Saturday, April 28, 2012

Adding the A743 to the A3S

Unfortunately, I don't have any pictures to share of this, but Jerry NG6R's question this week reminded me of the ordeal -- so I figured I should share it with everyone. 

I added the A743 to the A3S in September of 2005. The A3S had been up on the tower for four years at this point. I remember running into some difficulty with this update.

  1. Remove Rotator - rather straightforward. Loosen the rotator clamps and lever the mast up a centimeter or two before tightening down the clamping screws on the tower top. Remove the rotator clamps, screws, unhook the rotator cables (you did use a weatherproof connector for this, didn't you?), and pull the rotator out. I think I attached a sling to the rotator and hung it off the side of the tower using a carabiner for the duration.
  2. Lower Mast and Antenna to Top of Tower - this step always makes me nervous, as I always think the 70+ lbs  of mast, antenna and whatnot is going to come crashing down suddenly and impale a foot, hand or arm as I loosen clamping screws in the tower top.
  3. Remove Driven Element. First loosen the U-bolt and swing the element up vertically. I then attached a sling just above the boom and then removed the U-bolt. (This way, the element can't get away from me an go crashing to the ground) Then attach to a rope and lower to the ground.
  4. Update Driven Element with A743 Components. Be sure to follow the tips in my original article. I used the dimensions half-way between CW and MID in the manual. Double-check your dimensions. Take care to avoid bending the capacity hat. Go ahead and attach the driven element support rope clamps, and tie the rope to one clamp. You can't tie the other side, since it has to go over the boom.
  5. Mount the Driven Element. This bit was tricky. The element is much harder to haul up the tower, since you have to avoid snagging the capacity hats. Bring it up vertically and attach the U-bolt, but don't tighten it down just yet. Toss the support rope over the boom and swing the driven element up so you can climb down and tie off the support rope. (Don't forget to put the support rope through the grommet on the support mast) Rotate the driven element back down to horizontal. The Driven Element is strong enough to support itself, at least in the short term.
  6. Mount the Driven Element Support Mast. Hardest bit. The amount of slack in the rope depends on where you put the support rope clamps and how long the rope is. I barely had enough slack to get the bottom U-bolt on the support mast. Once that is done you need to adjust the height of the mast to get the Driven Element level with the other elements. This is a tough operation, since you are above the tower, and have to hold the mast up with one hand and tighten the clamp with the other. Don't forget the twist in the rope. Without it, you'll be back up the tower in a year or two to replace the rope.
  7. Raise Mast and Antenna. Again a nervous operation. If your mast is heavy, you should use a come-along. Mine isn't terribly, so I used a pulley arrangement. 
  8. Replace Rotator. Reverse of the previous steps. 

Sounds simple, doesn't it? No. Well, it took me about a half-dozen climbs to finish this off in the fall of 2005, and then I had to do it again when the support rope broken. I haven't had any trouble since then.

Cushcraft A3S/A743 Performance

A3S/A743 pointed toward Europe.

Jerry, NG6R, e-mailed me this week in response to my posting on the Cushcraft A3S/A743. Jerry had sold his A3S to another ham who was wondering about getting the A743 add-on kit. He wanted me to share my experience with the antenna.

The specifications don't really change with the 40 or 30m add-on. This was true with my experience. I did the A743 update in-place, with the antenna still on the tower. (Something I'll share in another posting)

The performance on 20/15/10 was the same as before the update. On 40m, it is a dipole -- but a rotatable dipole. Beamwidth is pretty broad, about 100 degrees. There are noticeable nulls off the ends -- and some of that may depend on how high the antenna is mounted. Mine is at 15m (50 feet) high, which is still a little bit low for a 40m antenna.

If you can mount an inverted V or dipole significantly (8-15m) higher than the A3S, you might be better off with a wire antenna than the A743. At my QTH, the 15m high tower is the highest point in the lot, so the A3S/A743 is a great combination. 

