Great Circle Map Generator

For those of you who are interested in radio listening, particularly over long distances (AKA DXing) with even a moderately directional antenna, having a great circle map projection for your location is a necessity.  Looking at a Mercator Projection, the normal “flat” map most are familiar with, one might come to the conclusion that due west from upstate NY lies the Washington/Oregon state border.  Appearances can be deceptive, bearing away at 270 degrees true (due west) from upstate NY is the California/Mexico border.

This is because we live in a big sphere.  In this regard, the only place the Mercator Projection is accurate is around the equator unless one is going due north (0 degrees) or due south (180 degrees).  The further north or south from the equator, the less accurate a flat map is.   Therefore, having a Great Circle map projection based on your location is handy for choosing the right azimuth to listen along.

As with many things, the internet provides the required tools to generate a great circle map for any location in the world.  The first thing needed is an accurate fix of your location.  This can be obtained via GPS, or, if you know how to look at a map and or satellite picture, itouchmap can be very useful.  Once you know where you are,  you can plug that information into this Great Circle Map Generator.

I saved the image as a bit map and used it as the wallpaper on my computer.  That way, I just need to minimize any running programs and I can see what the correct azimuth is to any place in the world.  This is for upstate NY:

great circle projection
Great Circle Projection

The first aid kit

One of the things that was drilled into my head when in the military was first aid, which we were all required to learn. Those of us who worked around high voltages were also required to know CPR, including passing the American Red Cross CPR course.  I have used CPR on three separate occasions, and none of the victims lived to tell about it.  I have been told by my wife’s cousin, who is an ER doctor, that that result is fairly typical, especially in older persons with heart conditions, which in two instances was the case.

I have always carried a standard first aid kit in my truck.  Things like band-aids, gauze pads, sterile water, Hydrogen Peroxide, medical tape, splints, antimicrobial cream, blankets, etc.  Nothing hugely complicated, something like this unit.  I have used it recently at accident scenes, which I tend to stop if it looks like they need help.

Philips Heartstart onsite AED
Philips Heartstart onsite AED

To complete this, I have also purchased an AED.  As one medic once said, if a heart gets shocked out of sinus rhythm, it can be easily shocked back into sinus rhythm provided it is done quickly.  Working on high-voltage power supplies always entails some risk, even when all safety procedures are followed.  As little as 60 mA can cause arrhythmia.  Dry skin has a resistance of about 300 ohms, which means that 180 VDC is the threshold for fatal shocks.  This value is much lower if the skin is wet. Any shock received through either hand is likely to travel through the chest and can effect the heart.  Many of the transmitter sites we service are remote, medical help may be 30-60 minutes away under good conditions.  Having an AED on hand is just a little bit of extra insurance, that will hopefully never have to be used.

CPR procedures have been updated in the last few years, if one has not recently reviewed them, it might be worthwhile to take a refresher course.  I will say, hands-only CPR is an improvement not only because it is more effective, but also because most heart attack victims vomit and lose control of their bowls.  Reduced contact with someone else’s stomach contents is always welcome.  This AED came with a training video CD.  While AEDs are designed to be intuitive, having training on their use is always a good idea.  The Red Cross also gives classes that include the use of an AED with hands-only CPR.

This is what you’ll get…

Back many, many years ago, in a city far away, I was driving down the road and I flipped one of “my” stations on the air.  The end of this song was playing:

The ending sounds an awful lot like a Moseley MRC-16 transmitter remote control’s return telemetry.  When I heard that on the air, my first response was “HOLY SH*T! The telemetry is on the main channel!”  A little voice in the back of my head said “That is not possible.  How is that possible?”  I grabbed the gigantic, then state-of-the-art Motorola bag phone and dialed the studio hotline, just before I hit the  “send” button, the song faded out and the announcer came on back selling “Karma Police by Radiohead

Wow.  Radiohead?  Karma Police?  WTF?

I almost had a coronary.  When I got home, I tried explaining this all to my then-girlfriend, who didn’t get it.  Few do.  At the time, making such an error would be very bad form indeed and likely open the unfortunate party to all sorts of snickering and finger-pointing at the next SBE meeting.

