a $50-100 kit. I’ve had some good people doing repair work for me, but it’s just not economically viable. Neither can I do the work in a timely manner. Therefore, and effectively immediately, I will not be accepting returns for troubleshooting/repair.
It’s not clear to me at this point if I’ll release any additional product offerings. Although I love the creative process involved in a new design, everything that follows is now just ‘work’. Along the way, I lost the ‘hobby’ aspect of ham radio. I have not been on the air in almost 5 years. I want my hobby back!
I’ve finished our home here in the woods of New Hampshire, and it’s time for me to move on to other interests. I’ve still got a garage/barn to build, a garden that grows larger each year, and a wealth of outdoor activities I can’t seem to find the time for. Retirement is clearly not for the faint-of-heart!
I’ll continue to sell RockMites forever, apparently. Demand is still brisk, with more than 8000 of them out there so far. Ongoing activity for the RockMite as well as support for ‘legacy’ kits occupies me for 2-3 hours each day. At this stage of my life, that’s ‘enough’.
73- Dave Benson, K1SWL
ARRL 10m contest (48hrs Dec 8-9th)
A reminder that the ARRL 10m contest is on next weekend (not this) over the full 48 hours Dec 8th and 9th. As conditions on 10m are pretty good right now this will be a good chance to work a fair number of US, Canadian and Mexican states and provinces, even with QRP levels in CW or SSB. I'm away on the Saturday but hope to be on for the Sunday.
26 Nov 2012
Cutting big pieces of copper laminate
When I was working I had access to a guillotine to snap out large pieces of copper laminate to convenient sizes for project breadboards. Being retired I no longer have this method to hand. SO, I asked a question on the GQRP Yahoo group this evening to find out what other people did. Several suggestions but the favourite is "scoring and snapping", summarised by the post from Duncan G4DFV which I have reproduced below.
"My method of cutting large pieces of copper laminate:-
- Place a steel rule along a previously drawn line on the board where you require to cut.
- Pressing down firmly on the rule, using a stanley or other utility knife, score along the line.
- Repeat the scoring in the same cut for perhaps 10 times, then
- looking at the edges of the board, you will see each point where the
- scoring starts and finishes.
- Carefully mark these points over on to the other side of the board and
- place the rule exactly along a line between these points and score as before.
- After about 10 scorings, place the board on a flat surface such that the
- scored line is on a straight edge.
- Holding the board down with one hand, press down over the straight edge with the other.
- The board should break cleanly along the scored line.
- Any uneven/rough edge can be smoothed with sandpaper.
Duncan G4DFV"
Tenbox TX progress
Good progress today with the transmit side of my Tenbox 10m AM transceiver.
The series modulator was breadboarded a few days ago, so today I built the 3rd overtone oscillator, the buffer and the modulated PA stage. Results were as expected with around 50-60mW of clean well modulated AM available at the output. With a single linear amplifier with around 10-13dB gain (easy at 29MHz) this will take me into the 500mW-1W carrier level, which is my design aim. As I did not have a suitable 29.05MHz crystal (anyone know where these can be obtained cheaply?) I used a 28.500MHz one on a dummy load. With this frequency, any range tests will have to be done at night to avoid QRM to SSB stations.
When the linear is added , maybe even before then, I'll do a local "drive around" test with the TX on "speech beaconing" mode (using an MP3 file on the PC) and with the RX attached to a mag-mount antenna on the car. This will establish the useable local coverage. Assuming this power level is OK, I'll then complete the full design on a tidy breadboard and publish the initial schematics on my blog and website. After that, a PCB may be in order and a neat enclosure.
This project is great fun: a simple, straightforward and easily reproducible design and a project that will be useful at the end. Much more fun than working DX with 400W and a 5 el beam in a contest with a £5k commercial HF transceiver. Honestly, I'm having a real ball with this.
The series modulator was breadboarded a few days ago, so today I built the 3rd overtone oscillator, the buffer and the modulated PA stage. Results were as expected with around 50-60mW of clean well modulated AM available at the output. With a single linear amplifier with around 10-13dB gain (easy at 29MHz) this will take me into the 500mW-1W carrier level, which is my design aim. As I did not have a suitable 29.05MHz crystal (anyone know where these can be obtained cheaply?) I used a 28.500MHz one on a dummy load. With this frequency, any range tests will have to be done at night to avoid QRM to SSB stations.
When the linear is added , maybe even before then, I'll do a local "drive around" test with the TX on "speech beaconing" mode (using an MP3 file on the PC) and with the RX attached to a mag-mount antenna on the car. This will establish the useable local coverage. Assuming this power level is OK, I'll then complete the full design on a tidy breadboard and publish the initial schematics on my blog and website. After that, a PCB may be in order and a neat enclosure.
This project is great fun: a simple, straightforward and easily reproducible design and a project that will be useful at the end. Much more fun than working DX with 400W and a 5 el beam in a contest with a £5k commercial HF transceiver. Honestly, I'm having a real ball with this.
