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.

August 9, 2012

Adjusting The Crystal Filter Settings On The K2 And Achieving Maximum Intelligibility with Narrowband SSB

Filed under: Amateur Radio,Ham Radio,QRP — AA7EE @ 9:48 pm
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When I first built my K2 about 8 months ago in November and December of last year, I initially set up the variable bandwidth crystal filter as per the suggesting settings in the K2 manual.  Shortly afterwards, I downloaded Spectrogram v5.17 and followed the filter set-up procedure described by N0SS on this page.  Incidentally, as of the time this post is being written, the page that is linked to for downloading Spectrogram no longer has the download. Version 5.17, the last free fully free version, is more than adequate for setting up the K2 filters and it’s still available if you look around the internet a bit.

I did reasonably well aligning most of the filters but noticed while on the narrowest CW setting – 200Hz, that it attenuated the signal quite a bit. On looking at the response curve in Spectrogram the other day, it became obvious why. Tuning the receiver so that it received a tone of 500Hz (my selected frequency offset) placed the signal halfway down the lower skirt of the pass-band of the filter. Heaven knows that I was thinking. With every other bandwidth I had set up, the filter pass-band was centered nicely on the 500Hz mark, but the 200Hz filter pass-band was way off.

This incorrect filter setting had arisen as a result of  a misunderstanding of the way that the K2 filter adjustment process works. I don”t understand exactly what is happening inside the K2 during this but the best way I can currently describe it is as follows: When adjusting the BFO frequency for a particular filter setting in order to move the passband, the CW note (or pitch of the SSB signal) also changes. When you move to the next filter setting, or hit the menu button to finalize that particular setting, the BFO frequency is re-calculated, and you will hear the signal at the correct pitch again. Call me slow, but I wasn’t noticing that recalculation step. As a result, I was reticent to move the filter pass-band very far during adjustment of the settings for fear that once they were finalized, as I stepped through the different filter settings, the CW note (or SSB signal pitch) would change significantly. What a handicap my misunderstanding presented!

The other difference in the way I was adjusting the filter settings this time around was that instead of using band noise, I decided to build a simple wideband noise generator. The circuit is described by N0SS on this same page on the Elecraft site.

Boy, I like simple circuits. The ubuiquitous Altoids tin was the way to go for this one. I could have built it ugly-style, but the MeSQUARES are so easy to use.  No need for a circuit board – I just glued the MePADS directly to the tin and used the tin as the ground plane:

Here are the Spectrogram plots for the 4 CW filter settings I chose.  For the widest one, 1000Hz, I didn’t center the filter pass-band on the 500Hz mark, as that would have placed part of the filter response curve on the other side of the BFO signal,  meaning that the receiver would no longer be a single-signal receiver. For this bandwidth, I placed the 500Hz mark (indicated by the vertical red line) a little to the left of the center of the pass-band. Although the nominal bandwidth of this setting as reported by the K2 was 1000Hz, I estimated the 3dB b/w as about 500Hz and the -6dB b/w about 690Hz:

The nominal 700Hz b/w was closer to 335Hz at the -3dB points and 440Hz at the -6dB points:

The nominal 500Hz bandwidth looked to be about 250Hz at the -3dB points and 380 at the -6dB marks:

While the 200Hz nominal bandwidth checked in at the only slightly lower figure of 240Hz at the -3dB points and 340Hz at the -db points, it sounded a lot narrower than the 500Hz nominal setting. This was only an estimate.  The shape of the curve in Spectrogram is not static – it does move around a little,  so there is room for variation in the measurements:

I’m really happy with the way the 200Hz setting sounds. It’s a shame that it was incorrectly adjusted for so long.  I had read that the signal is attenuated if you wind the filter down to 100Hz, so I assumed that the attenuation I was experiencing was normal. Turns out it was normal – for a filter in which the signal is centered halfway down one of the skirts! This got me thinking about the small number of complaints I’ve read from K2 owners who say that their K2 sounds terrible, and can’t help wondering if they have not yet learned how to set up their filters properly.

