Dave Richards AA7EE

August 21, 2012

Rest In Peace My Dear, Sweet Chloe-Rug

Our sweet little kitty passed away on Sunday morning and the place feels terribly quiet without her.

I took her in as a stray a year and a half ago. We didn’t know anything about her – where she came from, who her previous owners were, or whether she even had previous owners, though she wasn’t feral so I think that she did at some point.  I still remember how fast Ruggie would run towards us when she saw us. She came at us like a bullet, lay down at our feet and rolled around, showing us her tummy, just crying out to be picked up and petted, which of course, we did. She was so desperate to get inside the house. The first night we let her stay inside, she curled up on a cushion and purred all night long. I think she might have slept, but I do know that every time anyone entered the room, she was purring loudly. She was just so happy to have a safe place indoors to sleep. How could we not take her in?

My sister-in-law is a cat lover, but she already had 2 cats that weren’t exactly friends with each other. Adding this particular kitty to the mix would have created a problem. I volunteered to let her stay with me but firmly stated that I would only keep her until we found her a new owner. She knew some people that might be looking for a new kitty and I was hopeful that one of them would want this little furry bundle of purring and friendliness. They didn’t.  I took her to the local SPCA thinking of giving her up for adoption, but it was obvious that she’d be one of a sea of animals all waiting to be adopted. I wanted to know who her new owners would be, and I actually wanted some say in the matter but was told that once I surrendered her, I would not know anything more about her.  Even though I kept telling myself that I didn’t want to be a cat owner, I certainly wasn’t going to leave her there, and walk away never knowing her fate. I guess at that point I was already falling in love, but didn’t yet know it.

There were other local adoption agencies that would allow me to at least know who she was going to, but I didn’t pursue that option. Deep inside, I wanted to keep her but hadn’t yet admitted it to myself. Slowly, the little annoyances became part of her appeal. I had to cover my bed with towels and my nice leather sofa with an old comforter to protect them from scratching and the occasional throwing-up incident. My room didn’t look quite as nice as it had before, but what I began to realize was that it was beginning to feel more like a home with this adorable little creature as resident. My partner Antoinette, who lives just a mile away, wanted to call her Chloe, and I wanted to call her Rug, so we called her Chloe-Rug.  On an everyday basis we called her Rug, Ruggie, Rugster, Rugsto and other variants on her name. Occasionally we’d call her Chloe, but most of the time it was simply Rug – and boy, did that little Rugster work her way into our hearts.

Every morning she would do her best to wake me up for her breakfast. She was a mainly wet-food kitty, so I didn’t have the luxury of leaving dry food out for her at all times and leaving her to take care of herself. Nope – just before first light every morning, she would jump onto the bed, meow, then sit next to me purring and waiting patiently for me to get up and feed her. If I didn’t do that, her next move was to jump on the desk and start punching away at the computer keyboard keys. I guess she must have seen me do that all day, and figured that the computer was something that was important to me, so if she messed about with something that obviously was an object of my attention, she knew that she could get my attention too.  Most mornings it worked but on the days that I really didn’t want to get out of bed at around 6 to feed her, she moved to part 3 of her plan, which was to start knocking parts from my latest home-brew project off the shelves above my desk. She was smart and just KNEW that once she started knocking radio parts off the shelf, I would be up and out of bed within seconds. Smart little kitty! I could never get mad at her. If you’ve ever watched a little cat clatter away at keys on a keyboard, or knock things off a shelf just to get your attention, even if it happens before you’re fully awake, it’s just one of many things about pet ownership that will open your heart. Many a morning I was shuffling around, barely conscious and feeling slightly grumpy, but with my heart open and full of love for that little creature.

After her breakfast, she would sit patiently next to me while I ate my yogurt, knowing that I would leave a small amount in the dish and then place it by her side. Some mornings, we’d have our yogurt together on the balcony. If I sat at the desk with a bowl of cold cereal, she’d smell the milk, jump onto the desk and sit down patiently right next to the bowl while I ate. I knew what she was waiting for, of course, and would leave just a couple of teaspoonfuls of milk in the bowl. She was so good – she’d wait until I backed away from the bowl before taking that as a cue to move in and have her milk. She never wanted much – barely more than a taste, before she jumped back on the bed and curled up for another nap.

I spoiled her in a way that some pet owners wouldn’t agree with, but it was just her and I living together, so no harm was done to anyone else (unlike the outcome if you spoil your children when raising them). After eating her food on the kitchen floor, she would invariably leave her dish after a few minutes and jump onto the bed or sofa, waiting for me to move the dish up there so she could finish her meal in the ambience of those more exalted surroundings. She had a lifelong problem with her digestion and quite frankly, I was happy to do anything that would encourage her to eat. Even first thing in the morning after dragging my weary carcass out of bed to put a dish of food on the floor, after 5 minutes, she’d jump on the bed and start meowing again, just as I was going back to sleep. This was my cue to get out of bed again and move her dish onto the bed so she could finish her breakfast at my feet while I attempted, usually without success, to get a few more winks.

She had many little quirks of behavior that made it all the easier to love her and since she’s been gone, I’m realizing more and more how very much I did love her. It will seem a bit silly to many people who have never owned a pet, but little Ruggie was very important to Ant and I. When Ant woke up in the morning and called me, one of her first questions would be “How’s little miss Ruggie?” to which I’d reply with an update of her activities so far on that particular day. Sometimes there was a funny story to tell, like the morning that I walked to the bathroom in bare feet and stepped in a little Ruggie dingle-berry while still half-conscious.  It took me a few seconds to realize what the squishy feeling between my toes was. More often, I’d simply tell Ant whether Rug had yet had her breakfast, how well she had eaten, whether she was now lying on the bed giving me her famous “I’m the queen of this territory so please keep a respectful distance” look,  or perhaps sitting at my feet meowing for food. She had many little behaviors, all of which were very, very endearing.

I hope you don’t think this is too much information, but The Rugster’s bathroom habits were quite comic at times.  When performing a number 2, at the very moment of finishing, she’d leap out of her litter box and fly down the corridor, turning the corner into the main room at high speed, whereupon she would race around the room with her tail high, executing a kind of “victory lap”.  Unfortunately, being a long-haired cat, she didn’t always successfully complete her mission in the litter box, and while turning that corner at much velocity, a dingle-berry would fly from her rear end, only to be discovered by my feet at some later time.  We loved her all the more for these little mishaps.

She was a good radio ham too. She was my assistant op in the 2011 Zombie Shuffle:

We never got very high scores in contests though, despite her valiant attempts to dig the weak ones out of the noise:

We don’t want to say goodbye to you Chloe-Rug, but we have to.  We’re both finding this hard to deal with, but I’m hoping that time (and it has only been 2 days so far) will make things better. Our lives were so much the richer for knowing you, and I wish so much that we’d had a lot more than 18 months together.  From my initial conviction that I didn’t want a cat,  I changed to thinking of my future life with her and knowing that wherever I went and whatever I did, Ruggie was going to go on that journey with me. It hurts to know that she won’t be able to do that now. She left us far too soon.

Rest in peace my sweetie, and thank you for opening my heart.


July 27, 2012

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

A view of the underside:

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

Another point I wanted to mention is that even though the Hi Per Mite employs an LM386 for the AF amp, it is used in the low-gain configuration. Because of this, you don’t hear any of the hiss that is heard in other simple receivers that employ a 10uF capacitor between pins 1 and 8 for high gain. This is a surprisingly pleasant receiver to listen to.

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

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

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

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

This one is a little shorter:

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