Dave Richards AA7EE

June 24, 2013

The Etherkit CRX1 – A Handy Little VXO-controlled 40M Receiver Kit

Filed under: Ham Radio,QRP — AA7EE @ 5:14 pm
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Just a quick post to mention that Jason NT7S has developed what looks like a neat little 40M receiver kit, the CRX1.  It is VXO controlled, covers about 7030 – 7034KHz, and comes with  muting, transmit/receive switching and user-enabled sidetone, as well as a port for connecting an external VFO.  It sounds like a great little receiver for combining with home-brew transmitters and with the external VFO port, there is room for further development. It is all SMT, but with larger-sized SMT components and a board that is not very densely packed, making it a great first project for an experienced builder who wants to get his/her feet wet with SMT.

Here are the specifications (copied and pasted from Jason’s site) -

Frequency Range: Approximately 7.030 to 7.034 MHz (at +13.7 VDC power supply)
IF Bandwidth: Approximately 400 Hz
Current Consumption: 25 mA (at +13.7 VDC power supply)
Power supply: +9 VDC to +14 VDC
MDS: -123 dBm
3rd Order IMD DR: 84 dB
IF Rejection: 74 dB
Image Rejection: 67 dB
PCB dimensions: 70 mm x 100 mm
Antenna Connector: BNC
DC Power Connector: 2.1 mm barrel jack
Phone Jack: 3.5 mm stereo
Key Jack: 3.5 mm stereo
Muting, sidetone (user enabled), T/R switch, external VFO port included

More info here on Jason’s blog.

The CRX1 is not available as a “proper” kit yet but instead of selecting beta testers, as he has done in the past, Jason is selling 8 beta kits on his website for the sum of just $29. Because it comes with minimal documentation, it is only recommended for experienced kit builders. I have built 3 of Jason’s beta kits before and can testify that if you are good at soldering and know how to follow simple instructions, you’ll be fine. The beta documentation probably won’t give you a lot of hand-holding, but if you’ve done this sort of stuff before, you won’t have any problems.

If you’re in the mood for building something and have $29, this sounds like a good idea to me.

NOTE – I just noticed that the Etherkit store is now out of stock of the CRX1 beta. Hopefully we won’t have to wait too long for the production version of the kit.

March 25, 2013

The First CC1 to CC1 QSO – and a QSL as a Memento

Filed under: Amateur Radio,Ham Radio,QRP — AA7EE @ 7:17 pm
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I made my first ever QSO with the CC1 beta a week or so ago. It was with Jason NT7S (the designer of the CC1 and proprietor of Etherkit) and on top of that, it was the first ever CC1 to CC1 QSO. Very exciting!  I was hoping to have been the first ever QSO Jason had with his CC1. That honor actually went to WA0JLY, but I did get to be Jason’s 2nd QSO.

He was recording video of the QSO, which is up on his website if you want to take a look, though I am rather embarassed by my sending.  For some reason, I hadn’t plugged the paddle into the jack on the CC1 properly, and when I came back to Jason, the paddle went nuts and wasn’t sending what I wanted it to at all. I finally discovered the error, plugged it firmly into the jack and continued with the QSO. Jason for his part, (due also to nervousness at our historic QSO I’m guessing, just like me,) wished me 71 at the end of our brief exchange.  I like that! As I pointed out to him, 71 is like 72, but even better.  From now on, whenever I QSO with NT7S, I am going to sign off by wishing him 71. Perhaps that could become the default sign-off for any CC1 to CC1 QSO’s in the future? He also told me that my mess-up in sending due to not plugging the paddle in properly is one of those things that help create a narrative to remember these occasions with. Well, I guess so :-)

I don’t normally collect QSL cards, but some are special. This one from Jason is one of those in my collection that have great meaning.  In the early days of radio a QSL, instead of being seen as merely the final courtesy of a QSO, was the much-desired proof that a hard-worked for contact had taken place.  The early hobbyist would labor hard building his entire station, and spending many hours adjusting and tweaking in order to make contacts with other amateur stations. QSL’s were highly-prized pieces of proof that validated the work of the experimenter. I got some of that feeling on receiving this card from Jason -

This, in my opinion, is a QSL in the best time-honored tradition of amateur radio.  I’m running off to Fedex Kinko’s this morning to do a test-print of the custom QSL I’ve designed for my CC1 beta and hope to be spotting myself on QRPSpots later this week once I repair the final that I fried. I’m still not completely sure what I did, but it most likely had something to do with a stray clipped component lead or metal screwdriver :-)

March 21, 2013

The Etherkit CC1 1st Beta – A Trail-Friendly QRP CW Transceiver

About a year and a half ago, I posted that I had completed the first beta version of the Etherkit CC-Series QRP CW Transceiver.  It was a neat little rig, with low RX power consumption (of the order of 50mA – a bit less, I think), full DDS VFO coverage of any one HF band, a built-in keyer with memories, RIT and XIT, as well as firmware that could be updated at will with a simple AVR ISP programmer (you can get them for around $20). It also used a lot of SMT devices, and was my first serious project using these tiny parts (the KD1JV Digital Dial was the first).

My CC-20 beta worked, and I made quite a few QSO’s with it, including some DX. It wasn’t perfect though. The DDS VFO had some in-band spurs, the TX/RX switching produced a thumping sound, the input and output of the crystal filter weren’t as isolated as they should have been, you could hear some low-level processor noise on the receiver audio,  and the sidetone sounded a little rough too.  Although that sounds like a long list of woes, I think that anyone who designs circuits is used to tackling these kinds of issues one by one, until the dragon is slain. We (by which I mean Jason NT7S, the man behind Etherkit) did manage to improve the isolation of the crystal filter by a fairly good amount during this beta build.

Then he came out with the OpenBeacon kit and the EtherProg.  I knew he hadn’t forgotten about the CC-series, but I’m thinking he wanted to get a few other kits up and running before coming back to tackle it again, which he duly did.

The rig has been renamed the CC1 and although it retains the same basic architecture, there are a number of changes and upgrades to the design. It is still a monoband QRP CW HF transceiver (available in your choice of band) with an output of 2 – 3W (depending on the power supply), and it still has a DDS VFO (tuned with a real knob!) that covers the entire band, as well as RIT and XIT (useful for working split), freq readout in morse code and a built-in keyer with memories. The firmware is still also upgradeable via an AVR ISP programmer.  Although at this stage in the development it has not yet been implemented in the firmware, Jason thinks it should be possible to include APRS functionality and WSPR too. That’s quite a lot for a rig that is not much bigger than a pack of playing cards.

