Dave Richards AA7EE

August 29, 2011

A Very Early Look At The CC-20 Beta

A few days ago, a small flat-rate Priority Mail box showed up at my doorstep. It was pretty unassuming but it held great promise, as inside was the beta kit for the Etherkit CC-20 transceiver.  Jason has been working on this transceiver kit for quite a while now, and he’s overcome many challenges but finally, his version has a sensitive and stable receiver (superhet with crystal filter) with a DDS VFO that is rock-solid and free of spurs.  You can follow the fun of the beta-build over at the Etherkit forums.

The day after receiving my beta kit, I set about building it with gusto, but didn’t get very far.  Etherkit is billed as “open source amateur radio” so in the spirit of being open, I guess I should ‘fess up and tell you what I did.

Firstly, let me mention that the boards as received are not the final production boards. There will need to be some modifications made to the traces on the board, so Jason modded our boards for us by cutting some traces and soldering in some wiring so that we could use the PCB’s we had at this stage of the game. He also soldered in the DDS and micro-controller IC’s, as well as the 2 regulator IC’s, and checked that they were working before shipping them to us. All I had to do for the very first stage of building was to solder in a diode, an electrolytic capacitor and the power jack, and then check for 3.3V and 5V at the output of the regulators. Simple eh?

You’d think that a diode for reverse voltage protection would be a safeguard against bozos like me, but as well as connecting the power with the wrong polarity, I also soldered the reverse-voltage protection diode in the wrong way.

It just beggars belief. It really does.  Even I am asking myself why I did that.  The moment I connected the power to the board and saw sparks fly out of both voltage regulators I knew it was all over – at least for the time being.

When I build circuits myself from scratch I get things pretty much right because I am checking the circuit as I go. When I build kits, I don’t have to concentrate quite as hard because the instructions tell me what to do.  The problem is that as a beta tester, I should have reminded myself that although this will be a kit in the near future,  right now it is a beta, and I am expected to proceed carefully, checking myself as I go. Somehow, I convinced myself that I had wired things the correct way and didn’t bother to check the circuit board traces in order to make sure, leading to *poof*!

Rest assured that by the time the CC-20 is a finalized product, Jason will have ensured that the only way you could make a simple mistake like this is if for some odd reason, you really want to.

While waiting for extra parts to arrive, I started putting some thought into what to use for an enclosure. I have some 4″ x 6″ sheets of single-sided PCB material, some in blue and some in red, that I think that would look really nifty, so I laid out the board with the connectors in roughly the positions I envisage they will be. Bear in mind that in the final version, the colored side of the board will be facing outwards with the copper-clad side on the inside:

The red PCB material you see is 4″ x 6″, which should allow for a nice easy fit.  I’m thinking that the case need only be about 1″ high. I’d like to take advantage of the fact that the micro-controller outputs the operating frequency in morse code, allowing for a compact installation without a frequency display. Because the majority of the time I’ll be using it at home, I’ll fit an RCA jack on the back panel with an output to drive an outboard digital dial (probably the N3ZI Digital Dial), so when portable, can take a nice compact transceiver with me.

On the front panel, from left to right, is the AF gain control, the headphone jack, the command button, the frequency button (commands the micro-controller to output the operating frequency in morse code),  and the encoder to control the tuning of the DDS VFO. The back panel has the paddle jack, the antenna jack and the DC power jack. There will also be an RCA jack for an output to a digital dial.

I may even start building the enclosure this week while waiting for parts (possibly a new board) to arrive.

This is going to be one really neat little transceiver.

UPDATE:  The replacement voltage regulators arrived from Jason this morning and I was happy to discover that my misadventures with reverse polarity hadn’t fried the DDS and AVR IC’s.  The build continues!

August 23, 2011

OMG

There have been very few times in my life when I have uttered the words “Oh my god”.  I don’t really like that particular exclamation; it’s certainly not my style. For the only the second time I can remember, I just uttered those words twice in a row when this appeared in my inbox just now:

I’m not even going to try and explain how exciting the above is to me.  Don’t worry – I’ll have plenty of words at some point in the future. By the way, although the above mentions the CC-40, I’m pretty sure the beta kit I’ll be receiving will be for the CC-20.

