Dave Richards AA7EE

June 24, 2014

Building A WBR Regen Receiver For The 31M Broadcast Band (or the 30M Ham Band)

Note – some of the narrative in this blog-post assumes that you have access to, and have read, N1BYT’s original article on the WBR Receiver in the August 2001 edition of QST.

EDIT – as of July 2016, I just modded this receiver to cover the 30M ham band only, and have been surprised by it’s sensitivity. My WBR’s appear to be more sensitive on SSB/CW than AM.

It has been almost 3 years since I first built N1BYT’s WBR – a regenerative receiver for the 40M amateur band. It was an intriguing design for me, as it employed a Wheatstone Bridge arrangement to minimize oscillator radiation into the antenna without the use of an RF amplifier stage. Unlike older tube designs, more modern semiconductor regens don’t generate as much RF energy, though although you might think that the need for minimizing radiation into the antenna is less, that is not the case. Radiation into the antenna can be the cause of one malady that plagues some regens – that of common mode hum. This circuit avoids that. It is quite a unique design. In fact, unless I’ve missed something, you have to go back to the 1920’s in order to find anyone who was designing along the same lines, as Mike Rainey AA1TJ relates in this post of his.

Such was my pleasure at the performance of this little receiver, I have often wondered how it would adapt to other frequencies. I did briefly try to make a general coverage version of it but for some reason, couldn’t get the oscillator stage to oscillate and gave up on it far too soon. Then, a few weeks ago, I started wondering about building a second WBR, for the 31M shortwave broadcast band. I already had a small aluminum enclosure into which I knew I wanted to put the finished receiver, and some months earlier, had cut a piece of PCB for whatever Manhattan project would find it’s way into the box, so getting the envelope of MePADS and MeSQUARES out and beginning to build didn’t take much of a leap, once I had found the initial inspiration.

A few rough calculations revealed the number of turns that would be required on the toroid for this new, higher frequency coverage, and they proved to be correct. I guesstimated that I should be able to achieve something of the order of 500KHz of coverage, which would allow the receiver to tune the 9400-9900KHz 31M band. I was also hoping to be able to cover up to 10MHz in order to be able to receive WWV and as it turned out, that was indeed possible. As well as a new frequency range, I decided to try a different configuration for the LM386 AF amp. N1BYT uses the 386 in it’s standard high-gain configuration that places a 10uF capacitor between pins 1 and 8 of the chip.  This has the advantage of providing high gain with low component count (an important consideration if you are to engage as many builders as possible), but it is also an approach that results in a lot of hiss. If you’re using a regen, you’re already dealing with a fairly high amount of hiss, so I wanted to at least remove some of that from the audio stages. In his Micro 40 DSB transceiver, Peter VK3YE uses the LM386 in a way that still gives high gain, but is a bit less hissy. Much has been written in the pages of SPRAT on trying to eke more gain from this venerable and much-maligned little chip, and Peter’s circuit appears to be based on LA3ZA’s ideas in SPRAT 116 (page 4). This circuit worked well in the Micro 40 I built, so I decided to use it in this, my second build of the WBR. I also incorporated a pre-amp stage, as suggested by N1BYT in his original article in the Aug 2001 issue of QST.

On completing the receiver, I noticed that it seemed a little deaf. The WBR was a project in the QRP-Tech Yahoo Group (Yahoo membership required), led by Chuck K7QO, and a few builders there also experienced lack of sensitivity. I am wondering if they made the same mistake that I made with both my builds of the WBR – to miss the fact that the full details of Z1 were not published in the original QST article. A later list of corrections revealed that Z1 was intended to be a metal strip measuring 1/8″ x 1/2″ and connected to ground via a short wire. In both of my WBR builds, I used a piece of stiff wire instead of the recommended metal strip, as detailed in the original article, and was perhaps inadvertently placing too little inductance at Z1.  Although Dan N1BYT does warn against increasing this impedance, lest it lead to detector overload, LA3ZA found that an inductor of 0.22uH at this point helped the sensitivity (and presumably didn’t overload the detector). Builders in the QRP-Tech Yahoo group experimented and found values between 0.22uH and 1uH to be optimum. I followed a slightly different route, first adding a 0.3uH inductor, consisting of 9 turns wound on a T37-6 toroid core. This increased the sensitivity dramatically, but also resulted in breakthrough from a local religious broadcaster on 1640AM. Instead of experimenting with lower values of inductance, for some reason, I added a simple BC band trap. At first it appeared to solve the problem, but then I noticed that although the AM breakthrough was much diminished, it was not, in fact, completely gone. At this point, I reduced the number of turns on my T37-6 from 9 to 4 and found that it did the trick. My WBR was still quite sensitive, yet without the disadvantage of breakthrough from strong broadcast signals. I left my BC band trap in circuit but would suggest if you build this circuit, you first experiment with the value of the inductor before deciding whether to add the trap.  Keep the value of inductance as low as possible and depending on where you live, a trap may well not be necessary. EDIT – Jason NT7S has also built a WBR using the schematic published here. He reduced the number of turns on his inductor to just 3 and found no need for a BCB trap, despite having a strong local station at 1390KHz that was causing detector overload when the number of turns on his inductor was 4. It pays to experiment! See the bottom of this post for more info on Jason’s experience with the BCB trap and for a video of his WBR in action. Jason also found that the BCB trap I detailed here does not have an ideal response. Details of that are at the bottom of this post.

