Tuesday, November 16, 2010
I didn't feel like debating the finer points of operating CW with him. I was more interested in what was on the table: three sets of keyer paddles. The first was a a Heathkit HD-1410, which I knew to have a reputation for horrible feel. One other was a single-lever paddle, which I had no interest in. The third looked to be a Bencher BY-1.
I generally go to a flea market with a list of all the different things I'm looking for. I didn't this time, but I did remember I was looking for an inexpensive set of keyer paddles. The Bencher looked like it might fit the bill.
Back in 1979, when I was licensed as N8BHE, I found the progression of dits in my call difficult to send, so I opted to upgrade from a straight key to an electronic keyer. I bought a Ham-Key iambic paddle and built my own CMOS keyer. Now, the Ham-Key isn't the greatest paddle design. The base isn't quite heavy enough, the paddle arms pivot on large pins, which leaves some slop in the feel. But in 1979, it was only $30, and I've been using that same unit for 31 years.
I figure it is about time to get a second set of paddles. If you look around, you'll find they are not cheap. There are none you can buy for less than $50, and most of them are well over $100. The item on my list read "cheap paddles." That meant finding something used, hopefully in reasonable shape.
I had used a Bencher before, back in 1980 in the Georgia Tech club station W4AQL. I remember my first experience touching those paddles. I slapped the handles so hard the armature came off the pivot. I suppose you have to use a more delicate touch than with the Ham-Key.... But I did have some success using it. This fellow had this unit marked $20. I offered him $10, then $12, and finally we agreed on $15.
As I walked away from the table with my purchase, another fellow suggested I tear the unit down completely and clean it, and it should work great. That's just what I had in mind.
Once I got home, I put the Bencher on the workbench. It was far grimier than I remembered, with a telltale film of yellow tobacco on the base and armature. During disassembly, I found the hold screws to be hopelessly bent, and one of the screws holding the round armature pedestal nearly impossible to remove. With vice grips I removed it, but this destroyed the head of the screw.
All of the metal hardware went into a small container filled with WD-40, which did a good job of removing the latent grime. I cleaned the base and plastic parts with Windex. This took off the grime, but some of the paint came off as well -- likely due to a long-standing chemical reaction of the dirt with the paint.
No matter, a couple of coats of flat-black spray paint and the base looks good as new. Then the tedious process of putting the components back together. I replaced the four screws that I could not reuse, and quickly re-assembled the unit and adjusted it to suit my fist. I followed the excellent instructions compiled by N1FN here.
The result you see pictured above. It looks great and the feel is good, too. I'm not as ham-fisted as I was back in 1980, so I haven't had any trouble springing the mechanism. The base is way heavier than the Ham-Key, so it doesn't tend to wander as much. I believe I'm really going to enjoy working CW with my Bencher paddles.
Thursday, November 4, 2010
The key to busting pileups is to listen. That's what the DX experts will tell you -- and they are right. The first thing about busting pileups is not to transmit. You can't listen when you are transmitting.
But just telling someone to listen doesn't help if they don't know what to listen for. There are several things you need to listen and find before you begin to transmit.
First, you have got to hear the DX station. If you can't hear the DX, and hear him well enough to tell exactly what he is doing, there is no use transmitting at all. This can be very frustrating when you hear him work your buddies all around, but its the truth. If you can't hear 'em, don't even try to work 'em.
Next, once you can hear the DX well enough, you've got to know where he's listening. This is easy if he's working stations simplex. But, more than likely, for any reasonably sized pile-up, he'll be operating split. And that makes things more challenging.
If you have a fancy radio that allows you to listen to two frequencies at the same time, this the next step will be easier. Basically, what you have to do is listen to the DX station on his frequency, and then find the station he's working on his receive frequency.
You don't have to have the fancy radio -- you just need two VFOs and some nimble fingers. On the Elecraft K2 I use, you can hold down the A/B button, which activates the REV or reverse feature. This causes the radio to swap the VFOs it is using for receive. So, one moment you are listening to the DX station come back to someone, then you press REV to switch to the other VFO, and then hold it down while you tune around for the station being worked. But, don't hold it too long, or you'll miss the DX station's next transmission.
Sounds complicated, eh? Well, maybe. Figure also there's no guarantee you can actually hear the station the DX is coming back to. You might have to do this over and over again until you hear one. Then you have to worry that the DX station is staying in one spot -- he might be tuning around in the pileup. But the best place to be when you start transmitting is right around the place the DX station was listening last.
Once you've done this, it is probably time to start calling. If you need to tune your amp, please move a few kHz off the DX frequency before you start.
Your calls should be short -- just your full callsign, and then go back to listening. Perhaps you do this cycle two or three times, depending on the pileup. Once the DX station comes back to someone, there's no sense in continuing to transmit -- unless that stations is you.
Even though you start transmitting, you don't stop listening.
Who is the DX station working? Is he working stations in your area, or are they all on another continent? Perhaps he's working folks from all over. Listen closely to figure this out.