The beta kit arrived in a Priority Mail flat-rate box (what a neat sight on top of my mailbox!)  The enclosure is to the left, in the middle was the bag of parts for the EtherProg (a separate Etherkit product which can be used to update the CC1 firmware). The big bag on the right is the bag of parts for the CC1 -

The CC1 parts bag opened up to reveal the inner packaging.  The bag containing the bigger parts has been opened and those parts dumped into a mint tin.  The EtherProg, as I mentioned, is a separate Etherkit product and is available now, but I’ve included it in this photo. You can see the board slid partially into the enclosure -

A view of the underside of the board. Our beta kits had the microcontroller pre-installed. Currently, this was the only way Jason could supply it to us flashed with the firmware, but regular production kits will not have this IC pre-installed (it will have the firmware already flashed though) -

In true Etherkit spirit (the phrase “Open Source Amateur Radio” is on their home page), the beta testing forums are open for anyone to view here, and the forum for the CC1 beta is here. Only beta testers can post in these forums, but anyone can post in the product support forums which are here (you have to register first.)  The CC1 beta forums include schematics and an assembly guide which, although not final of course, will be of interest to anyone who might have an interest in the kit when it becomes available.

A couple of days of soldering, and the receiver section (which is about 85% of the circuit) was finished. Alignment consists of peaking 2 trimmer caps in the bandpass filter, and adjusting the BFO so that the wanted signal is in the center of the passband.  The passband for my filter is not flat – there is a definite peak in the response,  so I adjusted the BFO to place the wanted signal at the peak of the filter curve.  I already had a noise source that I had built to adjust the filters for my K2, and Spectrogram on my computer (for the same purpose) so I used these to adjust the BFO frequency.  Both the noise source and the use of Spectrogram are detailed here. With the receiver aligned, I have now spent every evening since just listening to it. I keep looking at it and thinking, “That little thing is a radio?”

Here’s the CC1 board with the receiver section completed -

You can see the GPS connector at the left-hand side of the board (the rear) immediately under the green key jack -

The onboard connectors are really great. They save a whole lot of hassle with wiring, and make it a lot easier to run the rig on the bench before putting it in an enclosure. In the following picture of the underside of the board, you can see U4, the 50Mhz master oscillator and to the right of it, U5, the DDS VFO chip. On the right-hand side of the board in the center, is U1, the NE5532 AF amplifier (I just saw a cat hair lying on top of U1 – those things get everywhere).  You can also see the space for U2, the transmit buffer -

At first, I thought the receiver wasn’t functioning correctly, because on attaching an antenna, I heard only a very faint increase in background noise. I tweeted to Jason and informed him as such, as well as posting to the other beta testers in the forum.  My theory was that the AF amp had low gain.  As it turned out, it was a combination of the bandpass filter being way off it’s peak, and the initial BFO freq placing the signal fairly well outside the passband of the crystal filter. Had I thought to peak the trimmers before jumping to conclusions, I would have realized that all was well.

The receiver was sounding good. The DDS spurs that were present in my CC-20 beta are no longer an issue.  The crystal filter has better isolation – there is still some room for improvement, and that will be improved further before it comes to market – in fact, Jason just suggested a circuit change in this direction that beta testers are implementing as we speak. The TX/RX switching is very smooth and the sidetone sounds nice. There is a sharp leading edge on the sidetone waveform which gives a clicking sound, but that will just require some simple shaping, which, once again will be taken care of in the production model. EDIT - another blog, and also a discussion in a Yahoo groupo, seem to have misread my last statement as meaning that there are key-clicks on the transmitted signal.  This is NOT the case. The transmitted signal sounds nice. I was referring to the sidetone only, which is a simple thing to take care of.  I emphasize also that this is a beta,  and we will most likely be taking this little rig through another beta before it goes into production. The other issue, the processor noise that was present in the audio, is vastly reduced and by the time you read this, will most likely be cured altogether, as Jason just re-wrote the firmware, which I am waiting to apply to my beta.  Things are looking very good for this little rig.

A couple more views of the board at this stage, before we move on -

Having confirmed that the receiver is working,  the final push was on to build the transmitter and complete the rig.  It didn’t take long – just the installation of 12 parts and 2 more toroids to wind.

Here’s the completed board, before installation in the enclosure -

The world of SMT seemed like a closeted world of intrigue and mystery before I built my first project using them.  I had read web sites detailing the use of solder paste and hair dryers, or toaster ovens for soldering these tiny little parts.  It was a while before I realized that you can actually solder them the good old-fashioned way – with a soldering iron and a roll of solder.  I pick up resistors and caps and place them close to their final resting place on the board with a fine pair of needle-nosed pliers. Then, with a small jeweler’s screwdriver, I gently nudge them into their exact position on the pads. While carefully holding the part down with the tip of the screwdriver, I tack-solder one end in place. Then I solder the other end, and go back to the first end to properly solder it.  I use a 1/32″ chisel tip and 63/37 .02″ solder with a mildly active rosin core.  0.015″ solder would be even better, as it’s easy to apply too much solder (which is where a good-quality de-soldering braid, such as Soder-Wick, proves invaluable.)

IC’s with fine lead pitch are a little trickier. The NE5532 AF amp was relatively easy, as the leads are far enough apart to solder them individually. Needless to say, a very clean and well-tinned tip is vital. I wipe my tip on a damp rag and tin it before every joint – unless I’m soldering a number of joints in quick succession one after the other, such as with IC’s.  The AD9834 DDS chip has leads that are too closely-spaced to solder them individually. The technique that I learned from Jason involves soldering all the leads on one side with a big wodge of solder, paying no attention to whether the leads are bridged together with solder.  Afterwards, you clean up the solder bridges with de-soldering braid and a larger iron tip. A larger tip is useful here because you can wick up the excess solder more swiftly in order to avoid destroying the chip. Jason posted a good description of how to do this in the assembly guide.  Search for U5 on that page and you’ll find the description, along with a picture.  Flux is said to be very helpful here.  I managed it with no extra flux (other than that in the solder) , but plan on getting some for future use.

The CC1 is billed as a trail-friendly rig, and the kit will come complete with a pre-drilled enclosure with silk-screened front and back panels.  The enclosure we received with our beta kits is the exact same enclosure that will go out with the kits, with the exception that ours weren’t drilled or printed.  So the following pictures represent roughly what the final CC1 will look like, without the silk-screened panels. There might be a slight adjustment in the spacing of the controls before the final production model too.

Firstly, this one’s for size comparison with my CC-20 beta -

The board slides into rails in the side of the extruded aluminum case and is held in place by the nut on the BNC connector at the back.  Here’s a couple of front views without the front panel -

Man, is this thing a beaut or what?

I’m very fond of this little rig. I’ve only made 1 QSO with it so far (with Jason NT7S) but have spent every evening listening to it. It’s great to have the earbuds in, listening to 40M on this diminutive little transceiver while working.

I’m hoping to get some audio up at some point, but it may take a while. If you’re wondering when you can get one of these, well, it’s still in development but at this point I think it’s safe to say that it will be coming out. I do know that Jason NT7S is a perfectionist and won’t release it until he feels it’s truly worthy, and all issues have been thoroughly worked out. The design is already very close to where it should be and there’s a great momentum behind it, but we still have a 2nd beta to go through  Stay tuned and we’ll keep you posted.