I know there are some experimenters who are sitting on the sidelines waiting to build a WBR, but who are a little confused by the various mods published, and want to see more information on a successful build before going ahead with their own. By sharing detailed information on mine, I’m hoping a few more people will be encouraged to build their own version and share their experiences – the internet is a great way to do this. Many thanks to Dan N1BYT for graciously giving me the go ahead to show you a full schematic for this version that I built. The only changes I made to the core part of the circuit (the regen stage and the infinite impedance detector) were to employ a 10-turn pot for the regeneration (with a 33uF cap across it to stop the “whizzing” sound), the addition of the trap, and the substitution of Z1 for a small toroidal inductor, a mod that was first publicized by LA3ZA. The actual value of this inductor may require experimentation on the part of the individual builder but, and this does bear repeating,  it is wise to err on the side of keeping it small in order to avoid detector overload. My 40M WBR uses just a piece of stiff wire for Z1, and I have never heard any kind of breakthrough from all the signals my outside antenna deliver to that defenseless little receiver!

If you are thinking of using the optional AM BC band filter, I have since discovered that the attenuation of this filter is not as high as I had hoped. Give this one a try instead. It uses molded chokes instead of toroids, which some builders may prefer.

 

The description of circuit operation is contained in the original article which is readily available to ARRL members. Having read horror stories of unstable and unpredictable regen behavior by some builders (not of the WBR, I hasten to add), I was pleasantly surprised to find that the WBR has smooth regeneration control with no hysteresis, and is overall a tame set to operate. I have read that for solid state circuits, the designs that incorporate a separate Q-multiplier and detector (as does the WBR) tend to work better. Whether this is fact or hearsay, I am not sure. I have found it quite difficult to separate technical fact from folklore in the area of regens. This could be partially due to the fact that many builders, like myself, don’t have an in-depth knowledge of the workings of these circuits. Add that to the fact that regens are particularly dependent on good RF practices and solid physical construction, and I suspect that some designs are declared to be wanting simply because the experimenter didn’t build it properly. Likewise, due to lack of knowledge on the part of many builders, marginal regen designs are published and propagated by people who don’t have the ability to discern whether a circuit is “any good” or not. The world of regens seems to be a mystical and magical one inhabited by equal parts myth and fact.

I used 10-turn wirewound pots for both the regeneration and tuning controls (Bournes 3590S-2-103L). These pots aren’t cheap and if you need to save money, you can use a preset to set the approximate regeneration voltage range, and a regular 1-turn pot for the regen control, as N1BYT describes in the original article. A 10-turn pot does seem to give more precise control over the regeneration though. If you use a wirewound pot here, add a 33uF capacitor between the slider and ground, as shown in the schematic. This will eliminate the “whizzing” sound as you rotate the pot. I have an affinity for 10-turn pots, so I used them for both controls. I like the fact that I don’t have to bother setting the approximate regeneration range with a preset, as I have the full range of control voltages available to me immediately with the 10-turn control. The 10-turn seems to give better control over setting the receiver for the threshold of oscillation. Also, when using the injection of carrier to receive weak AM stations, the regen control can be used as a very fine tuning control in order to set the receiver to zero beat when in exalted carrier reception mode. Adjusting the regen control does have the effect of slightly shifting the frequency of the receiver, which can come in quite useful when wanting to make critical adjustments to the tuning of the receiver. Incidentally, this is a good reason to pay close attention to the physical construction of your WBR. You won’t be able to set the receiver for exalted carrier reception if it’s not stable enough.

The one disadvantage of using a 10-turn pot for the tuning is that you can’t see at a glance roughly where you are in the band. An arrangement of two 1-turn pots, one for bandsetting, and one for bandspread, will be cheaper, and will allow the operate to easily judge where he is in the band simply by looking at the setting of the main bandsetting pot.  Other arrangements might be possible. One thought that comes to mind is the use of an old-fashioned vernier reduction drive with a logging scale connected to a 1-turn pot. This would allow for quite accurate calibration of the dial and of course, the ability to see where you are in the band with one glance. The expense and trouble may not be justified, but if you already have one on hand, it would be an intriguing option. Expanding on this – how about a version of the WBR with plug-in coils for wider coverage? The padder and trimmer capacitors could be included in the coil form so that each frequency range could be adjusted individually. Well – that may be too fanciful an idea, but imagination is free! If you’re using a 10-turn pot, how about one of those turns counter dials combined with your own personalized logging chart? This is an idea I may try to implement in my build of this receiver at some point.

When setting the frequency coverage, you can run a short piece of wire from the antenna lead of a general coverage receiver close to the main tuning coil of the WBR and turn the regen control in order to make the set oscillate. Then, listening to the WBR oscillator in your receiver and with the tuning pot in the WBR turned fully clockwise, set the trimcap for the uppermost end of the desired frequency coverage. Twist the WBR tuning pot fully counter-clockwise, and use the 5K trimpot to set the bottom of the tuning range. With the values given, I was able to get my WBR to receive as high as 10.3MHz and lower than 8.6MHz, giving me the ability to pick any 500-600KHz tuning range within those limits. It would be a fairly simple matter to set the WBR to receive on any desired band of frequencies by changing the number of turns on the coil and/or the value of the 47pF padding capacitor (the capacitor in parallel with the trimcap).

