by Ĝan Ŭesli Starling, KY8D
Home: ky8d.net/free
The SKCC side-swiper key by LnR Precision is beautiful in appearance as well as comfortable to the fist. Sadly, though it gained a notorious reputation among a certain fraction of users for producing in their particular rigs a most objectionable CW tone. To my own ears, noise on a par with a cat dragged by its tail across rusty sheet metal.
Probably it doesn’t cause that sound on ultra-modern HF rigs, which are said to pass only just a few paltry microamps through their keying circuits. But my sole HF rig, purchased new in 1982, is an Icom IC-745. An ideal CW rig at the time, and dependable across the years. A rig which is perfectly happy with all my other telegraph keys: Bencher BY1 and Begali Simplex paddles; Chinese K4 and Begali Camelback straight keys. So that never until plugging in this, my first ever side-swiper key, had I earned less than a 9 for tone on a signal report.
But that is what happened three tries in a row my first time out on the SKCC side-swiper key, after which I gave up on it for a while. The final poor signal report came with a verbose description of the scratch much like the one I gave above. A scraping sound. A horrible scratching. An ear-grating harshness.
Not that I couldn’t also hear some part of that in my own earphones. But only ever during TX. Never ever during practice with the rig’s switch set to RX. Not until first taking this key on-the-air … that after many hours of practice … did the problem make itself known. Initially, my hope upon first hearing the cat-scratch was that it might be an auditory artifact only just within my own earphones. Alas, it was not.
|
|
Soon I learned that I was not alone. This particular key is known for its cat-scratch tone to others as well. That to one side, LnR Precision's design is well executed, simple and elegant of aspect. Plus I’d grown very fond of its feel during many prior hours of off-air practice. And topping off all, the key had come into my possession bearing a most distinguished provenance. I’d bought this key second hand, in excellent condition, from none other than David J. J. Ring, N1EA (ref. Rescue of the MS Prinsendam, 1980-10-04), who still retains not only a hand-made Kungsimport SAG sideswiper, but also the granddaddy of all, an original Brunnell Double Speed Key. These as featured at top-of-list for North America on the Sideswiper Net website. Reasons enough that I formed a determination to fix whatever it was needed fixing, thus to soon be using this elegant and provenance-honored key on the air.
The technical issue, as turns out, is entirely to do with the key having steel-on-steel electrical contacts. That is to say, a spring steel lever making contact with stainless steel screws. Dissimilar metals, both mildly resistive. A configuration exacerbated by geometry wherein the rounded-off screws make electrical contact against the flat blade at an interface point infinitesimally small.
Quite reasonably, readers happy with this same key will leap to blame my own failure to clean the key’s contacts. But I did that first thing. And it didn’t help. I tried that several different ways. My final attempt at a points-cleaning cure involved repeated application of several Q-Tip swabs: the first made damp with acetone, the second with dilute phosphoric acid, the third with dilute ammonia, and a final with acetone once again. The same procedure recommended for surface cleaning prior to the application of strain gages. Which is something I do at work, and so have a kit. End result? Squeaky cleanness reduced the key’s cat-scratch tone in no way whatsoever.
Nor was the problem a result of contact bounce. Firstly because the cat-scratch tone would endure throughout the whole of an extended key-down (erm … -push, -pull, -lean?). And secondly, because insertion of increasingly large RC time-delay constants also offered no improvement.
The only significant factor is that the ear-bleed-inducing scratch was not ever to be heard during practice on the same rig (my one-and-only) while the switch was set for RX. But always scratchiness manifested itself whenever I might switch to TX. And it was for this disparity, perfectly repeatable, that I embarked on several EMI/RFI snipe hunts, as follows: bypass capacitors of increasing size; a series of small, type 31 ferrite torroids slipped over the shielded connecting cable; ten full turns of that cable through a much larger ferrite torroid. None of those made any slightest difference. Not even with all of those in play and my antenna tuner switched to dummy load.
The best I am able to surmise is that the issue might be current-related: that my IC-745 asks a great deal more of the key during TX than do whichever rigs the key’s OEM tested their prototype on.