Working with Surface Mount Technology (SMT)

A quick glance at almost any circuit board these days will show that almost all of the components are surface-mounted.  They are small rectangles or squares that sit on top of the circuit board.  This is different from the through-hole components that were used for many years and are still found in older equipment.  There are radio engineers who feel that surface mount components are too hard to work on, thus the boards are not repairable.

California Amplifiers C band block down converter
California Amplifiers C band block down converter

As with anything in the engineering field, there needs to be a cost/benefit analysis.  Most computer component boards, things like NICs, modems, sound cards, VGA cards are very inexpensive, and often times it would be more expensive to repair the board than it would to buy a new one.  In other situations, however, local repair of circuit boards makes good sense and can be a good learning tool.

Consoles and transmitters offer some good opportunities for local repair, provided the schematics are available.  SMT component troubleshooting is the same as through-hole troubleshoots, except the components are smaller.  That is where a magnifying glass comes in handy.  I purchased a magnifying glass/light to work on SMT boards.

three diopter magnifying lamp
three diopter magnifying lamp

Soldering and unsoldering techniques are also different.  A temperature controlled soldering iron with a small tip is important.  I find the easiest way to unsolder a component is with solder wick.  Once most of the solder has been wicked up, a brief touch of the iron and the component will come off.  Small resistors and capacitors are fairly rugged, but should not be overheated.  Semiconductor components such as diodes, transistors and ICs are susceptible to heat damage and Electro Static Discharge (EDS).  A grounding wrist strap should always be used when handling semiconductor components.  Soldering iron temperature should be enough to quickly melt the solder and heat the connection surface without overheating the SMT component.  Lead free solder requires slightly higher temperatures than the traditional 60/40 rosin core.

Weller WD1 temperature controlled soldering station
Weller WD1 temperature-controlled soldering station

A temperature-controlled soldering station is a must.  Too much heat will damage components and boards, too little will make soldering SMT an arduous task.

Soldering supplies
Soldering supplies

Other soldering supplies include liquid flux, desoldering wick, flux remover and 55/40/5 solder.  The desoldering wick makes it easy to clean up an errant solder deposits and is the best way to desolder surface mount components.  I have had limited success using a solder pump on surface mount boards.  They do come in handy for RF MOSFETS, which have large tabs, often with liberal amounts of solder applied at the factory.

Soldering new components:

HF receiver preamp SMT board
HF receiver preamp SMT board

A typical 0.1 uf capacitor is placed on the surface mount board and ready to be soldered.  These components are all small, but I would characterize this as a medium sized one.  There are some very small diodes, ICs and other devices that require the magnifying glass to identify pins and polarity.

The best way that I have found to solder components onto a surface mount board is to use a little bit of liquid flux on the board.

Using tweezers or small needle nose pliers, place the component.

Soldering 0.1 uf bypass cap on SMT board
Soldering 0.1 uf bypass cap on SMT board

Wet the end of the soldering iron with a little bit of solder.

Using the placing tool, hold the component in place and touch one of the pads with the soldering iron.  This should tack the component in place. Solder the component to the other pad using the soldering iron and solder.  Then come back and touch up the tacked side.  I have found that 600 degrees F is a good temperature to quickly melt the solder, while not heating up the component too much.

HF receiver preamp with bypass capacitor soldered
HF receiver preamp with bypass capacitor soldered

Sorry I could not get pictures of the actually process, I don’t have enough hands to hold the soldering iron, hold the component down and take a picture.

HF preamp based on Norton 1N5109 design
HF preamp based on Norton 1N5109 design

The completed preamplifier.  I have been calling this an HF preamp, because that is its intended use.  In practice, this preamp should work well from 50 KHz up to about 75 MHz, with 3dB points at 30 KHz and 100 MHz.

Norton HF preamp schematic
Norton HF preamp Schematic 

The Norton design is an inverse feed back and using the 1N5109 transistor, which has input and output impedance of 50 ohms, makes it simple to implement.  In testing, I found this unit has about 10-11 dB of gain with about 4 dB of noise.   The use of SMT makes the design stable and I didn’t see any evidence of oscillations when testing it.  More on the preamp here.   I installed it out at the base of my K9AY antenna and it can be remotely turned on and off as needed.  My main reason for wanting it is to overcome the 6.5 dB signal loss in the four port hybrid receiver coupler and transmission line I use.  Truth be told, most of the time it is off.