Here’s the basic board. At this point, the only inductance between the center-tap of the main tuning coil (the big one on the yellow T68-6 toroid) and ground is a short piece of stiff wire.  Also, the AM BC band trap hasn’t been built yet (I didn’t know that I would need it). The cables for the various connectors have been bundled together in order to look neat for the picture –

On connecting this board up, the receiver seemed a little deaf, To be fair, although the original article doesn’t mention it, corrections to the article published in a future edition of QST did mention that Z1, the impedance between the center-tap of the coil and ground, should have been drawn as a metal strip 1/8″ wide, 1’2″ long, and grounded to the board with a standard piece of wire. I was using just a piece of wire, as you can see in the photo. This probably wasn’t providing enough inductance. I clipped part of the wire connecting the center-tap to the ground plane, and inserted an inductor consisting of 9 turns of wire on a T37-6 toroid.  This is an inductance of about 0.3uH. Wow – what an improvement in sensitivity! Unfortunately, a local broadcaster whose transmitter on 1640KHz is just a few miles down the road from me, was breaking through. This was presumably caused by detector overload as a result of increasing the impedance at Z1. I added a simple AM broadcast band trap which I initially thought had solved the problem, but later discovered that the breakthrough was still there, albeit at a much lower level. I rewound the T37-6 toroid with 4 turns, for an inductance of about 0.05uH. Bingo! Breakthrough gone! In retrospect, a better way to proceed would have been to attempt to find an optimum value for the inductor that would have given good sensitivity while still avoiding overload of the detector, before adding the trap. Here’s the board after the trap was added, and the center-tap of the coil modified. The stiff wire to ground was cut and a 10M stand-off resistor inserted in it’s place to help with rigidity, before adding the inductor wound on the T37-6 toroid. This is the first version of the inductor, with 9 turns. The later version had just 4 turns –

Time to box it up. I’ve had a couple of small aluminum cases from LMB Heeger that I bought because I thought they’d make great cases for small projects.  It’s their model #143 in plain aluminum finish, though it is also available in grey and black. One thing I particularly like about it is the small lugs on the top cover – 2 at the front and 2 at the back – that prevent the front and back panels from flexing inwards. This feature helps to make it a very stout little case. This enclosure was the obvious choice to make a nice compact receiver out of this version of the WBR –

 

After a few hours of listening to it (what fun!) the AF amp began to make occasional motorboating-type noises. It appeared that audio peaks were changing the regeneration point and pushing the set into slight oscillation. The battery was still at about 8.5V, so this should not have been happening. While researching possible causes, it occurred to me that in reality, this receiver was going to spend nearly all of it’s time in my shack, meaning that I could run it off the shack gel cell power supply. Instead of solving the issue I took the easy way out, removing the battery holder and fitting a jack for a DC power supply, along with a series diode for polarity protection. The receiver can easily handle the ~0.6V voltage drop from a 12V supply, and if you use the reverse diode to ground method with a bigger 12V supply, it will blow the diode like a fuse if you inadvertently connect the power to the set the wrong way round.  With a small 9V battery, it’s internal resistance should prevent it from passing enough current to blow the reverse diode. Also, you cannot afford to drop 0.6V from a 9V supply, hence the reason for using the method pictured in the schematic. The holes that were previously used to mount the battery clips became tie points for the antenna cable –

My downstairs neighbor’s cat was standing over the WBR in this next shot. You can see his whiskers in the top right-hand side of the frame. I think he’s interested in regens. In these next 2 shots, you can also see the lugs on the top cover that help to make this such a stout little case. It’s a neat little receiver –

From time to time, I am asked what knobs I use for my projects. They are manufactured by Eagle Plastics. I get them from Mouser, though I’m sure they’re available through many other outlets.

The large one I use for tuning is part # 450-2039-GRX (the exact same knob is also available from Radio Shack, and is RS catalog # 274-402

The medium sized ones I normally use for AF gain, RF gain etc are part # 450-2035-GRX

and the small ones I use for AF gain, RF attenuation, and regeneration in this receiver (because space was at a premium) are part # 450-234-GRX

For wiring up the connectors, I use a thin cable consisting of 2 conductors plus a shield. It’s made for lavalier mics, so is skinny and flexible – ideal for wiring up pots and jacks. I used to get mine from a local pro-audio store that recently closed down, so had to find a new supplier. Most places online seem to either want to sell large reels of the stuff or, if they do sell it by the foot, charge too much. I found a place in Connecticut called Redco that sell it by the foot for a reasonable price. On top of that, they will ship via first class USPS mail, which helps to keep the cost down. I haven’t tried any of this new batch yet, but it’s a quality cable made by Mogami (type W2697), and it looks like it will do the trick.

RF connections (like from the antenna connector to the RF attenuation pot) are made with Belden 8215 RG-174/U.  It’s skinny and flexible.

Following are a number of videos designed to show different aspects of this regen, My old camera takes awful quality video (sorry about that) and limits the clips to 3 minutes, which is why there are several videos instead of one long one.

This one shows how the set has quite a narrow bandwidth when set to the point just below oscillation. In all these videos, the WBR is directly driving an external speaker. There is no external amplifier connected –

In this video, you can hear how the audio bandwidth broadens out considerably when the set is oscillating –

Tuning around the 31M band. There aren’t many strong signals, as band conditions generally have been poor. It’s not due to any shortcomings in the WBR –

This video shows how stable a homebuilt regen can be. I could have made mine more impervious to knocks by holding the toroid with a nylon screw and washers, but that might have introduced more long-term drift –

Another video just tuning around. It cuts off rather suddenly at the end –

This one shows how effective the technique of exalted carrier reception can be – and you can do it with a regen! –

It seems fairly sensitive, and quite stable, both in terms of it’s response to physical knocks, and the long term drift. I like regens over direct conversion receivers, because of their ability to demodulate AM as well as CW and SSB transmissions. I suppose that with a very stable VFO (a synthesized one perhaps) a DC receiver could receive AM in exalted carrier mode but with a regen you can actually take it out of oscillation and receive AM with no carrier injection. The regenerative detector is a versatile one.