In the picture, you can see the 80/40m trap dipole coming off horizontally to the left of the tower at the 12m level. This dipole is broadsize NE/SW. With only 3m difference in height, there's not a lot of difference in the two antennas, with the higher antenna having a slight edge on DX. During some domestic contests, I would rotate the A3S/A743 to point NE, giving me 360 degree coverage on 40m with a flick of the antenna switch.

(The 80/40m dipole has since moved to the micro-shack in Floyd County, GA)

Does it work? You bet. I have 40m WAS and 113 credits on LoTW for 40m, virtually all of them on this antenna. I'd prefer a two-element short 40m yagi, but my tower installation doesn't allow it. The A743 kit only adds a few pounds of weight and increases the turning radius by about a meter. It's a good addition to most A3S installations.

Thursday, April 5, 2012

K1EL K12 Keyer

Finished K1EL Keyer with Ancient HamKey
HK-1 Iambic paddles.
My 30+ year old CMOS Keyer gave up the ghost -- the point-to-point wiring apparently was suffering from a failure. I tried re-building it using wire-wrap, but the troubleshooting was taking too long. I figured I needed to quickly build a replacement keyer that I can use right now with my TS430S.

I remembered that Curtiss used to make a keyer chip. But a quick search found that the original Curtiss devices were no longer available, although MFJ purchased the rights and offers a slightly updated chip.

Honestly, at the time I looked at this, the chip was $45, which seemed way more than I wanted to spend on a "temporary" keyer. A bit more searching brought me to K1EL's web page.

K12-BAT kit, as it comes from K1EL.
K1EL offers a number of interesting devices and components. The WinKeyer I had heard of -- but frankly, the name put me off slightly, as I've been a long-time Macintosh fan. Imagine my surprise to discover there's nothing "Windows" about the WinKeyer. It looks like a superior product for providing CW keying facilities in a contest station.

But that would be a project for another day. Today, I just needed a simple keyer. And I found it. The K1EL K12 keyer chip filled the bill nicely, and had 6 programmable memories and a host of other features to boot. All for less than $10!

Even better, there was a kit -- only $17. I quickly ordered the K12-BAT and within the week had the package pictured above.

There's not even two dozen components.
There's not a whole lot to the kit -- printed circuit board, socket and chip, transistor, battery holder, and a handful of resistors and capacitors. This would not be a bad first kit for someone. For me, it took less than 30 minutes to assemble.

Finished circuit board.
Once assembled, I wired up the paddles and tried it out. The command structure takes a bit of getting used to -- it's hard to remember for some of the longer commands what comes when.

However, it is quite a serviceable keyer. But, I can't just have wires strewn all over the bench. (Well, actually, I can, but that's not how I like to operate) Digging through my junk box I found a used cast aluminum box that might make a decent cabinet. The hard question was -- what to use for the seven pushbutton switches I needed? Nothing I had in the junk box was small enough to fit in the aluminum box.

Wiring was easy.
The upcoming Dalton hamfest provided the answer. If found some surplus switches that were small enough to fit, and they were cheap, so I bought eight. A subminiature potentiometer filled out the required parts list.

Drilling out the enclosure took a more time than building the board. But the wiring was very straightforward.

All done but the hard part.
At this point, I had a functional keyer in a rather ugly enclosure. Finishing the enclosure took more effort. Removing the board switches and pot left me with an empty enclosure. You can see that it had some kind of adhesive on the top, as well as a bit of corrosion here and there.

The best treatment, I've found, for stout aluminum like this is wire brushing. The oxide and other compounds come off easily, and the steel bristles of the wire wheel score the aluminum just enough to give it a nice texture. Best not to do it in a hurry and don't use too much pressure. I did both and ended up with some deep scratches in the top and a wire-brushed left index finger.

Of course, I had to wire brush it again. I painted the enclosure with the same flat black paint I used to repair the R7000. The end result is pretty sweet.

I'm still trying to figure out how to use the K1EL K12 keyer. In trying to program one of the memories, I have found it is very, very sensitive to character timing. I probably need to read the manual again. In any case, I am very happy with the K1EL K12 Keyer kit. I would highly recommend it to anyone who needs a sophisticated, yet inexpensive keyer.