OK, calm yourself Dave. Try to act normal, and suppress the urge to run around in the street and yell gibberish, interspersed with maniacally happy laughter. That kind of behavior is NOT NORMAL.

I also just received notification that my WM-2 QRP Wattmeter kit just shipped today from Oak Hills Research so once again, things will be busy at the AA7EE ranch very soon 🙂

August 14, 2011

Baby Steps Towards Solar Power

Like many, I’ve always found the idea of generating power from the sun an attractive idea. I even went as far as to calculate how many panels and batteries I would need to power my whole apartment from solar – fridge, lighting, the whole lot. Needless to say, it came out a little pricey and I didn’t pursue it any further.  With the current prices of solar panels and batteries, the initial investment in solar doesn’t pay for itself for many years so for most of us, the best reason to try solar is not financial. However, there are 2 good reasons to try it –

1) You don’t have access to cheap electricity from the grid, or

2) You want to do it because you think solar is cool.

Number 2) was my reason for wanting to go solar. I still haven’t been able to justify the cost of a 100w panel, which would quite comfortably power my whole QRP station, plus probably an LED light or two for the occasional power-out, but when I saw 2 very small panels on eBay that looked like they might go cheap, I figured that they’d be a good way to have a bit of cheap fun with the sun.

I won the auction and got 2 x 1.8 watt panels for $12.50 plus 9.95 shipping for a total of around $22. Less than 4W of panels won’t exactly provide a ton of power, but they’ll run my regen, which only consumes around 13mA at 13.8V and a QRPp TX too, as long as I’m not running the TX a lot.

Here’s my super-professional panel installation on the balcony of my house:

About 30 feet of cable leads into my window and into a cheap charge controller I also got from eBay. The charge controller and battery (which is just above the controller in the photo below) are sitting on top of a bunch of stuff on my desk, so you’re looking down on them from above. The iPod in the background runs 24 hours and provides programming for my Part 15 AM operation which I recently started up again on 1600KHz:

Now I have a system that can power my WBR Regen and my 2 transistor Pixie-based transmitter. I’m independent of the grid! When society falls apart, and scared local residents need to get word to the outside world of our predicament, they’ll come flocking to me with my solar-powered regen and 170mW 40M CW transmitter!

Well, maybe not.

When I’m not building slightly more adventurous projects, this is the kind of stuff I fiddle around with on a daily basis.

August 13, 2011

Video Of WBR Regen

I finally got around to putting up a video of the WBR Regen on YouTube. Unfortunately, I didn’t get many good recordings of SSB – this was mainly due to band conditions and the times of day that I was recording. However, it was time for me to get this thing out so that I can move on. First plan is take a break this weekend. I never quite know for sure what my next project will be or when it will begin. This is a hobby and I simply follow my interests:

August 11, 2011

VFO Voltage Regulation For the Norcal 2N2/40

This is not a project by any stretch of the imagination, just a minor mod.  The original plan was to post it to the Yahoo Group for the Norcal 2N2 but Yahoo re-sizes my pictures down and the detail won’t be visible afterwards, so I’m posting here.

Jim K8IQY’s 2N2 series of transceivers are brilliant little rigs. Designed originally for a contest sponsored by Norcal which specified that the design contain no more than 22 x 2N2222 transistors,  the first 2N2 was for 40M, though designs for 30, 20 and 15 followed, to the delight of many Manhattan builders. Then Norcal brought out a kit version of the rig for 40, 30 and 20 and the 2N2 odyssey continued, now in it’s 14th year.

No active devices other than 22 x 2N2222 transistors were allowed in the original design, and although subsequent designs after the contest was over (Jim won first place, by the way) did include different transistors to improve upon the original performance, there was one thing still that I wanted to change. That was the fact that VFO voltage regulation in the transceiver is by zener diode only.  When using the radio with a regulated power supply, this poses no problem, but trying to run the 2N2 from batteries causes the transmitter to chirp.  I have about 44AH of sealed lead acid batteries here in the shack with a charger permanently connected from which I run my other rigs. Anytime there is a power-out, it’s wonderful – all the lights go out, but my little rigs just keep on truckin’! I love the idea that the grid could fail, but I’d be able do a little CW on 40M for at least a few days 🙂

In the Yahoo Group for the Norcal 2N2, Bob WB2SRF told us how he used an LM431 voltage regulator, along with a couple of resistors and a tantalum capacitor as a direct replacement for D9, the zener diode that regulates the tuning voltage to the main VFO varactor.  I was in. The messages describing the mod are here and here. You’ll need to join the group to view them.  The schematic for the mod is in the photos section of the group under the title “Norcal Voltage Reference”.