The only criticism I have of this particular build of the receiver is that I seem to have a noisy LM386. The 386 stage is generating a type of low frequency random scratchy noise that wasn’t present the last time I used this circuit configuration (in the Micro 40). I have heard that there is enough variation in these chips such that you can get a particularly noisy one. This chip was part of a batch of cheap ones I bought from eBay. I just ordered some LM386N-4’s from W8DIZ. They seem to be quality parts from National Semiconductor and because they are LM386N-4’s, they have higher power dissipation and a higher max supply voltage (16V) than the others (12V), which can’t be a bad thing. I may, at some point, put one of Diz’s 386’s in place of my eBay cheapy-chip in this set.   EDIT June 25th 2014 – I just replaced the eBay cheapy LM386 with an LM386N-4 from W8DIZ and the scratchy rumble is gone! The ones that Diz sells are National Semiconductor devices and of course, they still hiss, because they are 386’s being used in a high-gain configuration. With a good 386 though, the noise is just a smooth hiss that is much easier to deal with than the scratchy rumble of the bad part.  Here’s what the sub-par IC sounded like. The hiss is normal for a LM386 used in a high-gain configuration, but that scratchy rumble is most definitely not –

Jason NT7S built a WBR using the schematic in this post. Instead of building it for the 31M band, he built his for the 40 amateur and 41M broadcast bands. If I remember correctly, he set his coverage for 6900 – 7500KHz, which gives him coverage of the pirate BC band at around 6925KHz ±, 40M from 7000-7300, and 41M from 7200 – 7450KHz, though it does make tuning SSB and CW a bit tricky. If you want to make tuning SSB/CW easier, then you can limit the coverage of a 40M RX to just the amateur band. If you’re a hpone-only person, you could have your WBR tune 7150-7300 (in the US) for much smoother tuning! Before removing a turn from his antenna-input inductor, Jason was getting breakthrough from a strong local station on 1390KHz – even with the AM BCB trapin place. He did a sweep of the trap on his scope and here was the result.  The marker is at 1390KHz – the strong undesired signal –

Note how the attenuation of the trap is only about 5dB at the frequency of the unwanted signal. I may take another look at the values of the components in this trap with a view to increasing the cut-off frequency but my first step will be to also remove a turn from my antenna-input inductor to reduce it to just 3 turns and see if I can also manage without the trap.  Thank you for this input Jason!  Jason’s WBR sounds great. It is the first time he has successfully built a regen, and I’m tickled pink that I was able to inspire him to build this one. I don’t think he was disappointed either –

Jason sent me this picture of his WBR, all wrapped up in a smart blue enclosure.  Aluminum for the bottom half, and PCB material for the top half, if I’m not mistaken. I like the attractive pattern of holes for the speaker cut-out. Is the bottom half from an LMB Heeger Crown Royal enclosure, by any chance? Nice! –

Jason NT7S’ WBR in it’s attractive blue enclosure. Jason built his for coverage of 6900KHz – 7500KHz.

This successful build of another WBR is helping to pull me down the rabbit hole of wanting to build the perfect regen. My goal is to build a really good general coverage regen on a nice-sized chassis with plug-in coils for band changes. I am starting to collect parts with this goal in mind and being relatively inexperienced with regens, have many questions in my mind, such as

– semiconductors or tubes?

– separate detector and regen stage, or an oscillating detector?

– an FET or a bipolar detector?

– high mu, or low to medium mu tubes for the detector?

– throttle capacitor with ball drive, or resistive regeneration control?

– toroids or traditional coils?

– any other considerations?

Although I’m secretly looking for a solid technical reason to make my dream general coverage regen a tube design, a semiconductor one would probably be best, as long as I’m not potentially giving up anything in performance. If any experienced regen builders are reading this and have any ideas, I’d love to hear them.

Oh – and the downstairs neighbor’s cat, whose whiskers you saw poking down from the top of the frame in the shot of the WBR from the back? That’s Stephen. He likes regens (I think). Here he is wondering what magical electromagnetic signals there are out there in the ether. He might also be looking at a bug –

Such an enjoyable little receiver. Thank you for the circuit once again N1BYT.

August 26, 2009

On QSL Cards

Filed under: Amateur Radio,Ham Radio — AA7EE @ 6:50 am
Tags: , , , , , ,

I knew when I became active on the air again a couple of months ago that I would have to deal with the question of QSL cards sooner or later.  I’m currently unemployed and am watching all my expenses closely. Even so, it seems against the spirit of amateur radio not to reply to QSL requests – even if I were to make it perfectly clear on my QRZ page. So that option was out of the window. At the time of writing this post, I’ve made the statement on my QRZ page that an SASE will be much appreciated for anyone that wants a QSL. I’m going to start using LOTW and will probably renew my relationship with eqsl, as well as figuring out which bureaus to use. That still left me wondering what to do about an actual physical QSL card.

When I started in the UK as G4IFA (actually, my first call was G8RYQ,  but it was short-lived, as I upgraded to the full G4 license within a few months) my brother drew a great cartoon of a ham sweating away at the key.  I wish I still had a copy of that card. Next came a home made affair constructed with lots of cutting and pasting (the old-fashioned way – not on the computer) and photocopiers:

By this time I figured it was time to try a professionally printed product.  These 2 cards were from Rusprint:

The Rusprint cards were great, but by now my address had changed twice and besides, I am into CW for the first time, and I wanted a card that reflected that. One thing that I learnt from the Rusprint experience was that my requirements of a QSL card tend to change a long time before the cards have run out, leaving me with a stack of fairly useless cards. I liked the idea of a simple yet informative and elegant card that would be easy for me to design and print at home, so that when my circumstances change (like I move, or start operating 80m AM and want to change my card yet again), I can make the changes, and only have to print what I need as I go along.

