G0XAN's Hot Tips

These tips, in no particular order, represent useful snippets of information that I have gleaned from various sources or found out the hard way over the past few years. Hopefully listing them here will save you from learning them the hard way!

Learning CW
The UK Morse Test
CW On the Air
Homebrewing
- General
- PCBs
- PIC Micros


Learning CW

- I used G4UXD's Supa Tutor PC program to learn "from scratch". Some say you should listen on-air and not use a computer, but having listened to the (poor) quality of some on-air CW, I would beg to differ! This program allows you to set the speed of the characters and spaces separately and will send letters, numbers, punctuation, Q-codes, callsigns, and even some real QSO-format test messages. I have no commercial interest in this product, but I would thoroughly recommend it. It is usually advertised in the Classified Ads in RadCom, or visit G4UXD's web site for more information.

- When I was learning CW I also cycled to work. To learn the letters I would concentrate on a few at a time and learn them by repeating them over and over in my head as I cycled to and from work. I gradually worked up to reciting the entire alphabet, numbers and common punctuation on my journey.

- From Day One learn the characters at the correct speed. Use longer spaces between characters to give more thinking time, then shorten the spaces as you improve.

- Copying random characters is far harder than copying QSOs. If you can copy random mixtures of letters and numbers at 12WPM then the UK test will be a doddle!

The UK Morse Test

- The examiners when I sat my test (Picketts Lock Rally, 1995) did their utmost to put everyone at their ease. They WANT you to pass, and although they would never break the rules, they really do everything they can to help you pass.

- It IS possible to send accurate CW when you can't hold your hand still for nerves! (I still don't know how!)

CW On the Air

- Keep away from band edges, they are the haunt of DXers and speed merchants it seems. Move up about 50kHz to where things are a little less frantic.

- Try the RSGB "Slow Speed Cumulative" contests, run in the spring and autumn on 80m. There is a 12WPM speed limit and it is really good for improving your CW skills. A two-hour contest session will really give your brain a workout.

- Can't think, spell and send CW at the same time? Then write out a prompt card, especially if you live in a town with a long name. My first few QSOs consisted of repeating the overs I had just received (and written down), inserting the correct name, QTH, report etc. Very soon the CW takes care of itself and you are free to think ahead to what you are going to send next.

- Don't send your "CQ" calls too fast. You are bound to get a reply at the same speed! Everyone can send "CQ CQ DE <own call>" at twice the speed they can copy. Be aware of this fact, and make sure that you don't send faster than you can receive, because someone will come back at the same speed as you are sending!

Homebrewing - General

- Don't try to run a FET push-pull stage in Class A! It blows up when both FETs are biassed on. Be very careful when adjusting the bias point. Fortunately the FETs I learnt this with weren't very expensive!

- The GQRP Club 9MHz narrow CW filter has a horrendous insertion loss. An MMIC monolithic amplifier is a very simple and fairly cheap solution, perfectly matched to the 50 Ohms impedance of the filter.

- For an accurate 1750Hz toneburst, simply use a cheap 14.31818MHz (TV) crystal divided by 8192 (a CMOS 13-stage binary divider). A simple passive RC filter will give a reasonable sinusoid. The actual toneburst frequency will be 1748Hz which is close enough for every repeater I have tried.

- For a simple audio sine-wave generator, use a Twin-T oscillator. It can be built with either a transistor or an op-amp, and uses only resistors and capacitors - no thermistors, light bulbs, inductors, negative resistances or other black magic, just two phase-shift networks. It can be found in many books, including the ARRL Handbook. More details...

- To avoid breaking expensive small drill bits, start all the holes by turning the drill bit slowly by hand. I have found that this dramatically extends the life expectancy of my drill bits.