July 27, 2012

Using the NM0S Hi-Per-Mite Filter From 4SQRP To Make A Simple 40M DC CW RX

When 4SQRP brought out a version of the David Cripe NM0S-designed Hi-Per-Mite Filter, I noticed that it could be configured to give up to 50dB of gain. Like many others, I’m sure, my next thought was that it would make the process of building a simple direct conversion receiver even simpler. I decided that at some point, I needed to use this little filter board as the audio chain in a direct conversion receiver for CW.  I wanted to see for myself how it would sound.

In the meantime, my preoccupation with direct conversion receivers continued, as I embarked on building a G3WPO/G4JST DSB80. The receiver in that DSB rig uses an SBL1-8 DBM. That particular mixer package is out of production, but I used an ADE-1 and was pleasantly surprised by the receiver. I had some problems with the TX section, so put it aside and started building a ZL2BMI DSB transceiver.  I’d known about this little rig for a while from the pages of SPRAT, but a comment on Twitter from NT7S encouraged me to have a go at building it. The receiver is a simple NE602/LM386 combination with just a single-tuned filter on the antenna input. Of course, the receiver is not THAT simple, as each chip contains more complex circuitry, but the schematic at the chip level looks almost too simple to work.  As with the DSB80, I had problems with my ZL2BMI rig transmitting a sizeable residual carrier, but was surprised that the receiver sounded pretty good. The seed was sown…..

The ZL2BMI DSB rig was actually only the second time I had built an NE602/LM386 direct conversion receiver. The first was about 20 years ago when I bought a kit for the Sudden receiver on 20M. At the time, I wasn’t that keen on it and it soon ended up in pieces. I’m not exactly sure why I wasn’t taken by it, but I think it was a combination of factors. Firstly, I was living in an apartment in Hollywood with no outdoor antenna and was using just a short length of wire indoors as an antenna. It’s also highly possible that band conditions weren’t great, but I just remember not hearing many signals and also not liking the fact that a half-turn of the variable capacitor covered the entire 20M band. Because of this one not so great experience, I have since harbored a bias against using NE602’s in direct conversion receivers, an attitude that I now realize was unfair.

After achieving only partial success with both these rigs but enjoying the fact that the direct conversion receivers in both of them worked quite well, I wanted to build a simple receiver and use the Hi-Per-Mite kit that had been sitting patiently on my shelf for the last few weeks.

Look at the schematic for any NE602/LM386 DC receiver, and they are almost all the same, differing only in whether they use a crystal, ceramic resonator, or free-running VFO for frequency control, whether they have a single-tuned or double-tuned antenna input filter, or whether they use a differential or single-ended audio output.  The circuit is so simple that there is only so much room for variation, but there were a couple of things I had in mind for my mine.  While the receiver portion of the ZL2BMI rig only has a single-tuned filter on the antenna input, I wanted to do what G3RJV did with the Sudden, and place a double-tuned filter there. It’s an easy thing to do, and living in a built-up urban area, I have a lot more RF around me than ZL2BMI does when he’s using his rig in the bush, so a bit of extra bandpass filtering certainly couldn’t hurt. The other decision to be made was the method of frequency control. I was curious to see how the internal oscillator in the NE602 would work as a free-running VFO.  My apologies to you folk who have built umpteen simple NE602-based receivers and have-been-there-and-done-that.  I guess I need to get this out of my system! Another thing that I had seen in other circuits but hadn’t tried was the use of a 1N4001 diode as a varactor. Some call it the poor man’s varactor. Sounds like it was custom-made for me!

So that was my configuration – double-tuned input filter (just like the Sudden) and a free-running VFO tuned with a 1N4001 diode.  From what I’d read, I knew that I should be able to get enough capacitance swing from the 1N4001 to cover at least the bottom 30-50KHz of 40M. Here’s what I ended up with:

There’s nothing original in this schematic  but as you’ll see soon, it did turn out quite well, so I decided to name mine “The Rugster” after my cat, whose full name is Chloe-Rug, but who gets called several different variants of that name, of which “The Rugster” is one.  For the input bandpass filter, I used the vales of L and C that are used in the GQRP 40M Sudden Receiver. The pre-wound inductors in that design have a value of 5.3uH. I decided that I wanted to use T37-2 cores, so I used the calculator on W8DIZ’s site to figure out that I’d need about 36 turns on a T37-2 core to give 5.3uH of inductance. I fiddled around a bit with the values of the parallel fixed capacitors before settling on 47pF for those. I had originally thought that a higher value of around 68pF should work, but that didn’t put the peak of the filter somewhere in the mid-range of the adjustment of the trimcaps.  Some experimentation revealed that 47pF fixed caps achieved this.  Your value may vary depending on what value of trimcap you are using.  For the VFO inductor, I found a design for a 40M DC RX on the internet that was tuned by a 1N4001, noted the value of the inductance, decided that I wanted to use a T50-7 core (for stability) and once again, used Diz’ site to calculate the number of turns needed.

When building receivers, I like to start with the audio chain first. It’s quite affirming to be able to touch the input and hear that reassuring loud hum and mixture of AM broadcast stations in the speaker! So I got out the 4SQRP Hi-Per-Mite kit. Close inspection of the PCB revealed a small problem that was easily remedied. There was a very, very narrow copper trace connected to the ground plane that had been bent so that it was contacting the input pad.  A DVM test confirmed that the input pad was shorted to ground. I didn’t take this picture until I was part of the way through removing the offending trace, but you should be able to see the problem:

A minute or two with a sharp craft knife and that pesky little trace was history. Here’s the finished board:

The only thing that prevented me from putting this kit together even more quickly was my own compulsion to solder the components into the board so that they line up as straight as possible. The holes for some of the capacitors were a bit larger that they needed to be so that if you just plug them into the holes and solder, they’ll be a bit off-square. It’s not a big deal, and most builders won’t be bothered by it, but I just can’t control my OCD tendencies sometimes. Anywhere, I finally got there:

Although with modern low-flux solders, there is no need to remove the flux, it sure does make a board look nicer. I recently started using flux remover on my boards so that I can show off the underside too. At the suggestion of W2EAW, I apply it with a cheap plumber’s flux brush obtained (for 19c) from the local hardware store. Look at that nice clean board!