The capacitor was mounted underneath the board. It’s only a 16V cap. I’d have preferred a larger working voltage, but there is limited space under the board (Edit: Bob reminded me that a 16V cap is perfectly OK, as it is across the output of the regulator – don’t know why I didn’t think of that!) The leads from the cap are soldered to the holes that used to anchor D9 and protrude through to the other side by about a centimeter so that the rest of the assembly consisting of the LM431 IC and the 2 resistors can be soldered to them:

I used 1/8 watt resistors for the above-the-board part of the assembly, to save space. Here it is with one of the resistors attached to the LM431 device. When soldering things, I use any tactic I can think of to make the wires stay exactly where I want them until the solder has cooled. In this case, I stuck the small assembly into a packing peanut and weighted it down with a pair of long-nose pliers, so that it would stay in place while I was soldering it together.  Note that in this picture the 1K 1/8 watt resistor has been soldered into place, but not the 1.5K resistor:

One thing to note if you’re a Norcal 2N2 owner and are thinking of performing this mod, is that on Bob’s schematic in the pictures section of the Yahoo Group, the pin-out numbers for the LM431 may not correspond to the device you have; they didn’t for mine.  I just made sure I knew which lead was the anode, cathode and reference, and figured out the wiring from that. Here’s the final assembly installed in place of D9 on the board. These boards get a bit busy, so I’ve circled it in red:

The mod works well. I can now power my 2N2/40 from a 12V battery with no chirp on transmit at all. I did have to re-adjust the drive to the final as it was putting out less power on the batteries than when powered from the PSU. I re-adjusted for the QRP gallon (5 watts) and all is well.

There is only one more very small thing I’d now like to change for my 2N2/40 to be the perfect one band CW rig, and that is to install a switch for the RIT and replace the center-detent pot with a pot that has no center-detent. If I need to apply a small amount of RIT the pot won’t let me, as it keeps wanting to click back into the center-detent position. Being a little picky, this gets my goat, as I like to hear the station I’m listening to at exactly 500Hz. This one mod, if I get around to it, will turn a very-close-to-perfect QRP rig into an absolutely perfect QRP CW rig – from my point of view at least 🙂

August 9, 2011

A 2 Transistor Transmitter Powered From a 9V Battery

A couple of days ago I built a simple 2 transistor transmitter on a small piece of PCB material. I used the style of construction that seems to be becoming my default – Manhattan-style using MeSQUARES from QRPMe. Rex is out of stock as I write this, but expects to have them back in soon. It’s definitely easier stuffing a ready-made PCB with parts and soldering them, but you don’t get as much of a feel for the circuit as you do by by building this way. With Manhattan construction, you can look at your build at any time and easily visualize the schematic. It’s a lot harder to do that with a circuit built on a PCB.

This is a simple project – it’s a version of the Pixie 2 as implemented by W1FB. I didn’t want the receiver part of this transceiver – just the transmitter, so it simplified construction even more.  I won’t go into any lengthy descriptions this time. You can relax – it was a pretty straightforward build. Here’s what it looked like when finished. See the resistor with the red lead attached to the top? Just behind it is a micro-switch that can be used to key the transmitter, though I prefer to plug in my AA0ZZ keyer from 4SQRP:

The slide switch is a DPDT.  One pole switches the antenna between the TX and the outboard RX.  The other pole disconnects the 9V supply on receive so that you are not listening to the crystal oscillator (which runs continuously) when trying to hear the station you are working. I teamed it up with my pride and joy, the WBR Regen Receiver and the first QSO was with Greg AK7Y in Alpine, AZ – a distance of 781 miles. He gave me a 449 – not bad for a transmitter that was only putting out about 170mW – that’s 0.17 watts! I  must admit that listening with the relatively wide bandwidth of the WBR was a test for my operating skills, and I might try using my Softrock Lite II receiver next time with the filter set to narrow. Nevertheless, it felt good to be using such a simple transmitter-receiver combination. Even better – this first QSO qualifies me for the 1,000 miles per watt award!