Then I found out that Kinkos, or as they are now called “Fedex Office” will let you upload a file online and go pick up your order a couple of hours later (sometime sooner) at any store you choose. Brilliant – I don’t have to fuss with printer cartridges, and all those pesky cleaning cycles that use up a lot of ink. I realized that I could fit 4 postcard sized QSL’s on a single piece of 8.5 x 11 stock and cut them myself at home with a box cutter and metal rule. The prices are quite competitive with the professional QSL printers. In some cases, it costs a bit more to do it yourself (especially if you’re printing color, and not just black and white) but to me, the ability to just print the quantity that I need, and make changes as necessary give the homebrew method the advantage.

I had decided that I wanted a card that was fairly functional and simple, yet appealing in it’s design. Operating CW has made me feel quite connected to the roots of this hobby, so I started looking at designs of QSL cards from the 20’s and 30’s. I liked the idea that cards of that era were simple and functional. They served to confirm a radio contact, and they did it perfectly. Some of the full color photo cards we have today feel like overkill in some ways to me, and besides, they cost too much to print! On top of that, I just think that a lot of old QSL cards look great. Steve VE7SL had cards printed by VE7DK that closely resembled many vintage cards, and I was impressed with the result. This page shows some vintage cards from Steve’s collection (opens in a new browser window) and also the card that he had VE7DK print for him. As an aside, Steve built his own replica of a “Paraset” (opens in a new browser window) – a British WWII spy transceiver. If you work him on his Paraset, he’ll send you one of his lovely vintage cards.

A few hours on the computer, and I had found a free old style font and put together a card with the help of Photoshop. I used much of the wording on VE7SL’s card, but did change it a little to suit my needs. He has spaces in which he can enter the voltage and current to the final transmitting tube, as was customary back then. I changed that to a simple space for power in watts, as I don’t have plans to build a tube transmitter. I also added my SKCC and NAQCC numbers, and made one or two other changes. It might seem like plagiarism, but this design was very basic and common for the era. I particularly like the idea of having the station callsign in large letters “behind” the QSL info.

Here’s my new QSL card:

It’s one sided, so it’s cheap to print – even cheaper if I want to print it in black and white on a colored card stock, and I can stamp and address the other side to take advantage of cheaper postcard rates. Some hams don’t like to send their QSL’s like postcards, because of the opportunity for damage in transit, but here’s another way to look at it; those old QSL’s with stamps and hand-written addresses on now are even more appealing 70 years later. The stamps that might seem pedestrian to you now, serve as a historical timestamp to folk who might be viewing them in the future.

Set up a sked with me so I can send you my new QSL card!

July 9, 2009

The Awesomeness That Is The Signalink USB Sound Card Interface

Filed under: Amateur Radio,Ham Radio — AA7EE @ 6:34 pm
Tags: , , , , ,

Anyone that has been following my Twitter will already know that I’ve just become active on WSPR.  As of now, there are just 3 people following my Twitter – my brother Simon, who as far as I know, isn’t interested in amateur radio at all (and probably didn’t realize that my Twitter is strictly amateur radio related when he signed on to follow me, so is probably wondering why I’m such a geek who speaks only in jargonese),  some company called “Memory Suppliers” (why are they following me?), and my friend Antoinette.  Antoinette is my biggest hope here, as she actually bought the Radio Amateur’s License Manual at HRO a few weeks ago and has declared an interest in getting a license, so I’ll keep my fingers crossed that she pursues it.

A couple of weeks ago, I found a blog by Jason, NT7S.  Jason is a Buddipole employee and an electronics and radio nut with a strong passion for electronics and radio.  (What is it about these politically correct phrases that look as if they just popped out of a boring resume?  I’d much rather be described as a radio nut than as someone with a “strong passion for radio.”  It’s the anti-corporate side of me coming out.  I don’t know Jason personally, but I think he’d understand.)  One of his blog entries discussed a mode that was new to me – WSPR,  and my interest was piqued.  Check out Jason’s blog when you have time.  It is written from the perspective of someone who has a strong technical background, but he has a personable manner that makes you feel as if you’re on the same journey as him.

Back to WSPR. If you’re a radio amateur (and I’m hoping that before long I can persuade a few hams to sign up for this blog),  and you have any kind of interest in the propagation of radio waves, WSPR may well be of interest to you.  Have you ever worked on an antenna and wondered how it’s getting out, but felt that you’ve asked your ham friends for signal reports one too many times? Perhaps you just want to see how your signal gets out but don’t feel like getting into a long-ish QSO just to see if your signal is being received in South Dakota. I’ve had some really memorable contacts, including the one with XE2IZN in Oaxaca, Mexico who was living in a remote, fertile valley with the indians.  They didn’t have easy contact with the world outside their community, so to hear his voice from his battery-powered 10 watt signal, to talk with him, then to listen as his signal faded into the noise was magical.

Let’s face it though, not all QSO’s are this memorable.  Sometimes you make connections with people, and other times you just don’t feel like swapping details of rigs, linears, QTH’s, and fascinating information about whether it’s raining or cloudy at each end with some guy called Bert whom you might never talk to again. Many apologies to anyone called Bert; it’s a fine name, but you get my point.