Trader Joe’s sells Green Tea Mints in a clear-top case that fits the Hi-Per-Mite board well if you’re looking to use it as a stand-alone device. There’s also room for power and in/out connectors (though you might need to cut off the top corners of the board in order to make room for the connectors.)  The tin in this shot had been knocking around my bench for a while, so the clear-top is a bit scratched up, but you can see the potential:

The next step was to build the direct conversion receiver with the NE602 and some of W1REX’s MePADS and MeSQUARES. The most frequency-sensitive part of the VFO circuit was built ugly-style, with the help of a 10M resistor for a stand-off, to help the stability. I don’t have any pictures of the board without the Hi-Per-Mite audio filter/amp added, so here’s the finished board. In the earlier shots, you can see the VFO toroid before I decided to slather it in hot glue in a bid to make it a bit more stable. There is only one component in the final receiver that I missed from the schematic, and that is a 1N4001 diode in series with the 12V supply for reverse-voltage protection.  I’ve blown too many fuses in my shack supply to not use these little fellows in the future :-)

Another shot from basically the same end of the board, showing the input bandpass filter on the left, VFO toroid on the left at the back and the DC input circuit nearest you on the right (reading from right to left, you see the reverse-polarity protection diode,  10uF input smoothing capacitor, 78L08 voltage regulator, and the 0.1uF DC output bypass capacitor. I’ve had those green trimcaps for a long time and it was time they were used. They don’t take solder well (I think I got them from Radio Shack about 10-15 years ago) but it seemed a shame not to use them in something:

Here you can see the varactor tuning circuit built ugly-style just to the left of the VFO toroid. The 3 connecting cables are for the AF gain pot (which is connected in place of R11 and R12 in the Hi-Per-Mite, as per the Hi-Per-Mite instructions), multi-turn tuning pot, and AF output jack. I’ve used lavalier mic cable that I bought from a local pro-audio store. It has 2 inner conductors shielded by a single outer braid and is very flexible, which makes it useful for wiring up small radios.  RF connections (which you’ll see in later photos) will be made with Belden 8216 coax:

At this point, I was very gratified to discover that the receiver actually worked, and seemed to work quite well too. That fact gave me enough inspiration to start building an enclosure to house it in.  The next shot isn’t ideal, as the back of the case is a little out of focus. You’ll notice that the front, and the two bolts sticking up on the right side are in focus, but the back of the case (and especially the bolt at the back left) isn’t. When I realized this, I was too far along installing the board to go back and take another shot and besides, sometimes I just have to control myself and keep forging ahead:

A view of the board installed in the case, with the lid:

A closer view from the top, in which you can see the VFO toroid now doused thoroughly in hot glue.  I’m not sure if it helped the long-term stability at all, though it did help to make the VFO more resistant to physical shock. Another way of securing the VFO toroid in a vertical position would have been to drill 2 small holes in the PCB and use a small nylon tie:

The coax that leads from the 1K log RF attenuator pot to the board is a little long, and that is because the one you see in the photos is a 10K linear pot. It was all I had at the time of building.  I am going to swap it out for a 1K log pot when the next order arrives from Mouser in a few days, and kept that lead a little long in case I need to chop some of the end off when changing the pot out.

Here’s another view of the innards. I am quite pleased with the way this little receiver turned out. You can see one of the 4 brass nuts that are used to secure the lid to the rest of the case. I use brass, as I can solder to it with regular solder. When placing the nut, and before soldering, I screw the 4-40 machine screw through the side of the case into it so I know the nut is in the right place.  If I were to get a little over-zealous when applying solder and accidentally get solder on the screw it wouldn’t stick, as the screw is made of stainless steel:

This is what The Rugster looks like in her case with the lid on:

If you look closely at these pictures, you’ll see that the PCB panels don’t line up perfectly and that the edges are just a little rough.  I am somewhat detail-oriented, but I am not a craftsman by any means, and I know my limits.  I made a conscious decision not to spend a lot of time filing and sanding edges. After making deep scores in the board and breaking it, I ran the edges across a file on the bench a few times and left it at that. Good enough is good enough in this case, and it’s certainly good enough for me.

A view of the underside:

I’ve spent a few evenings listening to it and most of the signals that my K2 could hear, this little receiver could hear almost as well. With the very weak signals the K2 won, of course.  A small part  of this could be due to the fact that the DC receiver, even with it’s 200Hz-wide filter, is still listening to double that bandwidth, as it is hearing on both sides of the local oscillator.  Naturally, I expected my K2 to be the better receiver (duh!) but was really surprised at what an enjoyable experience listening to this one is for such a simple circuit.  As expected, it does overload in the evenings, but all I have to do to get rid of the breakthrough is to adjust the RF attenuation pot back a little from “full gain”, and the breakthrough disappears.   Elecraft use an NE602 in the front end of the K1, and it has an attenuator for the same purpose. I’m not sure whether the breakthrough is from strong in-band amateur signals or from AM broadcasters – it’s actually hard to hear the content due to the narrow bandwidth of the Hi-Per-Mite. One small adjustment of the RF gain pot and it’s gone – then I just bump up the AF gain a bit to compensate. Volume is enough to drive my MFJ-281 ClearTone speaker.  I normally like to listen to CW with a 500Hz note, but because the response of the ClearTone drops off below 600Hz, I kept the Hi-Per-Mite filter at it’s design center-frequency of 700Hz, and the speaker sounds good. EDIT – If the AM breakthrough is from signals in the 550 – 1700KHz AM broadcast band, which I strongly suspect that it is, a simple high-pass filter with the cut-off set somewhere around 2 or 3MHz should work wonders to eliminate this.

The fact that the tuning rate is quite low helps a lot in the enjoyment of this receiver too.  The 10-turn pot covers 6999KHz – 7051KHz giving an average tuning rate of about 5KHz/rotation. The VFO shifts in frequency very little indeed when  the receiver is knocked or moved. Drift is not great, but manageable.  Drift in the first 10-15 minutes is only slightly worse than after that initial warm-up period,  so I’ll give you the results from switch-on, which were 90Hz drift in the first hour,  140Hz drift in the second hour, and 110Hz in the 3rd hour. All the drift was downward – there was no upward drift at all. The drift was steady, and with a little bit of compensation, I think those figures could be improved upon quite a bit. However, for casual listening (and this is all I am going to use this for) it is adequate.

This receiver is certainly not perfect, but considering it’s just an NE602 and an LM386 (oh – and a quad op-amp IC for the filtering), it’s not bad at all.

Thanks Dave NM0S and 4SQRP for this neat little audio CW filter kit.

Here are a couple of videos that I just made of The Rugster. Please excuse the poor video quality – it’s an old, cheap camera:

This one is a little shorter:

July 2, 2012

The DSB80 Part 2 And A New Addition To The Shack

Filed under: Uncategorized — AA7EE @ 7:40 pm
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I did make some progress on the DSB80 a couple of weeks ago and then put the project aside.  I became a bit sidetracked by other things, some of them non-radio, so want to provide an update in case the DSB80 project gets shelved for a while.  I received a wonderful e-mail from Frank Ogden G4JST, co-designer of the DSB80. He sent me a picture of his prototype DSB80 with my letter to him alongside. What a thrill! He said that he powered up this fine little rig, and it was still putting out 4W of DSB on 80 with fine audio and a stable VFO:

Frank told me that when he designed the DSB80, he scratched the circuit out on a piece of paper and sent it straight to Tony G3WPO, who came up with the PCB design. It was never bread-boarded.  Amazing!  Frank has many happy memories of making many QSO’s with southern England and northern France from his brother’s boat on this rig.  As I’ve mentioned before, the DSB80 I built from the kit supplied by WPO Communications worked fine.  How I wish I still had it :-)

If you recall from the last post, I had been having some problems with the buffer amp in the VFO not buffering too well.  Jim K4AHO suggested that I capacitively couple the output of the VFO to the input of the buffer instead of coupling it resisitively. He also suggested a high-value resistor from the gate of the buffer JFET to ground to act as a self-biasing resistor. This cured the problem nicely – on terminating the output of the buffer with a 51 ohm resistor and touching it with a screwdriver, there was no noticeable shift in VFO frequency (unlike before). The output from the VFO transistor was a nice sine wave:

Here’s the output from the buffer transistor when terminated with a 50 ohm resistor:

The above waveform is about 0.9V pk-pk which, by my calculations, across a 51 ohm resistor, translates into around 2mW – just +3dBM, which is a little low for a level 7 diode ring mixer. Also, that waveform – I don’t know how important it is that the VFO buffer outputs a clean sine wave into a 50 ohm load, but I’d sure like to see it.