Which brings me to the next part – adjusting the filters for SSB. I never used to think of anything other than bandwidth when thinking about filters. For some reason (and this is evidence of my particularly inflexible way of thinking) all I thought about was the width of the filter. “How narrow is it?” was my only question.  I never gave much thought to the importance of exactly where in the pass-band the BFO is placed. Once again, I don’t know why. I seem to never pay attention to things until I’ve been beaten over the head with them many, many times.

Things aren’t so critical if your SSB filter is 2.5KHz or wider, but as you dial the pass-band of your SSB filter down it can get pretty hard to retain good intelligibility.  I Googled the general subject and found this really interesting article by G8JNJ titled “Improving the Intelligibility of SSB Transmissions”.  Originally published in Radcom in Feb 2009, it gives some good tips for achieving the maximum clarity of SSB transmission and reception in the limited bandwidths we amateurs use.  To simplify, the article says that the range  up to 8KHz is all that is needed for intelligible speech.  Trouble is, we amateurs use bandwidths of much less than that.  In western languages, most of the energy in the vowels takes place under 500Hz. The vowels are what help another person determine that it is you who is speaking – they do a lot to give your voice it’s unique identity that makes it sound like your voice.

That’s all very nice (and it is) but the vowels don’t contribute anywhere near as much to intelligibility as the consonants do. Consonants occur at higher frequencies than the vowels, and the range 800 – 5000 Hz is particularly important. That still represents a bandwidth of 4200Hz though.  Going further, Martin says that the area around 1600-2000 contributes the most in terms of consonants.

Now we’re getting somewhere.  So the range from 800 – 2000 Hz is particularly critical. That’s a bandwidth of just 1600Hz!

I didn’t follow these figures faithfully when adjusting my settings for the SSB filters in the K2, but I did follow some general rules based on what I had just learned. Incidentally, I don’t yet have the KSB2 SSB option for the K2, so am using the CW filter to receive SSB:

The wider bandwidths were easier to adjust. I set them to allow more bottom end and as a result, they are more pleasant to listen to. By the time I got down to the 1600Hz (nominal) setting, I had to set the lower cut-off at about 800Hz to achieve maximum intelligibility.  Without having first read the Radcom article by G8JNJ, it wouldn’t have occurred to me to set the lower cut-off so high, but I was surprised at how clear the audio is at that setting, even if it’s not really that pleasing to listen to.

In the following screen captures, the markers are set at 300Hz and 2500Hz. That doesn’t mean anything – they’re just markers to show you where the 300Hz and 2500Hz points are, in case that helps you to interpret the filter response curves. The 2490Hz (nominal) setting was easy. The -3dB point at the lower end looks to be around 300-400Hz. It sounds fine:

As we go down in b/w to the (nominal) 2200Hz setting, the lower -3dB cut-off looks like it’s around 450-500Hz (my rough estimate only). It definitely sounds more restricted at the lower end but still has plenty of clarity:

The 2100Hz response curve looks very similar. I’m not sure why I picked 2 bandwidth settings that are so close to each other. I may well change this:

Look at the 1600Hz (nominal) setting. I’ve set the lower -3dB cut-off point to what looks like around 800-1000Hz.  There’s a lot less fidelity than the wider filter settings, but not much less in the way of intelligibility:

I’m pretty sure that at some point in the next few months, I’ll be building the KSB2 SSB option; not so much because I want to become active on phone, but more because I’m interested to see how the filter compares to the CW filter in the basic K2. The CW filter does have quite a bit of ripple in it at the wider settings, and it’ll be good to have an SSB filter with a flatter top to the response. I’m also keen to spend a little time setting up the transmit audio to see how it sounds. It wouldn’t hurt to have the SSB option fitted.

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