Who are the stations he responds to? Are they the earliest, strongest callers, or is he picking later in the pileup when the calls die down? Is he accepting or ignoring tail-enders? Figure out the pattern that the DX station is using, and use that information to place your calls better and better.
OK, you've done all that? Now is the time to have patience. Pileups can be huge random events, and if you keep on listening and carefully transmitting, you'll eventually get through. It may be on the first or second call, or it may take a half and hour of calling with no joy. Don't get discouraged.
Even so, there are a few that get away. Propagation will change, or the station will QSY or QRT. You can't help that, so don't worry about it. Most of all, don't let your worry interfere with your operating.
Careful listening can make all the difference. I've broken several pileups on the first or second call after listening to them to for several minutes. Good listening should tell you where to transmit, and precisely when.
Don't allow yourself to get frustrated and learn to enjoy the hunt.
Tuesday, August 31, 2010
|Finished Radial Clip|
Basically, a clip consists of about 4" of 12-14 gauge copper wire, bent double, with a large enough bend radius to allow a 12-14 gauge copper wire to fit between it. The resulting clip is about 2" tall, which is about right. Any taller, and you may have difficulty pushing it into the soil without bending it.
What I needed was a jig that would make it easier to cut the wire to the right length, and then bend the clip perfectly each time, perhaps creating more than one at a time. Grabbing a scrap piece of wood and a few nails, I quickly fashioned the jig you see photographed.
The jig consists of a large 16-penny nail and a row of small wire brads. A extra wire brad is placed about 4" away from the 16-penny nail, and serves as a measuring point.
|Cutting the wire|
Next the wire is inserted between the brads and wrapped around the 16-penny nail. Several wires can be stacked at once and bent at the same time. I have the best success with about three at a time.
There you have it. With the jig it is no problem cranking out 50 to 100 clips with just a few minutes of work.
|Bending the clip|
Wednesday, July 28, 2010
Tuesday, May 18, 2010
Sunday, April 11, 2010
When calibrating the Elecraft K2 crystal filters, a noise generator becomes an invaluable tool. Using one results in clean spectrum traces. I had built an RX noise bridge some time ago from an ARRL Handbook -- the original article for that project appeared in the December 1987 issue of QST.
The noise source is a reversed-biased zener diode -- which produces noise of fairly broad bandwidth. A two transistor amplifier chain feeds the trifilar winding of the noise bridge transformer.
This circuit had the unusual addition of an oscillator to switch the noise off and on at about 1 kHz. This made for the very disconcerting effect of hearing 1 kHz tone no matter where the receiver was tuned. The noise bridge was intended to help me tune a manual antenna tuner without having to transmit, but it didn't work as expected.
The oscillator was useless for tuning the filters of the K2. I modified the circuit by removing the NE555 chip and jumpering pin 3 to pin 4, effectively supplying power to the zener all the time. (In fact, this very circuit appeared in the March 2002 issue of QST, and was also promoted by Tom, N0SS as a noise generator on his site)
However, the two transistor amplifier didn't seem to provide much output -- I got the strongest noise signal when attaching to the base of the first transistor. Perhaps this is why the tuner-tuner project didn't work so well. I suspect there's something wrong with one of the junkbox transistors I used.
My main problem was that I needed to jury-rig it with jumpers every time I wanted to use it. What I wanted was a dedicated noise generator -- which isn't much more than a zener diode noise source, followed by a broadband amplifier.
Since I didn't have much luck with the two-transistor amplifier, I thought of using something different. Mark, WA3YNO suggested using an LM703 as the amplifier. I had a better idea -- why not use a MMIC amplifier? The MMIC offers high gain, unconditional stability and an impedance near 50 ohms. I'm surprised we don't see more MMICs in amateur designs. I had a few MSA 0885's in my junkbox. Perfect.
Better engineers than I have already figured this out. If you look at the Elecraft N-gen, this is exactly what they did. So I build basically the same circuit on a piece of perfboard. The result -- S9+20 dB worth of noise. This circuit is so simple it's hard for it not to work right away. A switch is handy because the circuit draws over 12 mA from a 9 volt battery, so it won't last terribly long if you leave it on.
This noise generator works great. Make sure you don't ever transmit into it, though, as just a little bit of power will destroy the MMIC in short order. I generally use the Rx Antenna jack on the K2 (since I have the 160m module), so there's no chance of transmitting into the noise generator. Just make sure you switch the Rx Antenna off on that band, or you'll be wondering where your signals went. (Don't ask me how I know this)
Wednesday, April 7, 2010
Sunday, February 28, 2010
The Elecraft K2 has a number of unique features, one is the variable bandpass filter which can be programmed for different bandwidths. This leads to a very flexible design for CW or RTTY, but requires a bit of configuration work. For each mode, you can select up to four crystal filter configurations (FL1-FL4), including using the KSB2 module filter (OP1). The first filter configuration (FL1) is also used when transmitting.