Dave Richards AA7EE

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 🙂

December 15, 2010

Norcal 2N2/20 Kits Available Again

Filed under: Amateur Radio,Ham Radio,QRP — AA7EE @ 5:46 pm
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The NorCal 2N2 is available again for a limited time!

 

I noticed from a post on the Norcal 2N2 Yahoo Group that there are a limited number of 2N2/20 kits available. I don’t imagine these will last long, so if you’ve been waiting for a chance to build this kit (look here to see how much fun it is) then don’t delay!

February 18, 2010

Baby Steps at AA7EE

No major moves forward at the AA7EE shack recently, just a few little ones.

I’ve been eyeing a fairly tall tree (50-60 feet) that is right at the edge of the apartment building next door.  It’s just a few feet over the property line, and overhangs the small back yard of my apartment building.  With the aid of a slingshot, I attempted to get a line over it some months ago, but this is a built-up urban area and I didn’t try too long or too hard with the slingshot.  It was my first time using one (whatever DID I spend my childhood doing?) and I didn’t want to accidentally put a 1oz lead sinker through a neighbor’s window, or worse, hit a passerby. My initial attempts failed, I stashed the slingshot away and continued to use the Buddistick vertical from my first floor balcony.

The thing about tall trees though is that if you’re a radio amateur, unless you own a tower, they’re near impossible to ignore. Yesterday afternoon I gave in.  I grabbed the slingshot, walked out onto my balcony, took aim, and the next thing I knew the lead sinker had arced over a branch and was hanging just a few feet above the ground on the other side of the tree. Bingo!  It wasn’t as high up as I wanted, but if I had aimed it higher it wouldn’t have made it through the dense foliage to the ground, and a heavier sinker wouldn’t have made it as high in the first place.  It’s a regular catch 22.

Long story short – with the aid of a reel of 26 gauge magnet wire, I now have an approximately 65-70 foot longwire antenna about 35 feet off the ground. The magnet wire will keep my antenna relatively stealthy (I hope). It’s still a pretty crummy location for an antenna, but at least I now have frequency agility with the aid of an LDG Z11 tuner and 4:1 balun.

In other news, I finally fitted a KD1JV Digital Dial to my Norcal 2N2:

This is a really worthy upgrade. The only other thing that this rig could use now is a small electronic keyer. Here’s another view in which you can see the 100 ohm resistor and 100uF electrolytic mounted at the power connector that serve to filter out the low level interference from the display multiplexer:

The 2N2 is an absolute pleasure to listen to.  The only commercial rig I have is an FT-817, and when I use that for the other HF bands, I cringe at the high level of noise generated by the receiver. The receiver noise in the 2N2 is much lower.  There is a clarity to signals heard on the 2N2; in comparison the FT-817 sounds noisy and mushy (it is a great jack of all trades radio though and has served me well).

I also started putting the Fort Tuthill 80 into a case.  A KD1JV Digital Dial should be arriving soon and will be fitted, along with decals (probably yellow, to contrast with the black, as inkjet printers won’t print white).  Here’s a view of the Tut80 without it’s top cover.  Imagine this with a digital frequency readout and yellow decals.  I think it’s going to look pretty sweet:

I’ll save the top view until I’ve tidied up the wiring inside a bit so stay tuned.  John AE5X is waiting on a Ten-Tec TPB-41 case to put his in, and I’m keen to see how he does with it in the ARRL International DX Contest this weekend (if the case arrives in time that is – if it doesn’t, how about a bit of bare board operating eh John?) While we’re talking about cases for the Tut80, Steve KB3SII has designed and is manufacturing a custom drilled and painted aluminum case for it.  Target price is under $35. Check the Tut80 Yahoo Group for more details.

I’ve been trying to get a QSO with the Tut80, but the electrical interference in the evening at this location is so bad on 80 that I can’t hear much without a noise blanker. Oh for a nice quiet radio QTH…….