So, then, how to go about fixing that? Any number of ways, as turns out, since others have solved this same problem before me. But as for myself, I didn’t much like their solutions. Or perhaps, I just wanted an excuse to toy with the problem alone by myself. Whichever that was, having met with complete success, I’ll here inflict an innocent public with yet another how-to instruction.
The goal is to supply that spring steel blade with contacts adequately conductive. I went with copper, that being both handy and cheap: two small coin-shaped discs, one for each side. And to affix them, I chose glue: a special type of two-part epoxy where both the resin and hardener are silver in color owing to a large component of actual silver.
In the photo you'll see two coin-like discs cut from 3/8th inch OD copper rod. Mine were cut on a metal lathe using a bit. A machinist friend at work very kindly offered to do this for me during his break. Not that I couldn’t have done it myself. But why refuse such a generous offer? And never mind that it might be born in some small part from needless fears for what might happen if an engineer were permitted to lay clumsy mitts upon a precision machine tool.
If at home without such a resource, I could have instead improvised a make-shift lathe by clamping a hand-held electric drill in a vice. And likewise improvised a cutting bit by pulling (never pushing) a hacksaw blade against the direction of spin. At worst it might have cost me several minutes searching the floor for where my piece had gotten off to after hitting the ground while still spinning.
Inexplicable, therefor, that any group of a half dozen 30-year career machinists should find it more tactful to offer cheerful assistance on their own time in preference to suggesting engineers don’t have a clue what they’re doing. Anyhow, the rest of it I did by myself. Unsupervised and without loss of any body parts which I did not have to spare.
Anyhow, the next step is to smooth both sides of each freshly cut disk. How I did was to chase them around with fingertip pressure on 320-grit emery paper. Plenty good enough, only just that. At least for the side which is to be glued.
As for the side which is to be an electrical contact, that needs to be as smooth as can be. Also, just a wee bit rounded. I used a Dremel tool fitted with an already half-used Cratex wheel (McMaster-Carr 4919A321). I strove for a mirror-like surface.
|
|
First, a warning. Copper is very soft. Treat it most gently.
The steps above are sufficient to deal with the key’s main problem. The key being supplied with pure copper contacts in place of steel, that sound of cats on a steeply sloped sheet metal roof is hopefully now gone for ever.
And yet... I had noted, meanwhile, two or three other things that could clearly do with upgrading about this key. So while I was at it, I dealt with those also. So if you got right to it without first reading all the way through, you’ll note that you have a few of my listed supplies now left over. Below is what I did with those.
I didn’t very much like this key’s cable connection. My first complaint is for how one post makes electrical contact with the aft blade standoff. It is hard not to fault the OEM for here for certain aspects of their design. Upon disassembly, I found that the electrically isolated wire-attachment post made electrical contact to the (admittedly pretty) aluminum blade standoff by way of a small, brass tab, the end of which sandwiched between it and a clear plastic insulator. Said insulator, for being made from a distinctly fragile clear plastic, exhibited a number of cracks due to the tab introducing a major stress riser between it and a strong clamping force. I call that a major no-no. Hence the several cracks already present.
way was I going to reassemble the key without first re-designing that. I was of half a mind to replace the insulator itself. But as it was only cracked, not fallen to pieces, I didn’t go to the bother. If later I find repair to be needful, I’ll simply cut that same shape out from a left-over sheet of 1/8th inch thick, grey silicone, 50A durometer, (McMaster-Carr 5781T59). Alternately, one might make a mold by pressing the broken pieces into Silly Putty, then afterwards pouring in two-part urethane. Or simply 3D print one.
As for doing away with that stress-inducing brass tab, again I decided to replace with pure copper. That because I had already on hand a quantity of pure copper foil. Left over, that was, from a project more than five years ago. So three cheers for hoarding! The rest is straight-forward; so for brevity’s sake, I’ll switch to third-person voice for the indented lists of dry instruction below. Here goes...