I decided to press on and see if I could finish the transmitter. This is where I got:

If you saw the earlier iteration of this board from a previous post, you’ll see that I have removed the on-board VFO.  In it’s place is the mic amp for the TX section. I also built the TX driver and TX final. The TX seemed to be generating a pretty nice-sounding DSB signal from the driver using a 2N3904 in place of the originally-specified BC238 device. G4JST very kindly offered me a VN66AF (the device originally specified for the final) for my experimenting, but I wanted to adapt the circuit to use the commonly available IRF510. Heck – you can even get ‘em at Radio Shack.

I’ve had a couple of problems with the IRF510 final. The first was solved with the help of NT7S. Jason did a bit of brainstorming with me and we found that there is a choke in the collector circuit of the driver transistor that is designed to resonate with the input capacitance of the MOSFET final.  It turns out that the input capacitance (Ciss) of the IRF510 is in the range of 135 – 180pF, while that of the VN66AF (the final in the original DSB80 design) is around 50pF. Changing the choke from 33uH to 12uH increased the output from the final from 3/4W to something like 2 – 2  1/2W (I didn’t write it down). However, I also noticed that the rig was putting out significant carrier in the absence of modulation. I don’t think this was due to poor carrier suppression – rather due to a spurious response somewhere in my circuit layout.

This is where I’m at with my version of the DSB80. The receiver sounds good and has given me fresh inspiration to build some more direct conversion receivers. I almost wish that I had not built the TX section, as I don’t do a lot of transmitting on phone anyway, and this is the only part of the circuit I’ve had a few problems with! I’m sure that it’s my layout, or my use of different active devices, as my original kit back in 1983 worked well.

So my DSB80 board is sitting up on the shelf for the time being while I give it a rest.

By the way, there’s a new addition to the shack, which you may have noticed from the pictures above. It’s a Tektronix 465 oscilloscope. A very generous local ham gave me his old Tek 465.  I’m not sure whether he wants to remain anonymous or not but he knows who he is, and to say that this was a generous gift is a huge understatement. Thank you very much – you know who you are!

May 28, 2012

The Etherkit OpenBeacon – A Very Versatile Programmable MEPT

etherkit’s OpenBeacon is the first kit to be offered by proprietor Jason NT7S and I think it’s a good one for him to open up with.  Sure, it’s not the first QRSS transmitter kit on the market but unless I’m missing something (and I don’t believe that I am) it is the most versatile one offered to date. Here is a list of all the modes that it can transmit:

  • Dual Frequency CW with 3, 6, 10 or 120 second dits (3 second DFCW is the most commonly used QRSS mode on the HF amateur bands and is the default mode programmed into OpenBeacon)
  • QRSS CW with 3, 6, 10 or 120 second dits
  • Regular CW (you choose the speed)
  • Sequential Multi-Tone Hellschreiber
  • WSPR – billed as an experimental mode, but I’ve used it with success
  • Glyphcode – a mode that uses Hellschreiber to generate dots and dashes
  • A special calibration mode that is useful for setting the center-frequency and bandwidth of your transmitted signal

There are no jumpers for mode-switching. It’s all done with the software client that is available for Windows, Linux and Mac OS X. This software control opens the door for anyone who wishes to come up with their own code to control OpenBeacon (and hopefully share it with other users in the etherkit OpenBeacon forum.)

First things first. Here’s what you get:

In this shot, I took the rather good-looking PCB out of it’s wrapping so you can see it a bit better:

Construction is straightforward. If you’re new to kit assembly and the art of soldering, it may take a little longer to figure out. The usual guidelines apply – identify all the parts, and don’t solder anything into the board until you’re sure that it’s the right part, and you’re soldering it in with the correct orientation. There are useful checks included at several points during the build and after the first stage has been completed, you get to connect the board to a USB cable and see your computer recognize the OpenBeacon. If you’re running Windows, you’ll need to install a driver before this can be accomplished, but it’s reassuring to have the project recognized by your computer at such an early stage of construction.

Here’s the finished board:

And another view of the completed board:

Apologies – I forgot to include a rule in the pictures to give you an idea of the size of the board, so for the record, it measures 70mm x 90mm.

One thing I really like about OpenBeacon is the on-board connectors. Once you’ve finished assembling it, you can plug in a USB cable and an antenna, program it with your call-sign and you’re on the air. If you want to run higher RF output power than the approximately 40mW max you get from USB power, then you can plug in DC power to the on-board DC power connector and get about 300mW from a 13.8V supply. These kinds of QRSS transmitters are often not installed in conventional enclosures anyway, so it’s really good to be able to begin experimenting with OpenBeacon straight off the bat.

This is a bit gratuitous, but here’s a really close-up view of part of the board:

If you don’t already have a QRSS viewer, Argo is the easiest to set up and get going with.  OpenBeacon is already set to transmit in QRSS3 as the default mode, but you will need to program it with your callsign by downloading the client for your particular operating system and following the directions on the etherkit site. If you have problems with any of this, Jason NT7S, or one of the etherkit forum members should be able to help you out.

Of course, the first thing you want to do with a transmitter like this is to see what your QRSS signal looks like on your own viewer:

The very next thing was to see what my callsign looked like in Multi-Tone Sequential Hellschreiber:

You’ll notice that the vertical scale on my Argo screen captures is calibrated with the frequency.  To achieve this, you’ll need to accurately calibrate your receiver so that you can set it to 10139 KHz. In my case, I know that after it has been running for a while, my K2 receives at about 10Hz lower than the dial frequency, so to receive on 10139 KHz I set my K2 to 10139.01. The next step is to enter an offset of 10139000 in the calibration menu and you’re all set. The QRSS band normally runs from 10140 to 10140.1, so a carrier in the center of the QRSS band will produce a tone of 1050 Hz in the speaker of your receiver.

One thing that’s very important to remember if you run into any difficulties during assembly -

Incidentally, before anyone suggests that I was illegally radiating a sginal without proper identification, the above screen capture was taken as a result of outputting 5mW from the OpenBeacon into a 50 ohm dummy load – not too much radiating was taking place.