In the meantime I’m searching for a new living situation. There are two main criteria – affordable rent, and the ability to string a longwire antenna to nearby tall trees. It’s time for me to experience the amateur bands with something more than a marginal antenna. I know that I could probably move away from the San Francisco Bay Area and buy (or rent) a little place on a big piece of land but, for the time being at least, I want to stay in this area. So if you know anyone with a cheap room or studio to rent in the Bay Area that would be amenable to a friendly and quiet QRP operator, send ’em my way!

January 11, 2010

Software Defined or Hardware Defined – Which Way to Go?

The main project going on in the AA7EE  “shack” (for which read “main room of my studio apartment”) has been, and will continue to be, the monumental task of committing my sizable collection of cassettes, CDs, DAT tapes and broadcast carts to backed up hard drives.  This is an ongoing project which I expect to take several years. Over the course of a 22 year career as a DJ, I amassed a lot of stuff that is becoming wieldy and expensive to lug around, so it’s time to start consolidating.

So whenever I’m listening to the radio or soldering something, I’m often also ripping a CD, scanning the artwork, or calling up my friend Antoinette and trying to give her as many of the CD’s that I just ripped as possible. I spent 22 years accumulating stuff (opens in a new browser window) and I now want a good portion of it gone (thanks Antoinette!)

All that aside, the amateur radio goings-on here have included building a neat little direct conversion receiver for 40M – the VRX-1 designed by NT7S and sold by the 4SQRP club. It’s a cool little DC receiver.  I’ve been having a bit of a problem with the input bandpass filter, so it’s on the back burner for a while, but it’s been a fun Manhattan building experience:

NT7S’ fun DC receiver got me all charged up.  The first successful TX/RX I ever built was an 80M DSB TX/RX designed by G4JST and G3WPO and published in the UK magazine “Ham Radio Today” in March 1983. It utilized a direct conversion receiver, to which I added an audio filter built from a 741 op-amp.  It was my first experience with DC receivers, and I remember being surprised that such a simple receiver could sound so good. Jason’s VRX-1 re-introduced me to the pleasures of DC receivers, as well as the technique of Manhattan construction (my first time), so by the time I’d finished construction, I was all primed up and ready to swoon at any direct conversion receiver that might flit it’s tail feathers at me.

John AE5X’s post couldn’t have come at a better time. Allow me to repost this picture of the 80M direct conversion TX/RX that the Arizona ScQRPions will be providing a kit for very soon:

The details are here. I was beyond excited when I found about this (thanks John).

I have a mental list of several different QRP rigs that I want to build, among them the Weber Dual Bander, and either the Elecraft K1 or K2. However……SDR has been on my mind too recently.  I built the SoftRock Lite II for 40M a few months ago and was impressed with the performance for such a simple piece of hardware, and low price too.  Of course, the simplicity of the hardware and the low price is a bit misleading because the signal processing is all done in software.  This is the beauty of SDR though – if a better demodulator or filter is available, you just download it.

I’ve been using the SoftRock to monitor the CW portion of 40M, and then once I see a signal, I can work him on the main rig, which is currently a Norcal 2N2/40.  Yesterday, I built a combined switch and dummy load into an Altoids-type tin so I can easily accomplish switching the antenna between the SoftRock and the 2N2/40.  The 2N2/40 is a cracking little rig – a sensitive low-noise receiver with a stable VFO (after the intial warm-up period).  It has a nice narrow crystal filter too which is great for working people, but not as convenient when you’re trying to find stations to work.

So….what I do is use the SoftRock to look at a wide portion of the band.  With my soundcard, I can look at a 96KHz-wide slice of the band on my screen, and the minute I see a station, flip over to the 2N2/40 and work him. It works well but it got me to thinking – why switch over to a traditional radio to work a station that I find with SDR? Why not just get an SDR transceiver and avoid having to switch over to a hardware defined radio?