LnR using a little brass tab for a bridge was a deplorable design feature. A major cheap out that couldn't have saved more than ten cents on total cost. Replace it like so...
|
|
I find two minor faults with the key’s original binding posts. Firstly is that one of them has clearly required ex-post-facto trimming in order to fit. That for an interference fit against the side of the blade standoff. You can see where the circumference of only just one from the pair has been turned down on a lathe so as to allow shoehorning it into place.
|
|
Secondly, I just plain dislike them because of how they rely upon tiny, brass lock-washers so as to align the wire feed-through holes fore-to-aft. And thirdly, because of how the posts are somewhat too wide for any normal size of fork type wire terminal to fit underneath. Nor can ring terminals be employed because of how the twist-down tops do not come off. In short, they are just too big. That and also mismatched, one to the other, because of re-fit trimming.
Lastly, I don’t like how they sit perched proud of the base atop those tiny brass washers. It’s almost as if they designed for one part, then later substituted another.
|
|
|
This is not really all that tricky. Proceed like so.
|
|
With the key plugged in, twang the lever in one direction. Did you get an accidental dit from the bounce? Back off the screw on that side one full turn. Twang again. If no stray dit, stop. Repeat for the other direction. Thus is how I set for minimum spacing. I got used to that very quickly and feel no need for it to be any wider.
Although a bit new to the art of sideswipery myself, I’ll still describe what seems most comfortable to me. It’s a somewhat different hand posture from what I am used to on paddles. On the cootie, how I do is like this. With thumb and index finger aimed at a somewhat downward vertical, I waggle back and forth from the wrist. Lightly, so as not to bang the cootie around on my desk even slightly.
Since there is no option of squeeze mode as for full iambic on paddles, less finger flexing is therefor required. And whereas on paddles I stroke slowly with the pad of either index or thumb when sustaining a series of dits or dahs, that must be done instead by wrist waggling on the cootie.
Nor, after a bit of practice, does it cause any confusion to begin a letter with either index or thumb. The trick of that, so I find, is to play it by ear, paying no attention at all to what the hand is doing. Having my wrist at a completely different attitude than for the paddles keeps the two systems separated wherever it is they are stored in my brain.
Anyhow, that’s what seems to work best for me. The cootie, I must say, is very relaxing. No one should get so very relaxed however, as to develop a swing. I can’t help but shun the idea that one type of key should sound to receiving ops in any way differently from another. Surely the highest flattery is when one’s receiving op declares no detectable difference in one’s sending on various keys. Correct timing is always the goal. I should be very pleased with myself if one day it should be accused that I was sending CW via a keyboard.
Try to minimize this, please. Deliberate off-timing is lid behavior, no matter how experienced the op. Allow me to relate a case in point.
Once long ago, on the ILERA net, there was a control op who left his bug adjusted for 20wpm dits while working the net with spacing and dahs sent manually at just 16wpm. Being the control op, he inflicted his swing upon one and all every Sunday for all the months that I was a participant. This was circa 1989, not long before the start of my 26-year QRT. I’d held an Extra class license for almost five years. In English I could endure such CW accents with not too much trouble. But in my second language of Esperanto, the control op’s pronounced CW swing strained my attention to its limits. And for being deliberate, I considered the behavior exceedingly rude.
Therefor I pounce … yes I do … instantly upon any suggestion in Facebook posts that the sound of a cootie deserves any praise for its ‘musical swing’. Melodious or not, deliberate swing is a very, very bad thing. So let’s try and avoid that, okay? Granted, there are special cases. Medical reasons and such like that. All very well. But not as a deliberate affectation. It’s the same thing exactly as affecting a foreign accent during normal conversation. Whosoever does that for no explicable reason is seldom very well thought of. It really is quite the same thing.
Latin for “Let the moocher beware”. I composed this for me, and employed it with glee. I share it here with you for free, but offered without even so much as the smell of a dead warranty (or wheriot, as the case may be). Whatsoever disasters of cosmic proportion as may result from the use of this information, any and all culpability rests wholly and solely with the user.
My contact email and postal address are on QRZ.com for call sign KY8D