I did run OpenBeacon for one night in QRSS3 mode but wasn’t able to find my signal on any grabbers.  It was only one night and I was, after all, running just 5mW RF output (sucker for punishment here). I’ll be trying it again soon, but at the time I was keen to forge ahead and try the WSPR experimental mode.  I did briefly have a go at figuring out Glyphcode but either the instructions in the Client Software Useage Guide on the etherkit site weren’t clear, or I was being a bit thick.  It could well have been the latter. I’ve no doubt that Glyphcode isn’t hard to program but at the time, was more immediately interested in playing around with WSPR on OpenBeacon, so I hoofed it on forward to that section of the online guide.

To transmit a WSPR signal with OpenBeacon, you first have to load the buffer with the appropriate code. I downloaded wsprcode.exe and placed it in the root directory of my PC.  This is a description of what I did on my PC running Windows. Your mileage will vary if you are running any other OS. In DOS at the command prompt I typed wsprcode “AA7EE CM87 7″  You’ll need to do the same with your callsign, 4-digit locator and power level (in dBM). wsprcode will output the data symbols, sync symbols and channel symbols for your particular data – all you need is the last set of characters – the channel symbols.  Cut and paste this data into a simple text editor (I used notepad on my PC) and edit it to erase all spaces between characters as well as any carriage returns so that all you are left with are 162 characters in a continuous string with no spaces (or anything else) between them.

The next step is to program the buffer of your OpenBeacon with the WSPR code. Using the OpenBeacon client software, the command for this is openbeacon wsprbuffer “flangesprocket” where flangesprocket represents the string of 162 channel symbol characters.

All that remains is to place OpenBeacon in wspr mode, adjust the transmission bandwidth to 10Hz, and the frequency to put you in the wspr band, and manually trigger OpenBeacon (either with S1 or through the client software) at the beginning of an even-numbered minute. OpenBeacon will transmit your wspr signal for the required 1 min 50 seconds.

Here are the unique spots representing 2 evenings of operation:

Date Call Frequency SNR Drift Grid dBm W
by loc km mi
 2012-05-28 02:36  AA7EE  10.140138  -17  0  CM87ut  +7  0.005  K7LG  DM04se  530  329
 2012-05-28 02:20  AA7EE  10.140102  -23  0  CM87ut  +7  0.005  VE6PDQ/1  DO33fl  1867  1160
 2012-05-27 05:24  AA7EE  10.140108  -22  -1  CM87ut  +7  0.005  K7MSC  CN76wv  1021  634
 2012-05-26 07:20  AA7EE  10.140125  -19  0  CM87ut  +17  0.050  W7WKR  CN98pi  1179  733
 2012-05-26 07:10  AA7EE  10.140144  -16  0  CM87ut  +17  0.050  W5OLF  DM78hb  1482  921
 2012-05-26 06:20  AA7EE  10.140138  -22  0  CM87ut  +17  0.050  K7UEB  DN06tb  973  605
 2012-05-26 05:34  AA7EE  10.140129  -26  0  CM87ut  +17  0.050  VE6PDQ  DO34ir  2000  1243
 2012-05-26 04:36  AA7EE  10.140108  -8  0  CM87ut  +17  0.050  KC6KGE  DM05gd  390  242
 2012-05-26 00:08  AA7EE  10.140114  -16  0  CM87ut  +17  0.050  N6RY  DM13id  688  428

Not a lot of unique spots, but I was only running 5mW.  The first spots were reported as being 50mW, but this was my mistake – I was actually running just 5mW and corrected the wspr code as soon as I discovered my error. I decided to stick with an output power of +7dBM as that is the power I feed my diode ring mixers, and it just slightly blows me away that my signals were decoded by VE6PDQ over 1200 miles from me with the same power that my local oscillators put out. Quite amazing. I have no doubt that I’ll achieve even better DX if I keep at it.  As I have developed an affinity for level 7 diode ring mixers, running a power output of +7dBM from the OpenBeacon seems very fitting.

Now, as etherkit is an open source amateur radio company, I’m hoping that someone will write a routine to automatically trigger OpenBeacon when in WSPR mode. It definitely seems to work quite well in that mode.

This is where I stand with my OpenBeacon so far, and I think it’s the most versatile MEPT available in kit form. It boasts many different modes and speeds (as well as WSPR) and to change between them you don’t have to fuss around with wire jumpers. It’s all done in software, like many other things in OpenBeacon. This ability to control it in software, along with the wide variety of modes, and the open-source nature of etherkit make it, in my opinion, the ideal MEPT for a lot of users.

January 31, 2012

QRP CW WAS, KA0XTT and W0O, WBR Receiver, and NT7S To Give Seminar at FDIM

Phew – quite a headline there.  I suppose if I were a more organized blogger, I’d break this into several different topics and get several blog-posts out of it.  However, I’d like to get it all out of the way, and get this info imparted to you in one fell swoop, so here goes.

After completing the Norcal 2N2/40, I got to thinking that it would be really neat to achieve WAS with it – that would be QRP CW WAS on just the one band – 40M. I didn’t get close unfortunately, though I didn’t make a concerted effort either.  On completing the K2, all the other QRP rigs with the exception of the CC-20 were packed up and put into a box; I wanted the operating desk cleared and simplified so I could spend time with my precious new fixation – the K2. With that, the prospects of QRP CW WAS with the Norcal 2N2/40 faded somewhat, but I realized that with the multiband capability of the K2, achieving QRP CW WAS should be pretty straightforward – and it was.

In my entire amateur radio career, I have never won any kind of award – and I’ve been licensed since 1978.  This has been due mainly to very occasional periods of activity interspersed with longer periods of inactivity; a pattern of operating that I know I share with quite a few other amateurs. I’m also not a very competitive person, but it seemed that it was about time I qualified for something, and QRP CW WAS seemed like the obvious first choice.

Not much to say really.  I operate almost daily, and many of those QSO’s from normal operating provided QSO’s for WAS. Add in the odd contest here and there (the ARRL 10M Contest was very helpful, as was NAQP).  Predictably, as my list of states still needed got down to a mere half-dozen, Delaware and Rhode Island were in that list. Luckily, NAQP allowed me to nail both those states through QSO’s with WW3DE and W1WBB.  At the end of my last blog-post, I asked if anyone could give me a QSO with WV, as that was the last state I needed. Frank KA8SYV very graciously responded and did indeed give me a QSO with West Virginia.  It was quite fitting that the QSO with Frank was the one to complete my WAS, as it was he who bought my FT-817 back in June of last year.  We did try to make the QSO with his FT-817, but I couldn’t quite copy his sigs, so he went up to 100W, and the difference was like night and day. Luckily he copied the 5W sigs from my K2. Thanks Frank – your 40M loop was doing a fine job.  Not only was the personal connection with Frank a good reason for him being the final QSO of my WAS attempt, he has an excellent QSL card too, which gave me another reason to want a QSL from him. Here it is:

Frank said that so many people commented positively on that image that he had it made into a QSL. I love it! A few days after receiving it, a card arrived in the mail from John N8ZYA, for a QSO we’d had a few months earlier.  John noticed from my blog that I needed a confirmation from WV and sent me his card.  How did I miss that WV QSO when looking back through my log? Even more perplexing is that John and I have exchanged e-mails and blog comments before, so are well familiar with each other.  Aah well – better to have too many confirmations than too few. Thank you John.  For dog lovers, my Alabama QSO provided me with this QSL:

I now have all the contacts I need. I am waiting for one confirmation from W1SJ in Vermont, but his QRZ page states that QSL’s are generally answered 6 weeks after a contest, so I have every reason to believe that a confirmation from him is forthcoming. When it arrives, I’ll be able to apply for a WAS certificate from ARRL, or if I want to stick to my original goal of having a paper QSL from each state (and not just a combination of paper and LoTW) then I think there are one or 2 more states I need paper QSL’s from. However, they are all states with which I have enough insurance QSO’s so it’s not a problem.  I’m not sure if I will even apply for the certificate. I’ve already achieved WAS. Once the confirmation arrives from W1SJ, I’ll have confirmation that I’m in the log in 50 states for QRP CW contacts and that’s enough for me. Mission accomplished!

Yesterday morning, a QSL I’ve been hoping would materialize actually did. It was for a contact I made with special event station W0O in Frankenstein, MO on Oct 31st. What a fine card. I can’t think of a more fitting QSO on Halloween than with a station in Frankenstein. Thank you very much to the Mid-MO Amateur Radio Club:

The postmark on the envelope was equally impressive. Can you see the word “Frankenstein” spelled out in the tree branches?

Another QSL to arrive yesterday was this one from the fictional TV character Mike Baxter KA0XTT, played by Tim Allen in the series Last Man Standing.  In return for my QSL, the production team sent Mike’s QSL, autographed by Tim:

A group of hams on Twitter decided to send our cards in as a bundle together in the hope that our cards will all be displayed on the wall at Tim’s operating position in a future episode.  I suggested that they send their cards to me so that I could send them on their way, my reasoning being that as I’m in California, the last leg of the trip will be a day or two quicker. Here are the cards from our Twitter group before being bundled up and sent to Studio City:

N9VN and KE7JTU’s cards didn’t arrive for some reason. Perhaps they will be the subject of a QST article in a few decades along the lines of “QSL cards long considered lost finally arrive 30 years later”!

In other news, I was excited to be able to contribute some text and photos to the next edition of the ARRL book “Low Power Communication” written by Rich Arland K7SZ. The subject will be my build of the WBR Receiver, which has generated quite a lot of interest. Poor Daniel N1BYT must be getting a bit fed-up with the renewed interest in his excellent regen receiver design, 10 years after it was initially published in QST.  I noticed that his e-mail address has disappeared from his QRZ page and did wonder if he did it so that we’ll all stop bothering him with questions about the WBR! It will be the project for the group build at this year’s OzarkCon, a number of people have commented to me that they have also built, or are building, their own copies of the WBR, and at least 2 individuals/groups have expressed interest in making a kit of parts available, though I don’t know whether a kit will materialize. To this day, the post on this blog about the WBR is by far the most popular, consistently receiving more views than any other post. Thanks Rich – I have never had anything I’ve written or taken pictures of published in a book before, so this will be thrilling!

Last but very definitely not least, the news has just come out that Jason NT7S will be heading up a seminar at FDIM this year. While I know that he would be well-equipped to talk about the logistics of providing day-care for a toddler and a boisterous (yet affectionate) golden lab, while still managing to find time to design circuits and occasionally even operate on the air, the tentative subject of the talk will be the use of free and open source tools in the development of his products, but he may tweak the subject and content of the talk as time progresses.  If you want to learn about etherkit and Jason’s planned product line, FDIM this year will be a good place to be. He will also have a vendor booth.

October 23, 2011

A Cheap Yet Useful Capacitance Meter

I remember John AE5X blogging a while ago now about a cheap capacitance meter that read the capacitance values out in Morse code.  Some time later, on searching around online, I found a cool-looking and cheap meter  on Sparkfun. John blogged about this meter too. More recently, anticipating an upcoming need for such a device, I shopped around to see if I could find the one that SparkFun offers anywhere else. I found it for a little less money, so for $11 plus $5 shipping, a small bag of parts arrived in the mail from Amazon just a few days later.  I won’t show you what a small bag of parts looks like, as I’m sure you can visualize it yourself, but when I stuffed the parts in the board, here’s what it looked like:

I plugged it into a power supply (8 – 16V DC through a 2.1 x 5.5mm jack, which is a popular size) and well, there’s not much to say – it works. I tried a variety of different capacitors from a few pF to several hundred uF, and they all measured within their tolerances. The meter is auto-ranging, so all you do is plug the capacitor into the socket at the bottom-right of the board (the one marked J5) and read the value from the display. It will measure from 1pF to 500uF – a range that will encompass pretty much anything the home-brewer is likely to come across.

My motivation in getting this is my eventual desire to build a K2. The manual for the K2 recommends the use of a meter to check the cap values, and with a kit like that which has so many parts, I want to be armed in case any doubt exists as to the value of any particular capacitor.

In other news, Jason NT7S is putting in a lot of work solving issues with the first beta of the CC-series of kit transceivers and it looks like he has one of the major issues solved.  I’m very much looking forward to building another CC-series transceiver and then seeing as it becomes available to the public in kit form.  He’s aiming to put it on the market in January 2012.

Had a very enjoyable, yet all-too short QSO with KI6NTB Shin recently. Shin lives in Huntington Beach, CA because he’s a surfer and well, Huntington Beach is a very good place to live if you love to surf. Shin – it looks like you have a great life there – and living in a smaller community like Huntington Beach is definitely a great way to live in SoCal without living in the general sprawl that much of SoCal is.  Not that I dislike the general sprawl – I lived in LA for over 20 years and loved it. Shin reads  this blog – so hello Shin and thanks very much for the QSO.

October 18, 2011

A Trilogy With T32C – Thanks To The CC-20

Filed under: Amateur Radio,Ham Radio,QRP,Uncategorized — AA7EE @ 4:42 pm
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In the last post I reported that I had made contact with the T32C team on 40M with 4W from my Norcal 2N2/40, and also with 4W on 80M from my Tut80.  The goal was to make a contact with them on every band I have capability for here, which meant just one more band – 20M with the first beta version of Jason NT7s’ CC-20.  Last night I achieved that goal, and was surprised at how easy the mechanics of it was with this monoband QRP rig. What made it easy was Jason’s recent addition of XIT to the firmware. If you push and hold the tuning encoder in for half a second, on releasing it, you hear a morse code “R” in the headphones and the front panel LED lights, indicating that you are in RIT mode.  Holding it in for another half second gives you an “X” in the headphones, and the LED flashes, indicating that you are in XIT mode, giving you independent control over your transmit frequency.