This is where WSPR comes in.  Your computer makes semi-automatic beacon-like transmissions.  They are heard by other stations, and your computer hears their transmissions also.  The transmissions include data on location, transmitter power and received signal strength, amongst other things, and all this data is automatically uploaded to a website where you can look at it.  There’s even a map of the world showing which stations are hearing which other stations.  Brilliant!

WSPR was written by Joe Taylor, K1JT, who also wrote the various protocols of WSJT, digital modes that allow for two-way QSO’s at very low signal levels.  They can be used for weak signal work on the VHF/UHF and HF bands, including EME (earth-moon-earth) and meteor scatter contacts. WSPR is also a weak signal mode.  My copy of the program regularly decodes signals down to 27dB below noise level; I hear that it can produce decodes down to 30dB. If you listen to a signal that weak on the speaker of your radio, you won’t hear anything – it’s amazing that the program can produce intelligent information from what to you just sounds like band noise!

I downloaded WSPR, plugged the line level audio output from the data port of my radio directly into an input on my sound card (not a great idea), set the radio to the frequency recommended by the program (the most popular frequency is a dial frequency of 10.1387 USB in the 30 meter band) and began receiving transmissions from WSPR stations almost immediately.  Some of the stronger signals you can hear – they sound like pure sine wave tones, though they do vary in pitch by up to 6Hz.

But it wasn’t enough to be receiving signals from 0.5,  1,  2 and 5 watt stations around the world; I wanted to be one of those stations too. If I were an impetuous lad, I could have jammed the output of my computer’s soundcard into the mic input of my FT-817 in a bid to get on the WSPR airwaves.  It might have worked, but it might also have fried something. If you want to connect your radio to a computer sound card in order to set it up for digital modes, it’s recommended that you isolate both the audio outputs and inputs of your transceiver.  What you need is an interface that will accomplish this, as well as keying the PTT line (the thing that tells your radio when to transmit and when to receive.) There are many simple circuits online that will do this – a google search will find them.  There’s even a neat one for the FT-817 by KK7UQ that can be built into an Altoids tin.  (Good grief, has anything NOT been built into an Altoids tin?)

I don’t have a good stock of parts at home, so a decision to build an interface would most likely have resulted in my buying the parts from multiple sources.  That, and the fact that I wanted this thing soon led me to the Signalink USB manufactured by Tigertronics. They make an interface for around $70 that interfaces your radio to your computer soundcard. However, for just $99, they make an interface with it’s own sound card, AND it comes with all the necessary cables. DEAL!

The advantage of having the interface with it’s own internal sound card is that you can leave the Signalink USB, computer and your radio to happily transmit and upload away, and if you want to listen to something else on your computer on the computer’s sound card, you can, and it won’t interfere with the radio transmission.  So if you want to make WSPR transmissions and check out the video of Michael Jackson’s ghost at Neverland Ranch at the same time, you can.  (No, I’m not going to provide a link for that, but it does exist.)

The Signalink USB interface is like manna from heaven.  It is pure awesomeness in a little case measuring about 4″ x 3.25″ x 1.5″ (the 4″ includes the height of the knobs.) Fit and finish are very nice and it works well.  It comes with a cable to connect to your radio (you specify which cable you need), and a USB cable to connect the interface to your computer.  That’s it.  There is no power cord – it gets it’s power from the USB cable.

Because there are so many different radios with different wiring configurations, you have to set a few internal jumpers so that the data cable will work with your particular radio.  It is recommended that you set the circuit board on a book or similiar non-conductive raised surface, so that you can perform this procedure with the front panel still attached and not damage anything. Slightly to the right of center, you can see the IC socket that is used for the jumpers:

Looking down on the Signalink USB circuit board from above, with a copy of "Walking In Britain" as a protective base.

Looking down on the Signalink USB circuit board from above, with a copy of "Walking In Britain" as a protective base.

The first 2 jumpers have been installed.  See how sitting the circuit board on a book or other raised protective surface will prevent damage to the circuit board and front panel assembly when you press down on the socket to insert the jumpers:

The board with 2 of the jumpers inserted.

The board with 2 of the jumpers inserted.Here's the board after the insertion of 2 of the jumpers:

All jumpers have been installed, and the board and front panel assembly are slid back into the case:

The board fits neatly into the rails on the inside of the case.

The board fits neatly into the rails on the inside of the case.

And here’s the Signalink USB sitting on top of my FT-817 and Z11 Tuner, for size comparison:

The Signalink USB sitting on top of the FT-817 and LDG Z11 for size comparison.

The Signalink USB sitting on top of the FT-817 and LDG Z11 for size comparison.

I have a tendency to strap things together with velcro. These are cow ankle straps that I bought from a supply company based in Wisconsin (lots of cows there!)

I have a tendency to strap things together with velcro. These are cow ankle straps that I bought from a supply company based in Wisconsin (lots of cows there!)

I started this just so that I could participate in WSPR, but I now also have a station that can handle PSK-31, Olivia, Throb, Hell, Thor, DominoEX (hey, hang on, I swear there’s a good band name in there somewhere) and pretty much any sound card based digital mode I can throw at it.  All for $99 – and I got to chat with Alex at Tigertronics too, who will be happy to extoll the virutes of Grants Pass, Oregon, and how it compares to Southern California, if you can tear her away from helping the other Tigertronics’ customers. She’s very helpful.

If I haven’t already made this clear, the Signalink USB is a well made piece of kit that will make you feel happy you own it. It’s also small, so if you own a laptop, you just might consider working digital modes on trips away from home too.

On the first night of operation, my little 0.5 watt signal was copied as far away as Hawaii and Japan, as well as in many places all over the US.  WSPR is an interesting mode. Thanks Jason.