- To anchor a minature co-ax cable to a PCB, use some thin brass strip about 6mm (1/4") wide to make a "ferrule and tab" to anchor the co-ax braid to the PCB ground-plane, giving an excellent electrical connection and a very rigid strain relief. The co-ax core can be soldered to a terminal pin. The brass strip is the sort used to make the contacts in battery holders, or it can be bought from model shops.

First prepare the co-ax cable as shown in the sketch.
Form a loop in the end of the brass strip by bending it around the end of a pair of long-nosed pliers.
Put the co-ax through the loop and crimp the loop onto the bare braid. Solder the braid to the brass. Cut off the brass strip, leaving a small tab to solder to the PCB. Tin the underside of the tab, then solder it to the PCB ground-plane.

This method works best for PTFE-insulated co-ax because the PTFE withstands the soldering better than polythene. PTFE co-ax is also more prone to the problems of strain relief due to the rigidity of the PTFE.

- Alternatively, for a fairly cheap connector for minature coax, I use 2-way Molex KK series or AMP MTA-100/CSA-100 connectors. These connectors use crimp terminals, but they can be sucessfully crimped with a pair of fine pliers as long as they are also soldered. Be careful to use a small quantity of solder, otherwise the contacts will not fit into the housing!

- To construct a custom enclosure without having to form sheet metal, get some aluminium angle from a DIY shop. It's sold in 2.5m lengths, about 12mm wide. Also get a big bag of small self-tapping screws. I built my enclosure using only an electric jigsaw (easier than a hacksaw) a file and an electric drill. I did get through about 70 screws, but any outer panel can be removed for repairs or modifications. To provide an effective RF screen, fixings should be less than 0.1 wavelengths apart. For HF this doesn't usually present a problem :o) Be careful if you wish to venture onto 70cm or above.

- When cutting sheet metal with an electric jigsaw, ALWAYS put a sheet of wood (ply, hardboard etc) under the metal and clamp the wood and metal firmly together. This is especially important when cutting large holes for displays close to the edge of front panels. Failure to use the wood results in a horribly-twisted panel!

- When wiring up boards in an enclosure, run the interconnecting wires such that any board can be unscrewed and turned upside-down without having to disconnect all the wiring. This makes fault-finding much easier.

Homebrewing - PCBs

- For designing PCBs I use the FREE Protel software available from here. It is an old DOS version, but it works well for relatively simple layouts. There are other demo/shareware packages available, but I like this one beacuse it's really free, simple to use, and runs on my humble 486 without complaining!

- For making PCBs I use Press-n-Peel film. This is great stuff (IMHO) and now available in the UK from Maplin. For some reason I've never seen it mentioned in any of the amateur radio mags or books but I can say it is the best method I have found, requiring nothing more than a laser printer or photocopier and household clothes iron. If only they could develop something to work with an inkjet printer... I came across P-n-P thanks to Bill Boucher, he has the best step-by-step instructions for using it and loads more useful stuff on his web site.

Homebrewing - PIC Micros

- The venerable PIC16F84, star of many a ham radio project, has now been improved on significantly by the 16F87x series. This family has more program memory, more RAM, more EEPROM, SPI, UART, more I/O, and still for less than 7 pounds in the UK. The datasheet is of course available from the Microchip website.

- Free programmers for the 16F87x are a bit thin on the ground, but Nigel Goodwin has been kind enough to put his on the web. Suitable hardware is available as a kit from Dontronics (and probably others) - it's one of David Tait's designs. The design uses the all-but-obsolete 74LS06/07 buffer, so I have designed a more modern version which has connections for in-circuit programming. Follow this link...

- An interesting PIC bootloader is available from Shane Tolmie's site. This small program and an RS-232 transceiver allow you to reprogram your PIC in-circuit via a high-speed serial port. For full details check out Shane's site. You still need a conventional programmer to get the bootloader into the PIC in the first place, though!

- If you haven't already come across it, the PIC Micro Webring is the place to go for a wealth of PIC-related information.


Last updated: 16 March 2002

Email me at gary.aylward@ntlworld.com

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