For a long time now, I’ve wanted to be able to send out a QSL with a hand-drawn schematic of the transmitter I was using on the back, and this was my chance. Here’s the back and front of the QSL I’ll be mailing to Greg on Tuesday:

Reader Erwin pointed out in the comments below that the oscillator stage is missing an emitter resistor. Unfortunately, the QSL was sent out a long time ago, and it is too late to correct that but for anyone wanting to build this circuit, please note that there should be a resistor of about 1.5K value in the emitter lead of the first transistor. Thank you for pointing that out Erwin!

Of all the QSL’s I’ve ever sent, this one feels most in the true ham radio spirit.  I’d like to think my radio ancestors would be proud, though if they were alive today they’d probably be running Flex radios 🙂

August 2, 2011

The Messiness of Home-Brewing and The Echolink QRP Conference

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The previous post felt like a triumphant one. I built N1BYT’s WBR Regen, housed it in an enclosure I also made myself and it worked very well. It was one of those home-brew projects that turn out exactly the way you’d hoped it would.  The number of positive comments received was quite overwhelming and to be honest, I think the receiver looked a little better in the photos than it does in real life. I can promise you that I didn’t use Photoshop though – those pictures were almost straight out of the camera – just a little adjusting of levels and a tiny amount of sharpening applied. I even received positive feedback from Rich Arland K7SZ and Daniel N1BYT himself.  It was very encouraging, and I was so impressed by the performance of this simple receiver that I began work on another one, intended for general coverage. I did the calculations, wound 42 turns of wire on a T68-6 and figured I should be able to get something in the region of 3.5 – 12.5MHZ coverage when tuned by a pair of MVAM108 varactors.

Building started off well:

I then finished off the regenerative detector and before building the audio amp stages, fed the audio into an outboard amp, whereupon the trouble started. I’m pretty sure that I’m getting regeneration, because I can hear the onset of hissing as I adjust the regen pot.  Also, when I touch the coil, the hissing stops, indicating that the frequency of oscillation is changing, thus altering the point of onset of regeneration – or even ceasing oscillation altogether, so I’m pretty sure that means it is oscillating.

But I’m not receiving any signals and I’m not sure why. I haven’t been successful in connecting a frequency counter to the receiver.  I did hear of someone who was able to couple a WBR regen to a frequency counter by way of a coil placed near the WBR’s coil, but this hasn’t worked for me. Attempting to connect the counter more directly just stops the oscillation.  I’m wondering if the varactors are working, and if I could measure the oscillation frequency of the regenerative detector I might be able to ascertain this.

To be honest,  I’m a bit burnt out.  I think I’m going to carefully place this second WBR regen in a box somewhere and maybe come back to it some other time. Home-brewing can really frazzle you and take over your life if you let it. Just ask Jason NT7S.  Jason has been diligently working on the CC-40 and CC-20 transceiver for a while now. He’s had a number of setbacks, none of which have gotten the better of him, though they have cost him much time and I’m sure a great deal of stress. If you follow him on Twitter, you’ll have some idea of what he’s been going through.  My setback with the second version of this regen pales in comparison to what Jason has been experiencing. He designs circuits from scratch, while I merely copy other people’s. There is a world of difference. I’ll bet that anyone who designs their own circuits can understand what Edwin Armstrong went through.  Building your own stuff is a messy business, so I can’t begin to imagine how much messier designing your own stuff is.

In other news, I joined the Echolink QRP Conference on Sunday. This is a weekly net for QRP’ers that meets on Echolink node 140904 every Sunday at 9pm EST. They’re a friendly bunch of folks, and I had the fun of realizing that one of the participants in the net, John NG0R,  is on my blogroll. The QRP community is a small world. If you’re a QRP’er, you might want to try joining them.  If you don’t want to talk, you can always type “.lurk” in the chatbox and you don’t have to participate – you can just listen.

So that’s it.  I’m feeling a bit beaten down by my unsuccessful project. I am missing having general coverage in the shack and am wondering what to do about that.

 

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