Hardly original thinking.  I’m sure it’s the same thought process that has led many an amateur to adopt an SDR rig as their main station radio. FlexRadio are about to introduce their Flex-1500, which is a 5 watt all HF band SDR transceiver.

Mighty tempting and with my limited amateur radio budget, I’m now wondering whether to continue building all the QRP transceiver kits I’ve had my eye on, whether to build the SoftRock v6.3 HF TX/RX, or whether to go for broke and get the Flex-1500 when it comes out.

In the meantime, I have a KD1JV Digital dial on order, which will turn the Norcal 2N2/40 into an even more usable little radio.

Oh, and I have 1,000’s of CD’s to rip and perform hi-res artwork scans.  It’s not as if I’ll be sitting here twiddling my thumbs.

November 20, 2009

The Norcal 2N2/40 CW Transceiver Kit

I’ve been wanting to build a kit for some time now.  I built the Softrock 40 a few months ago as my re-entry into the world of building radio gear. It was my first experience with SMT devices, and it went quite well. However, I really wanted to build a complete transceiver – something I can solder up, stuff into a case, and use to talk to someone on.  It’s been years since I’ve done that.

As a kid I spent countless hours with my nose buried in RadCom, Practical Wireless and various books from the RSGB, staring at the schematics and pictures of all kinds of wonderful homebrew projects.  I built a few too, but spent many more hours just gazing at this stuff.  As an adult, I haven’t changed much, except that we now have the internet, so the opportunities for hours of happy browsing are even more numerous.

I spent a lot of time familiarizing myself with the various QRP CW transceiver kits out there and I don’t think there has ever been a better time to be a kit builder, there are so many good kits available. I looked at the kits from Wilderness Radio – the SST series of rigs (very appealing because of their simplicity),  the Norcal 40A and the Sierra transceiver. Then of course, there is the early 21st century version of Heathkit – Elecraft, and their excellent K1, K2 and KX1 kits. Steve Weber’s PFR3, Weber Dual Bander and MMR-40 from Hendricks kits all received good long looks from me as well. There are some really interesting SDR transceiver kits out there too, but I wanted to build a more traditional little QRP radio this time around.

Phew – so many kits to consider, and the problem for an internet “window shopper” like me is that I often spend so much time reading up about things that I can get to the point where I don’t feel the urge to do them any longer. It has something to do with the art of delayed gratification, which I learnt a little too well as a kid.  The good side of it is that it does save me a lot of money.  The bad side is that I spend a lot of time indoors reading about things instead of doing them.

OK, apologies for the digression. There was one other design that caught my attention, and that was K8IQY’s 2N2 series of transceivers.  The design was K8IQY’s response to Wayne Burdick N6KR’s challenge to design a transceiver that used no more than 22 2N2222 transistors.  No PNP transistors, voltage regulators or IC’s were allowed – the 2N2222 was the only active device to be used.  Dayton 1998 was where the judging was held, and Jim Kortge K8IQY took the prize. For about 10 years, a lot of folk built these neat little transceivers manhattan style until the Norcal QRP Club came along to help those of us who still want to build things, but like to have them in the form of a ready-to-assemble kit. The Norcal 2N2/XX series of kits included a double-sided PCB and to many, this was just too good to resist.

The original run of 500 kits looked like they were close to sold by the time I arrived on the scene.  The club had suspended all online ordering (and as of today, I notice that they have decided to suspend all order processing for a year in order to give their volunteers a good break.)  I lucked out and found an amateur on the Yahoo Norcal 2N2 Group who had a spare unbuilt 2N2/40 kit to sell.  40 meters was my preferred band,  so this was an exciting find for me – thanks Cameron!

