Build This Simple SMT Station

Dinner and a movie? How about pizza and a project?
SMT parts are rapidly becoming the "norm'' in consumer electronics manufacturing. This “home-brew” device can make the learning and building process with SMT devices a more pleasurable event.

My initial entry into the hobby was during the generation of tube-type gear (and yes. I'm older than many and younger than a few). I then went to solid state and now have progressed to SMT (surface mount technology) devices. Not wanting to be “left behind,” I ve been thinking of trying a project using SMT.



SMT. as ii s called, is becoming more and more the standard of the industry. That's not to say that all parts are being replaced by these miniature devices, but it sure seems to me that there are many more projects designed around them now than in the past. The manufacturers of consumer electronics can produce these parts more economically than “through-hole" items. Then there’s the placement of parts on an assembly line, where robotics can handle the task effectively using the newer devices. Lately, most of the consumer products I’ve obtained were constructed Using this technology. The “writine is on the wall," or should I say. the “chips are on the board."

Reverse Breakdown Voltage

Measurement Adapter

The circuit shown in Fig. 1 is the schematic for a Reverse Breakdown Voltage Measure-ment Adapter. Many times it is necessary to determine the breakdown voltage of a semiconductor. A reverse-biased P-N junction conducts current when its reverse breakdown voltage is exceeded. For a regular diode, this is the same as the peak inverse voltage (P1V).

Bipolar junction transistor reverse breakdown voltages can also be measured with this device. Furthermore, a zener diode’s breakdown voltage can be measured. If the current through the device under test (DUT) is limited during reverse bias, the junction voltage drop remains relatively constant.



This design will test zener diodes from 5.1 V to 75 V. A multimeter set on DC volts is plugged into the unit along with the DUT
Reverse breakdown voltage is read directly from the meter. When testing reverse bias diodes, a display of 5.1 V denotes a 5.1 V zener diode. Similarly, a display of 75 V represents a 75 V ze-ner diode. When measuring these voltages, remember that the diodes usually have a ± 5% or ± 10% tolerance.

The zener diode voltage is dependent on the current through the device. The reverse breakdown voltage measurement adapter described here has a short-circuit test current of approximately
10 mA. If the rated operating current of the zener is greater than 10 mA, the measured zener voltage will be incorrect.

Coronal Holes

Solar activity is also likely to decrease during the tatter half of the month, improving the propagation oultook even fur ther. However, there are five trouble spots to watch out for, as indicated by the l+Fair-to-Poor' {F-P) and "Poor' (P) days marked on the calendar, The 19th-2 ] st looks particularly troublesome with moderate to strong llares or other events likely.



You may have noticed a lack of clearly "Goud" (G ) days in my forecasts over the Iasi year. One reason for this has been the high incidence of another solar phenomenon — coronal holes. Coronal holes arc large regions — much larger than sunspots — that are cooler and less dense than the surrounding atmosphere, or corona. They are usually located over the polar regions of the sun, hut during solar maximum the\ may appear anywhere on the solar disc. When this happens we often see a marked increase in the solar flux and more frequent geomagnetic disturbances.

Emergency HF Operations

Although this column focuses on three different areas, mobile portable, anti emergency communications — to a greai degree they tend to intertwine. The ability to provide communications to support a community effort, whether it is a routine event like a parade or “fun run." or a disaster, requires that we set up communications in a manner that supports the event In some eases, this means that some or all of the radio operators w ill be al the scene, and if so, the ability to ^et up a station in an unexpected location on short notice w ill be critical. We tend to assume that the focus will he on short range communications, and this can often he quickly and easily done hy use of UF and VHP equipment.



However, amateur radio may no longer he the primary method to provide short range communications during a disaster Public service radios are becoming more flexible Lind even the ceil svstem has made major advances. It is safe to assume that eventually these systems will increase in reliability to the point where the> will continue to operate to full expectation eve 11 under the worst of conditions. What will amateur radio s role he when that happens? II we are going to continue to be an important asset, we need to he able to provide other appropriate services.