July 8, 2009

My First CW QSO In Years

Filed under: Amateur Radio,Ham Radio — AA7EE @ 2:24 pm
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It’s shameful that I have been an extra class licensee for something like 20 years and can barely hold a coherent on-air conversation on CW. Well, to me it is.  I’m absolutely not passing judgement on any other amateurs.  I understand that some aren’t fond of CW and that, of course, is fine.  Trouble is, I’ve always really liked the idea of CW.  I stare at pictures of homebrew QRP CW rigs online and in magazines as if I were a teenage boy looking at my first images of scantily-clad women. I THINK of myself as a CW operator, even though I’m not.

So I did something about it this morning.  I heard W7GET calling CQ on 7034 and answered him.  When I heard his CQ I had this feeling that were he to come back to me, I’d have trouble keeping up with his sending, and I was right.  It’s not that I can’t copy at the speed he was sending (which I’m guessing was about 12-14wpm), it’s that I need to work on my concentration.  You see, when I answered his CQ, part of me was hoping he wouldn’t hear my little 5 watt signal so that I would be relieved of the responsibility of having to work him.  Thing is – he came back to me,  and suddenly I found that I wasn’t able to send or receive.  What was THAT all about?

Garret lives in Plains, Montana, and was very understanding of the fact that my CW skills need a lot of work.

I’m still coming down from the high of having actually had a QSO on CW.  I just heard KC6T call CQ on 7035 but I think I’ll give him a break and not answer his call.  I need to find a few amateurs for a few slow QSO’s in order to build my on-air confidence first.

Anyone up for some slow easy QSO’ing at around 8-10wpm?

Thanks Garret – you’ve given a would-be CW operator a real kick and a determination to keep trying!

July 6, 2009

On CW

Filed under: Amateur Radio,Ham Radio — AA7EE @ 7:16 am
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Something recently clicked, and things between me and the iambic paddle started looking up.

Something recently clicked, and things between the iambic paddle and I started looking up.

This is my Bencher iambic paddle. I’ve had it for about 7 years now, but have yet to use it for an actual CW contact with anyone.  Come to think of it, my last CW contact was in 2001.  I had a total of 2 QSO’s on CW that year. I’ve probably had no more than 10 CW QSO’s TOTAL since being licensed back in the late 1970’s.

What the heck have I been thinking?  Maybe you don’t think this is weird. Back in the day when the code was a requirement for gaining access to the HF bands, I’m sure that many amateurs did what they had to in order to pass the test, and then promptly forgot about the code, spending their entire amateur careers using phone or digital modes.  With the exception of the approximately 10 CW QSO’s I’ve had in the last 30 years, I’m one of them.  Now that a knowledge of morse code is now not even a requirement for earning an amateur license with access to the HF bands, I have no doubt that large numbers of amateurs don’t even learn code, and don’t ever think about the possibility of learning it so that they can use it on the air.

So what is my problem?

My problem is this.  I really like the idea of morse code. I always have.  I have spent many hours since being a teenager fascinated with radio, looking at circuits and plans for homebrew QRP transmitters and transceivers,  and thinking about how beautiful the concept is of communicating over long distances with such simple, efficient transmitters. I think QRP with CW is a brilliant idea; a fabulous concept.

I just don’t use code on the air, and the absurdity of this is starting to bug me.

For a start, my amateur activity in my adult life has not been consistent.  I operate for a year or so, then become inactive for a few years; then I start up again. During the periods when I am active, I often find that I get more enjoyment from listening than I do from actually making QSO’s, so the need for a distance-busting low power wonder mode like CW doesn’t seriously rear it’s head.  I think this is the reason, I have not been seriously motivated enough to use code on a regular basis.

I didn’t have much trouble learning the code so that I could pass the standard UK amateur radio morse code test at 12 words per minute at a Post Office testing station when I was 15.  I also didn’t experience any problems getting my code up to the 20 wpm required for the US extra class license about 10 years later.  Some folk find learning very difficult if not impossible;  I wasn’t one of them.  It came fairly easily to me.  The only reason I think that I didn’t pursue the code once licensed was sheer lack of gumption.

So things are going to be different this time.  I have always wanted to build a small and light low power transceiver for 30, 40 or 20 meters and have the satisfaction of having made lots of contacts with it. I’m going to do it this time.

Oh – and the picture of the Bencher paddle at the top of this post?  I took it so that I could sell the paddle on eBay.  I had decided that paddles and I didn’t get along.  I was going to trade it in for a straight key.  Well, I am still going to get the straight key, but for some reason, I have been practising with this paddle and have realised that I really can get comfortable with using it.

I think I just found my gumption.

Don’t wish me luck.  I don’t need it; I now have gumption!

July 4, 2009

Amateur Radio on a World War II Submarine!

This blog is a little out of chronological order.  It happened before Field Day, yet I am writing about it after Field Day.  This kind of thing shouldn’t happen once the blog is well underway, but after making my first entry, I realised I wanted to talk about this, so here we go.

The weekend of June 6th and 7th was the annual Museum Ships On The air event in which historic vessels take to the amateur bands. I met Bill KF6RMK on the Mount Diablo repeater the day before the event began and he invited me to take a look at their event station aboard the USS Pampanito. Well, I had never seen a WWII-era submarine, so the next day, my friend Antoinette and I took Bart to San Francisco to take a look at this sub which is anchored at Pier 45 at Fisherman’s Wharf in the city.

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Bill KF6RMK in the operating position of the radio room aboard the USS Pampanito.

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Dennis K6ZJU in the radio room aboard the USS Pampanito.