25 Nov 2012
10/20W versions of popular transceivers
In the Japanese home market, several of the transceivers available in the USA and Europe are available in lower power versions too. For example, the IC7000 is available as a 50W version and a 20W version. Prices aren't always lower though. For example on the www.icom.jp site, the IC7000S (20W) is available at 168000 yen, the same price as the 100W radio.
The reason these lower power radios are not available outside of Japan is clear: lack of sales volumes and lack of the necessary approvals. It is a pity that the major dealers like W&S and Martin Lynch don't offer to import these on request though if they met EMC specs as I can imagine a reasonable market with QRPers with a bit of advertising: they have enough space in RadCom and PW after all!
The reason these lower power radios are not available outside of Japan is clear: lack of sales volumes and lack of the necessary approvals. It is a pity that the major dealers like W&S and Martin Lynch don't offer to import these on request though if they met EMC specs as I can imagine a reasonable market with QRPers with a bit of advertising: they have enough space in RadCom and PW after all!
How to avoid expensive calls to 0870 numbers
The website http://www.saynoto0870.com/ is a useful resource in the UK if you are looking for a lower cost, or even free, way to contact companies such as Virgin Media or Dell where an expensive 0870 call make be needed. I get infuriated when big companies keep me waiting on an expensive call saying things like, "your call is important to us" then waste the next several minutes with drivel.
Most of these alternative numbers get in "via the back door" and work on the assumption that you will be transferred internally to the correct department. It may not always work, but if you want to save a few pounds it is worth a go.
Most of these alternative numbers get in "via the back door" and work on the assumption that you will be transferred internally to the correct department. It may not always work, but if you want to save a few pounds it is worth a go.
CQWW CW - guess who forgot!
Julian G4ILO has posted a piece on his excellent blog about the CQWW DX CW contest this weekend. Well, yesterday was my wife's birthday and we had family here and today I did my tax return. In the process I managed to miss this contest completely! For some reason I thought it was NEXT weekend. Never mind, there will be other occasions to work the DX.
The hazards of LF operating
On the LF reflector there was a salutary message from Mike G3XDV today. Doing some 136kHz tests overnight his loading coil caught fire melting his flat roof extension!
LF amateur radio can be very dangerous as extremely high voltages and/or high currents can be generated with even quite modest powers because of the electrically short antennas. This is one reason why I stick to QRP(ish) powers on 136 and 500kHz.
See Mike's post:
LF amateur radio can be very dangerous as extremely high voltages and/or high currents can be generated with even quite modest powers because of the electrically short antennas. This is one reason why I stick to QRP(ish) powers on 136 and 500kHz.
See Mike's post:
This picture (linked from Mike's blog) shows the damage.It begs the question of how readily will an insurance company pay up when an amateur installation fails?"I am currently off the air following my loading coil catching fire and damaging the house. I have had to take my mast down to allow access to the builders who are repairing the damage. Fortunately I was insured.
Damage to the G3XDV loading coil ....and roof! See http://g3xdv.blogspot.com
Hopefully I will be able to receive before Christmas and transmit again some time in January.
Details and pictures are on my blog at:http://g3xdv.blogspot.com
Mike, G3XDV"
More 10m (28MHz) Projects
With the Tenbox coming along just fine - I should have a completed breadboard version on-air this week - I am beginning to think that I could spend nearly all my free time designing different ideas for this, my favourite, band!
Here is just a brief list of some of my 10m ideas (all do-able with some time):
What occurs to me, if I had the time, is that a mini-series in a magazine like PW or RadCom entitled "Ten Projects for Ten Metres" would be a nice idea. 10m is one of the best bands for homebrewing as layout is not too critical, as long as sensible RF rules are followed, antennas are small, superb DX is possible in the better years and Es DX possible for 4-5 months every year, local ranges are useful for nattering across town. All in all, this band has SO much to offer.
Here is just a brief list of some of my 10m ideas (all do-able with some time):
- 10m QRP AM transceiver (Tenbox)
- 10m QRP DSB transceiver
- 10m pocket SSB/CW "holiday" receiver
- 10m mixer-VFO controlled CW transceiver
- 10m compact portable antennas for mobile and hand-portable
- 10m VXO controlled QRP TX
- 10m phasing SSB transceiver (10W)
- 10m beacon RX
- 10m test box (power meter, ATU, SWR bridge, FS/mod meter)
- Modules for 10m rigs (VXO, mixer-VFO, LPF, TX strip, DC RX, AM modulator, audio power amp etc)
What occurs to me, if I had the time, is that a mini-series in a magazine like PW or RadCom entitled "Ten Projects for Ten Metres" would be a nice idea. 10m is one of the best bands for homebrewing as layout is not too critical, as long as sensible RF rules are followed, antennas are small, superb DX is possible in the better years and Es DX possible for 4-5 months every year, local ranges are useful for nattering across town. All in all, this band has SO much to offer.
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