Converting Surplus: A1296 MHz 5 Watt Amplifier

This time, ihe focus is on converting a higher power module ihai is capable of a minimum of 5 walls output and am tv pushed tohightToutputpowerk^ekThennssomc similarity between the surplus modules and commercial modules that aiv available for this same frequency band that do not require modification* Existing modules are ihe older Mitsubishi M57762* see Photo the newer Mitsubishi M6T715 \ 296 МН/ f> aver amplifier 5 waft class mochdes. Hie Mitsubishi nxxlufes air constructed in black epoxy aixl cannot the modified as they are completely sealed, unlike ihe Fujitsu surplus module Flhe) run from volts directly and do ixn require minus bias supplies.



Comparing the Mitsubishi modules and the Fujitsu module they are quite similar except that the fujitsu module has a removable metal coven It can be gently lifted off lu expose the circuitry of the amplifier PC board, allowing modification to the internal circuitry to make it useful ai 1296 МН/. Modification details are shown in Photo A. The Mitsubishi modules are sealed in a black plastic epoxy case with two heat sink tins on eilher side and five connection leads protruding from ihe module case. No hint of circuitry is apparent in ihe black modules. The cost of the Mitsubishi modules is a little expensive, slightlj overS60 last time I checked. A fine module hut costly.

Now Hear This!

Home-brew yourself a magnetic headphone.



In the past few years, there has been ал increased interest in the early days of radio. Periodically you will see articles published on the construction of crystal or regenerative radios. There was even a crystal radio building contest in 2001. 1 entered the contest, learned a lot and had a blast even though my project did not win. 1 attempted to make all of the parts for that radio. This is part of that project
With readily available items from your junk box or hard ware store, it is possible to fabricate a functional magnetic headphone that is sensitive enough for crystal (diode) radio operation. This headphone has been used with in у crystal radio and performs well: the best part is that it is homemade. If you don't have the exact parts, experiment with what you have, and most of all. have fun: in the process you will learn something that will be useful. The materials and tools used in this project
can be dangerous, so be safe in your work environment and use e\e and ear protection.

This Thing Called Wire-Wrap

Righi from the start, you must breadboard a prototype of the "want to be" new circuit to check the function and the expected performance. We folk* w ith an engineering background know that a computer simulation is not less expensive, easier to use, and so on. Using the “freehand” design utilizing mullisourced components requires a bread board to check the function. Expensive software packages, etc.. just do not lend themselves to the ham radio community verv well.



I have found over the years that a good breadboard system such as shown in Photo В is very helpful. Pushing components into the grid svs-tem performs some of the interconnects. Tlic rest of the connections are made with #22 solid wire jumpers.

On his is an inexpensive and effective system of breadboarding. The system is reusable many limes over. You breadboard only small parts of the overall design just to verify the circuit function.

Now any antenna performs is a very important characteristic, without which there would be no wireless communications. However, if we can set aside an antenna’s
performance ability for a moment and give consideration to a couple of Other important characteristics, the question stands a better chance of being answered
correctly. All too often the individual asking the question has not given thought about two other very important considerations for portable use; the intended
“use" for the antenna and a familiarity with what’s “available.” Once the user understands and becomes familiar with these two issues,
then performance can be given its deserving consideration as a determinate in deciding which antenna is best.




I have been told that religion, sex, and antenna “stuff” can be taboo discussion items. However, after having heard so many QRP hams ask this very question
regarding best antenna selection, I feelthe need to run the risk of being involved in such a taboo discussion. Note that I don’t plan to include cost and
ultimately “real value’* into this discussion. The variables involved with real value are so numerous that this would be an article all its own!

Twin for Two
Thai's what I thought, until 1 realized that doubling the capture area wilh two full-wave loops ted simultaneously is even better. Several years ago. I replaced my 2-meter J-pole with a 2-element quad, and I was very pleased with the performance of ill is antenna upgrade. Now that I have replaced the 2-element quad with the twin loop antenna. 1 am even more pleased. Scratchy signals from outlying areas are now registering 3/4 scale on the S-meter, Now I
can hear everybody on the local 2-meler simplex nei and get a good signal back to them with 5 watts. I chose to make this antenna from 1/2-inch copper tubing because of tis good conductivity and large surface area.



Here is a 2m antenna I constructed from info that I got from VV7YP of western Wyoming. Of course. I changed it all around to suit my purposes, hut the idea is the same.

