Diy Cw Keyer
After iwo months of hightech digital communications, it seems ironic that this month we're about to build a CW keyer. But what the hell, thafs what we're going to do, This is such a simple construction project that it would be unfair to even consider il a "weekender/1 Perhaps a rainy Sunday afternoon would be more realistic.
The entire keyer is so simple thai construction is limited to two integrated circuits. The timing and logic are supplied by integrated circuits 4027 and 4011 CMOS. A printed circuit board is also available. as is a complete kit of aJI parts, including the speed pot All that js needed is a cabinet to install the circuit board. The smaH size of the PC board should make installation inside a small QRP transceiver painless. Take note, portable QRP ops: An extra box will no longer be needed when backpacking with HW-8 into the woods.
The printed circuit board is stightly larger than the 9 vott battery thai operates the keyer Don't worry about spending a lot of money on batteries either, the CMOS ICs consume such small amounts of current that there es no need
Low Power Operation for a power switch. A 9 voit battery should last about a year before it needs to be replaced. If installing Ihe circuit board inside a radio, the host will supply the operating voltage A battery will not be needed
" How many bytes of memory does it have?1 Whoaf looks like I forgot to mentions some small insignificant details. Hummm, in a word, none. In fact. \t doesn't even have dot-dash memory.
"Weil how about iambic keying?" Sorry. Not this time around. All this keyer does is make dots and dashes, except for the proper 3 to 1 timing for good-sounding CW Remember, I said only two simple ICs. K-Mart specials not large scale integrated circuits. Oh yes I almost forgot there is no on board side-tone A side-tone from the radio will have to be used to monitor the CW,
Figure one is the pan placement for the keyer This is from the component side of the printed circuit board For those that want to "roll their own/' figure two is the foil pattern for the keyer Mike Michaels W3TS did the artwork from the original schematic. Speaking of original schematics, I did not design this keyer, but rather it comes from the German publications called CO-DL The keyers schematic is shown in Figure 3
Construction is simple and straightforward. For assembly, a PC board is available or pert-board may be used. Somehow I can : imagine why anyone would choose to build the keyer without the PC board. If CMOS chips have never been used in a construction project before, some simple handling instructions are in order. Because of the high input impedance of the chips, they are easily damaged by static charges Before handling the chips, touch a gounded object to discharge any static electricity from the body.
The chaps must also be inserted in their sockets properly Pin one may have a dot beside it or me chip will have a notch on one end This is shown in the part layout If me instructions are not followed carefully, the chip may fail or cause the keyer to die. Some of the chips will have to have the pins straighten out before they can be inserted into their sockets. 1 place the chips along the edge of my work table, and press down to straighten one side. Turn the chip over and do the other side. Sockets are not necessary for this project. but it sure helps out when it comes to troubleshooting If sockets are not used, then solder the ICs directly to the board using a grounded soldering iron. Watch that the chips do not get too hot!
After stuffing the printed circuit board, check over the work for errors. Then once everything is the way it should be, connect a 9 voit battery to the keyer. Adjust the speed control to mid range, The output of the keyer ts an open-collector transistor. There shouldn't be any trouble keying either a HW-9 or HW-8, Almost all of Ihe newer solid state radios will also key properly without modifications to the basic circuit. Grid block or cathode keying will require the use of an interface between the keyer and the radio.
To test the keyer, just connect up a VOM (set for ohms) to the output and short eitner the doi or dash paddle to ground. The meter should be seen deflecting. Adjust ihe speed and notice a change on the meter. Connect the keyer directly to the radio to avoid messing with a VOM A VOM must be connected property before the operator can tell if all is well Some VOMs have the polarity reversed when using the ohm ranges Just be sure to use a dummy load while testing
After testing the results, install the circuit board into a suitable enclosure. If the circuit is being installed into a HW radio, double-sided tape will hold the board to an inside case wall. The speed control can be mounted on the rear or the front panel
Oh No! Trouble. Well there is little that can go wrong Check over the wiring once again and the placement of the components on the board. It all looks good, look at the base of the keying transistor with the probe of the VOM Close the dot paddle (or dash paddle) and see if ihe transistQf is being turned on If it is, then there might be a bump 2N2222A or a wiring error from the transistor collector to the radio.
If the base is not seen going high, then look at the clock circuit. If Ihe clock is not running, try replacing the 40it IC Check the clock again to see if it is running The keyer will not work unless the clock is running. If the is clock running. but nothing is coming out of the keyer, swap out the 4027 chip. That should fix things up.
Now for the good part: ( have collected together all the pads for this project, including the printed circuit board and IC sockets OnEy a 9V battery is needed to finish the project. The cost of the kit, will be $9 postpaid in the USA. hi throw in a copy of the enlarged parts layout guide If one of these kits are of interest, don't delayl Only 25 are being made.
The printed circuit boards included in the kit were furnished by Tom BerryhiII AB0Q from his
80 73Amateur Radio • July, 1988
"This is such a simple construction project that it would be unfair to even consider it a 'weekender V
of satisfaction, QRP has put the fun back into the hobby. Not just into operating itseEf, but in tinkering, building, perfecting, and even in the special friendships between QRPers,
Well that is about aiJ for this month. Next month we'll iook at something that everyone has thought about at one time or another:
solar power. Coming in September, the antenna issue will surely please those wire-stringers out there.
Sometime later on this year, l-ll havedetailsonatrophy I'll give away, the Homebrew DXCC award. Keep those soldering irons hot and watch for the details, BB
Is your library incomplete? Missing a key article for your QRP project? You can order back issues ($3.95 each) or article reprints ($3.00 for the first, $1.50 thereafter) Send your request to WGE offices;
Figure 2. PC board, foil side. (Not to scale)
miss out on. Sure, working BY4IY with a microprocessor controlled Japanese made SSB transceiver is great, but some hams are missing out on some of the finest traditional pleasures^ challenges, and achievements of our hobby. That's building one's own equipment- People with the talent like Tom Berryhill make it so much easier when the required parts
Ftgure t. Parts layout from the top side of the board1
company Ditek Industries, inc. Tom also provided the boards for the Two-Fer for me, and those who took up the offer to purchase one of those boards know first hand the quality of Tom's work, Tom is a mover and shaker, A welcome addition to ham radio.
This is one aspect of ham radio that, unfortunately many of us are accessible. Building a TS-940 will not give the same feeling
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