At the back of both pictures, you can see the original equipment (all I understand in working order – and it is fired up from time to time).

To the left, hidden away in a cabinet is the more modern amateur radio equipment that is used to put the Pampanito on the amateur bands.

Antoinette was sufficiently interested that she is now thinking about getting her tech license. Go Antoinette – and talking of Antoinette (also known as Mixtress 9 of KALX Berkeley), here she is on the sub as well:

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A most interesting afternoon. Thank you Bill and Dennis – and make sure to look out for the USS Pampanito, NJ6VT. They operate on the second Saturday of every month, and during special events.

Field Day 2009

Filed under: Amateur Radio,Ham Radio — AA7EE @ 4:13 pm
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I was originally licensed in the UK in the late 1970’s, and earned my US license about 10 years later.  To this date, I had not ever attended a Field Day event.  Granted, my amateur radio career has seen many extended down periods, and I am much more of a solitary type than one for group activites, but even so.  Pretty shocking! This Field Day was going to be different.

My current home is not a great radio location.  I live in a ground floor apartment with a balcony. Luckily I am a little elevated with a clear view to the west and southwest, over the San Francisco Bay, the city of San Francisco and then out to the Pacific Ocean.  This is good for reaching places like Hawaii, Australia and Japan with my little QRP signal.  Here’s a view from my balcony looking out over the city of Oakland towards San Francisco.  Even though I’m living on the ground floor of my building, it is a little higher than the neighbouring building to the west, so I (and my antenna) can see clearly to in the direction of all that lovely DX over the ocean!

What My Vertical Sees

What My Vertical Sees

This is my main antenna for HF.  It’s a Buddipole configured as a vertical.  You can see the zipcord radial sloping down toward the bottom left side of the frame. Anytime I want to change bands, I just pop out onto the balcony, adjust the arms, loading coil tap and whip length (depending on band), attach a new radial, fiddle around a bit with the tuning, helped by the MFJ-259b  SWR Analyzer, and bingo – I’m on another band!

This Buddipole antenna is great.  More on it in another post.

Not a bad view for an antenna eh?  If you stand on the ground in my back yard and look at the antenna, it’s a different picture though:

View of my antennas from the back yard of my apartment building.

View of my antennas from the back yard of my apartment building.

You can’t see it, but it’s a 4 story building, with the upper floors tiered away from me.  Although you can’t see it, the top of the antenna does not have a clear view over the building, it is actually blocked by it.

Oh well, you can’t have it all, unless you live on a mountaintop.  I really hope to live high up in a good radio location one day soon.

To the left is the Buddipole, and to the right is a 2 meter Slim Jim made from 450 ohm ladder line and enclosed in a PVC pipe painted green (to protect it from UV and also to make it a little less obnoxious-looking to the neighbours, although they don’t seem to care,  as far as I can tell.

So anyway, to get back on topic,  I decided that for Field Day, I was going to climb up somewhere high and kill ’em all with my QRP.   The highest point locally is Vollmer Peak.  It is in Tilden Regional Park in the Berkeley Hills.  It is at 1902 feet above sea level.  I’d been there for the first time during the ARRL VHF QSO Party and had a great time, so decided that I would do a little field day operating from there for Field Day 2009.

Fellow QRP operators – this piece of advice especially applies to newer operators;  if you ever get a little discouraged by the fact that making contacts can be a little harder using low power, whatever you do – don’t throw in the towel and buy a QRO rig and a linear – grab your QRP gear and find a nice high place to operate from.  You’ll be amazed how great your modest signal sounds to others when it’s coming from the top of a mountain!  If you ever want a panacea to cure the “I can’t make no QRP QSO blues”, the quickest way to do it is wait for any contest weekend that includes a VHF band, go sit on a mountaintop, and operate.  5 watts of signal on 6 meters, 2 meters or 70cm will get you lots of contacts and quite a few comments on your strong signal.  It feels good to be at the receiving end of that once in a while!

Back on track.  I took the bus from my home to the Brazilian Building in Tilden Regional Park and then hiked for an hour to the top of Vollmer Peak.  I didn’t take my camera with me, so no pictures – maybe next time.  This was obviously a good radio location, as there are two buildings at the top containing all manner of transmitting gear, and lots of antennas on towers outside them. Bingo – I had hit radio paydirt!  I strapped the Buddipole to a fence post, configured and tuned it for 40 meters (thank you MFJ-259b SWR analyzer) and lay down for a nap, as Field Day didn’t start for another hour.

Fast forward an hour – FD starts.  I try in vain to make contacts on 40m, but keep getting beat out by other stations.  Shucks – so much for mountaintops.  I QSY’ed to 20 meters and things looked up – 8 contacts in 45 minutes – definitely not a swift contest pace, but I’m having fun, which is the big thing. Then I QSY’ed to 6 meters, and maaan, did things heat up – people were actually calling me.  I was having QSO’s as fast as I could scribble them in my temporary logbook.  I did take a few breaks in the next hour to walk around and exercise the legs, nibble on a Clif bar, look at the view etc. but still managed to make 22 contacts on 6 meters in an hour.  Several stations commented on my great signal. It all made up for the many hours I had spent at home trying to work DX with 5 watts of SSB from a compromised location!  I then QSY’ed back to 20 meters for 3 more contacts and feeling well satisifed, called it a day. I still had an hour hike down a trail, and an hour on the bus,  and was starting to run out of water, so it was time to split.

I spent about 12 hours out of the house, with 2 hours hiking up and down hills, an hour of napping on top of a mountain, and 3 1/2 hours of operating – a totally worthwhile day!

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