Twisted Tale: The Dial File

Have you considered the use, application, and design of “dials" as used on radio equipment from the very early days? When you stop to think about it. dials are the communication interface between humans and electronic devices. Dial markings and numbered reference points provide feedback to the operator of how the equipment is set up and/ or adjusted.



Because of the importance of dials to ham radio and many other forms of electronic equipment. I'd like to take you on a journey of “dials” as they’ve
been used over the many generations of radio as we know it today. I’ve managed to collect a few pictures of dials dating back to 191Because of the numerous dial designs and iterations. I've collected only a few that are rep-reseniative of the many types that have been developed.

2 m/70 cm Quad Revisited

This new design using 3/4-inch PVC water pipe shows a little bii belter performance and is much lighter in ueiiiht. In [in', version, I used AWG-12 bare copper wire fed througli 1/4-inch agricultural PVA tubing. This looks better and the performance is better on 440 МН/. My use of a ferrite choke also enhanced the performance considerably: about 13 dBd over a dipole for under $20 (U.S.). The boom length is about 4 in 5 ft., and an old TV rotor docs the rotating.



Take a look at Fig. 1 for ihe basic dimensions and layout of this PVC wonder. This modern-day “Plumber’s Delight" is perfect for the 2 m/70 cm bands and in particular for work. The system radiates both two-meter and 70-centimeter frequencies on the same elements with a boom length of under four feet (114 cm). The measured gain figures arc about 11 dB over a dipole on iwo meters and 13 dB over a dipole on 70 cm. The additional gain on 70 cm is due to the three wavelength elements.

YOU Can Build This VLF to HF

Loop Receiving Antenna
This is the product of an intentional trade-off; I wanted a mechanically simple loop that could be constructed from inexpensive plumbing fixtures and that used standard enameled magnet wire. There are two main drawbacks to my construction technique, both of which arc related to bunching the turns:

• The loops have a lot of distributed capacitance, which reduces the maximum frequency.



• The standard inductance formulas produce inaccurate results, so some cut-and-try will be necessary if you deviate from how 1 built my loops.

The Quickchanger

This makes mixed-mode/band operation a breeze.

When i was bitten by the packet bug, I bought an AEA PK-64 TNC to use with my С*64 computer. Soon I discovered that, in order to switch from HF to VHF, 1 had to plug and unplug radios, mikes, and wires. A real hassle!



Time and Labor Saver

To solve the problem, I designed and built the Quickchanger, an in-teface box that lets you switch a single mike, a TNC, a phone
patch, and two speakers, all to either HF, VHF, or off. This is done with the row of six three-position DPDT toggles on its front panel.

Improve your TNC’s DCD circuit

Make your DCD faster and more discriminating.

Proper data carrier detection (DCD) is one of ihe most impor-tanl items lo consider on any multiple access packet channel. The DCD circuitry for nearly all currently available TNCs are deficient for use on a radio channel, Some are better than others, but most can be dramatically improved. This article shows you how to do just that!



Purpose of DCD

The DCD's main function in the TNC modem is to prevent transmission on an occupied channel, If two stations transmit at the same time a collision occurs, which corrupts the data, which means both stations have to re-send the data. This increases the total load on the channel and reduces throughout Гог everyone.

What's the optimum DCD circuit for packet radio? It should have these five key features; It must reliably distinguish information from noise: it must transmit packet data uninhibited by an open squelch; its signal should remain valid through momentary fades or collisions: it should tolerate signal level differences: and it must be fast.

GRAPES 56 Kb Modem

We’ve come a long way from 1200 baud packet.

How would you like to be able to send the equivalent of a standard 5.25,r IBM PC floppy disk (360 Kbytes) by packet radioin less than two minutes? How about transmitting telephone-quality digital voice over the air? Sound too good or expensive lo be true? Not at all! It's being done right nowh with equipment and software available to any interested amateur.



The key is the 56 Kb/s modem designed by Dale Heatherington WA4DSY and distributed by the Georgia Radio Amateur Packet Enthusiasts Society (GRAPES). Since its unveiling at Dayton in 1987, this modem has progressed through the experimental and beta lest stages and is now in routine production and use.