While waiting for the kit to arrive, I built an RF probe.  I don’t own an oscilloscope, so the next best thing was an RF probe.  This would allow me to test each stage as I proceeded. The instructions are here. I built mine in an old 1/4″ jack plug.  The body was metal so that the probe would be properly shielded.  The test tip was a piece of stiff wire soldered to the end of the plug, with a piece of heat-shrink tubing placed over the joint:

Then I slid the insulation over the whole shebang, screwed on the body of the plug, added some leads, and voila – an RF test probe for around $2:

The kit was well packed and arrived intact.  Cameron, who had bought it from Norcal months earlier, and hadn’t had time to build it, also included all the replacement parts and updates that Norcal sent out.  A view of the entire kit laid out on my deck:

and a close-up  of the update packets that Norcal sent out (ignore the transparent packet of trimmer capacitors – that was part of the original kit):

From finish to end, it took me about 10 days to build this great little radio. I have no idea how many hours I spent on it.  Some days, I worked for a couple of hours, and then went off to meet a friend for the rest of the day, coming back to put in another couple of hours in the evening.  Other days I worked on it while entertaining company at home, and then there were the marathon sessions where I started in the evening and worked until the wee small hours of the morning when sleep got the better of me.  One time I started work at around 8pm and after many hours of toiling away with the soldering iron, realized that it was 6 o’ clock the next morning! Funny how times just melts away when you’re engrossed in a project.

Here’s a view of the board after I had built and tested the power protection, the receive active power decoupler,  receive main audio amplifier,  receive/transmit keying,  receive mute,  receive audio pre-amp,  receive local oscillator,  receive product detector, receive post IF amp crystal filter, and the receive IF amplifier. That sounds like a lot, but some of the stages were literally just a few components:

Same board, same point during the construction, different view:

While we’re at it, here’s a picture of my workbench/operating position. The candle isn’t evidence of any kind of gothic leaning  – I was using it to help strip the enamel from the ends of toroids after I had wound them:

Speaking of toroids, there are a fair number to wind in this project.  Some folk love winding toroids, more seem to dislike the process.  I take what I think of as a more “zen” approach, which is the same approach I take to all kit building. I take my time when I’m building; I don’t feel any rush to get it done and get the project completed.  Part of the enjoyment for me is in building the kit, so I take my time doing it.  While I’m doing it, whatever needs to be done gets done.  Some things are simple, like stuffing resistors into holes and soldering them, while some things, like winding toroids, take more time. While building, I may be listening to the radio – either some CW on 40 meters or my local college station KALX, which comes from the Berkeley campus.  I take frequent coffee breaks, and may also have company over.  The point is that the most detailed laborious task (such as winding a toroid) can be made more enjoyable by becoming engrossed in the process, or at the very least having something interesting playing in the background! The main point of kit building for me is the journey rather than the destination. Having said that, my toroids, though perfectly serviceable and not all bad looking, are still nowhere near as beautiful as K8IQY’s. He uses a #2 crochet hook to pull the wire through the toroid, and also mounts the core in a small vice while winding.  I hold the small toroid cores in my hand while winding and don’t use any other tools to help the process, so I may think about trying Jim’s technique for my next project.

Here’s the board with the receive chain finished and fully operational. The controls are temporarily wired in for testing purposes. In the center of the board, instead of T6, there is a jumper wire.  This is because on 40 meters the RF receive amp isn’t used:

Wow.  Exciting! There are two crystal filters in this radio – a 4 pole (the main crystal filter) and a 2 pole filter just after the IF amp. The bandwidth of 500Hz sounds just about right.  I have not used a lot of narrow filters in my life, but compared to the 300Hz filter I have installed on my FT-817 (which is a little too narrow for everyday use) this one sounds like a good width for regular CW use.

By the way, in these pictures, the radio is sitting on a schematic of the actual radio being built.  As suggested in the excellent assembly instructions available on the Norcal website, I printed a large version of the circuit diagram to use as a reference while building.  It makes a pretty backdrop for pictures of the 2N2/40 as well.