Here’s where it gets neat. While in RIT or XIT mode, if you briefly depress and release the tuning button, you can listen on either your transmit or receive frequency, which is very useful for finding out where stations are calling during a split-frequency operation in XIT mode. Press the tuning knob once, and you hear an “R”, meaning that you’re listening on the receive frequency. Push it again and you hear a T, which means that you are now listening on the transmit frequency.  Also, while in RIT or XIT mode, pushing the FREQ/OK button (one of two front-panel pushbuttons) will trigger a readout of the frequency difference between your receive and transmit frequency in morse code. When operating normally, this button triggers a direct readout of the operating frequency. If you look at this new picture of my first beta version, you’ll see one addition; the front panel LED to indicate RIT/XIT mode. You’ll also notice that I forgot to install the screws on the side of the case for the photo. The screws have been off recently, as there have been several firmware updates while Jason fine-tunes the firmware:

It has been fun watching the CC-20 slowly take shape and for a compact and trail-friendly radio, I do believe this is about as full-featured as they come. This is not a final spec – that will have to come from Jason, but here’s a rough list:

*Rx current consumption ~ 40mA

*Tx output power 2W

*Full band coverage (14 – 14.35MHz) from a rock-solid DDS VFO with fast (100Hz) and slow (20Hz) tuning steps

*Readout of operating frequency in Morse code, also readout of difference between receive and transmit frequencies in RIT and XIT modes

*Readout of battery voltage in Morse code

*Built-in keyer with two programmable memories (I think this will be increased to 4 memories for the final production version)

*This kit will make extensive use of SMT devices.  Models available for 40, 30, 20 and 15.  Not sure if Jason’s planning an 80m version

* The board will come with the micro-controller installed and pre-loaded with the firmware, though the source code will be freely available for those who want to write and share their own code.

 

If I had a multi-band HF rig, I’d be gunning for a clean sweep with T32C on all HF bands on CW. The one band on which I’d really like to make contact with them on though is 160M. It would be a real challenge from this QTH.

As well as our current beta-testers Mikey WB8ICN, Paul K3PG, and Brian N1FIY, we will be welcoming John AE5X and two more beta testers for the second round of testing before the CC-series becomes available as a kit. Fun times!

September 24, 2011

The CC-20 First Beta Version

Phew.  I’ve finally finished the first CC-20 beta and fitted it into a case.  I can now sit back, look at it and listen to it! In this post a few weeks ago, I showed the unpopulated board with the connectors lying on a sheet of the red PCB material I was planning to use to fabricate an enclosure. By the way, the 6 pin connector you can see at the bottom of the board in the center in the photo in that post is one thing that makes this rig different from many others. It is marked ICSP, which stands for “In-Circuit Serial Programming”.  Etherkit bills itself as an open-source amateur radio company and the hope is that code-minded amateurs will write their own code for this rig if they feel they can add features, or improve on the code that the micro-controller in the kit will come programmed with. If you don’t write code, by the time the kit is available to the general public, the stock code will be solid, so no need to worry if, like me, you’re the type of person who needs others to write your programs for you. I did build a USBtinyISP so that I could flash the firmware on my beta though – the beta kit was shipped to the testers with a version of firmware that is not the final version.

Before we go any further, just in case you’re wondering what the CC-20 is, it’s the first transceiver in what will be known as the CC-series, designed by Jason NT7S.  These are a series of monoband trail-friendly QRP CW transceivers with a DDS VFO, superhet receiver with 3 pole crystal filter, and TX that puts out about 2W.  The kit makes copious use of SMT devices. If you’re good at soldering, have reasonable eyesight and a steady hand, you should be able to assemble this kit, but I wouldn’t recommend attempting it if you have never soldered SMT parts before – it would be best to get your practice on a smaller and easier kit (I built 2 KD1JV Digital Dials, which also uses SMT devices, but is a much simpler project, taking less time to complete).

In that previous post, you saw what the board looked like. Here’s what it looks like when fully populated with connectors and controls wired in. Bear in mind that the final board will be a little (though probably not much) different. This board has some blue wire jumpers that will not be present on the final board:

Of course, the first thing to do after completing the board was hook it up to a paddle, earbuds and antenna, and see if it would work.  The first QSO was with W7VXS in the Salmon Run.  I then rattled off 8 more Salmon Run QSO’s – looks like this little rig works! I also had a regular QSO with K1CTR in Denver, CO.

At some point afterwards (I think it was during an extended key-down period while tuning the TX) the finals overheated and fried. The production version will have a redesigned driver and finals and will most likely have an automatic dotting mode programmed into the firmware to prevent overheating of the BS170 final transistors.  For this version of the rig however, to help guard against this happening again, I epoxied a small chunk of aluminum to the new finals to act as a heat-sink.

Here’s the enclosure I fabricated from PCB material. The great thing about making enclosures this way is that you can make it to whatever size you need.  Finding ready-made enclosures to specific sizes can be a lengthy task that doesn’t always end in success but this way,  I got a case for the CC-20 sized exactly how I wanted it – a nice low-profile enclosure just a little over 1″ high:

The next image is of the CC-20 in it’s enclosure. You can’t see them, but I fitted 4 rubber feet to the bottom of the case. You can see where I accidentally drilled a hole in the side of the chassis, redrilled it in the correct place, and filled in the mistake hole with JB Weld. I did make a number of mistakes on this case from which I will learn if I make any more. I say “if” because making these PCB enclosures is quite time consuming and I’m feeling the strong urge to use ready-made enclosures for future projects:

On the front panel, from left to right, is the headphone jack,  the AF gain control, the CMD button, the FREQ/OK button, and the tuning encoder.  The tuning control tunes in either 100Hz or 20Hz steps, switchable by pressing the tuning knob. The CMD and FREQ/OK buttons are used to access much of the functionality of the rig,  functions which include:

- changing keyer speed

-selecting straight key or paddle

-recording to and playing back the keyer memories

-reading out supply voltage (in Morse code)

-reading out SWR (to be implemented later)

-reading out operating frequency to the nearest 100Hz

-reading out keyer speed

A lot of functionality is controlled from quite a minimal front panel:

What a cracking little radio:

Oh yes. One thing I almost forgot to mention is that after fitting the new finals, I called CQ on 14061 and was replied to by Steve the Goathiker WG0AT. Now that’s a good omen!

Mikey WB8ICN, Paul K3PG and Brian N1FIY are getting close to finishing their CC-20 betas, and I’m looking forward to comparing results. Mikey has already finished the receiver part of his, and our results are similar.  There are a few issues with the first beta that Jason will be working on to fine-tune. This, of course, is the whole purpose of beta-testing.  I was also thrilled to hear that John AE5X will be joining us for the second round of beta testing. I think we will also have one or two more beta testers joining us for the second round, but I’m not sure who they are.

In the meantime, I now have 20M capability and this little radio is fun to operate. Thanks Jason!

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