Here’s the finished board with the temporary wiring for all controls removed, ready for installing in the case:

I’m breezing through the construction in this blog, but a look at Norcal’s assembly instructions will show you that there is a fair amount of work involved in putting together this transceiver. It’s definitely not for beginners, but if you’re good at soldering and have some circuit building experience, it’s not hard. You’ve just got to put in the time. After you’ve built each section, the instructions show you how to make a few measurements to verify that the stage is working as intended.  Don’t skip these tests.  The peace of mind you get from knowing that everything you’ve completed so far is working is well worth the time.

Here’s the board mounted in the case with all the controls attached. Is this thing beautiful or what?

I think it looks decidedly less pretty when fully ensconced in the case, but that’s only because I love looking at components and circuit boards:

A head-on view of the front panel, showing the lettering:

I was keen to see how stable the fully free-running VFO would be.  I haven’t made any measurements but as expected, the VFO does drift quite a bit in the first few minutes after initial switch-on.  If your main experience is with commercial radios controlled by PLL or DDS synthesized VFO’s, you’ll have to get used to the fact that you shouldn’t be switching the radio on and transmitting almost immediately.  I had intended to run some tests to determine the minimum amount of time I should leave the radio on before operating, but since finishing it, I’ve left it switched on nearly all the time.  It uses such little current (measured at around 135ma) that it’s convenient for me to leave it on, so if I wake up in the middle of the night (a regular occurrence) I can listen to the radio and immediately respond to any stations I might hear calling. I will say this – when the radio has settled down to a stable internal temperature, it is easily stable enough for serious CW operating.

The night I finished the radio, I went to sleep, woke up just before 3am, put the earbuds in and worked JM7OLW.  He gave me a 419 with the 4 watts from the 2N2/40.  Not a stellar report, but my first confirmed contact – and it was with Japan!

The sidetone is a little loud for me, so I’ll be adjusting the value of resistor R14 to reduce the monitored transmitted signal to a more comfortable level. The other change I’m going to make will be to add a digital frequency display (probably the KD1JV Digital Frequency Dial.) With these two changes made, the 2N2/40 will be a very serviceable TX/RX for everyday use in the shack.

A few more thoughts on this radio.  If you’ve come from a position of operating mainly commercially built rigs, you’ll probably go through a short period of adjustment when getting used to this radio (or many other similar types of designs.)  As previously mentioned, it has a free-running VFO,  so it needs to be switched on a while before you plan to operate.  It doesn’t have any AGC, so you may need to be a bit more nimble with the AF gain control from time to time to compensate.  The radio does need to be powered by a well regulated power supply, as it has no regulator of it’s own (due to the original design criteria.) Another difference I noticed was the inability to switch to a wider receive bandwidth.  As this is a CW only rig, you may not see the need to be able to set the receive filter something wider than 500Hz. I spend a lot of time at home, and often leave the radio monitoring 7030.  When doing so with my FT-817, I tune to about 7029 and leave the filter in SSB mode.  That way, I can hear anyone calling from about 7029 to a little over 7031KHz. On hearing a call,  I can then zero beat the other station and switch to a narrower filter if necessary before replying. I am not able to do this with the 2N2/40 and feel that I may be missing out on the occasional QSO because of it.

All this being said, it isn’t fair to perform these types of comparisons, as the 2N2 was designed to meet a strict set of criteria for the Dayton 1998 contest, the main one being that the only active device to be used should be the 2N2222, and no more than 22 of them. No “complex” active devices, such as IC’s or voltage regulators could be used either.

Should the above deter you from building this radio? If you specifically want a radio for backpacking and portable operations, there are others that are better suited.  If you’ll be using this at home though, it is a very worthwhile project with plenty of room in the case for you to add your own extras if you wish, such as keyers or frequency displays. I built it because the original design concept caught my imagination, and the changes that Jim has made to the design in the years since haven’t caused it to stray too far from the original idea.

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