Archive for the ‘2. Ham Radio’ Category

Thoughts on CW (Morse code)

Sunday, December 16th, 2007

I have been a mostly CW (Morse code) operator on HF for the past few years. I have to admit something though – I have been using a Morse code decoding program for the computer. This has always bothered me – I should be able to copy by ear. After all, it isn’t good to be able to yell if you’re deaf.

So, I have nearly completely cut the use of the computer. I have slowed down to about 10wpm (I send at 13 and space it out a bit). My copying is still a little rough, but I am getting better.

This weekend I am away from the normal shack but I brought along my ts-2000 and my crappie pole. I have made a couple CW QSO’s – the right way. It really is pretty neat to be able to listen to the code and know what the other person is saying. Before, all I heard were a few things here and there – like some call signs, basic Q’s, abbreviations, names, states, and signal reports. I couldn’t listen to the code like someone was speaking to me. I am getting closer and closer to that point though.

I can send close to 40 words-per-minute when I am in my “groove”. My goal is to get my copy speed up to 20-25wpm. I used to send at 20-25 when I was in normal QSO’s – the pace seems to be about right. I can think and transfer my thoughts to my paddle pretty efficiently at that speed. It’s too bad I can’t go the other way around right now.

I am also a bit embarrassed to be an Extra and not be good at copying CW. That’s how it used to be and I think that’s how it SHOULD be. Therefore, I am staying away from the extra CW portions until I get my copy speed up. I don’t want to slow things down in the bottom 25. I also don’t want to throw in the computer again because that doesn’t make me a “true” CW operator, I’m only a CW transmitter hehehe. Since I am an Extra I need to operate like an Extra. I passed my 5wpm test 6 or so years ago, and I could pass it very easily now. I could probably pass the 13wpm test, but that still isn’t up to the 20 that an Extra was.

I am proud to be a Ham radio operator. Just because the FCC lowered the speed and then dropped the Morse code requirement all together doesn’t mean I am going to take advantage of that.

To quote the ARRL (from the cover of “Your Introduction to Morse Code”):

“Accept the Challenge, Enjoy the Reward”.

Where is the challenge now?

Homebrew/Kit Links

Friday, November 9th, 2007

http://www.ad5x.com/
http://www.qrpkits.com/
http://www.ohr.com/
http://www.dit-dididit-dit.com/
http://www.norcalqrp.com/
http://kd1jv.qrpradio.com/
http://www.elecraft.com/
http://www.dxzone.com/cgi-bin/dir/jump2.cgi?ID=8386
http://www.hfprojectsyahoo.com/ K5OOR

QRP, QRPp

Tuesday, October 30th, 2007

In Ham radio we have a term called QRP. This stems from the Morse code abbreviation for “reduce power”, or QRP? – “Shall I reduce power?”

Basically – it means to operate low power! Anything under 5 watts PEP CW is considered QRP. Less than 10 watts PEP SSB is also considered QRP.

Can you guess what QRPp means? Well, if you guessed, since the last p is lower-case, that it means even lower power, that’s correct! In fact, it means less than ONE (1) single watt! These power levels are measured in Milliwatts.

I have operated with QRP and QRPp levels before. I used to operate a lot of QRP at 5 watts. However, I figured out how to drop the power level down on my TS-2000 radio to QRPp levels. You do this by reducing the carrier level while the power level is set to 5 watts. You can also do it by adjusting the power level drive for 5 watts in the adjustment menu (you need the calibration software to do it).

I have routinely made QSO’s running 250mw of power before. The furthest one is to Big Sandy, TX. That was a LOT of fun. I even ran through a tuner to a non-resonant dipole (I guess it wouldn’t be called a dipole anymore, right?) on 40 meters (my QRP band of choice).

I measured my power output with the power level at 5 watts and the carrier level to 1 at 50 milliwatts! That’s 1/20th of a watt! Does this actually lend itself to QSO’s? YEP!

I just completed a QSO with W3TS in Halifax, PA running 50mw to a 40m attic dipole on 7.040 CW. Not bad! It is a little less than 300 miles between us. That’s not bad at all – most hand held radios run 500mw or 1w at the lowest power output and can hardly transmit a couple miles. I made it over 200 on 50mw!!

When I’m talking power levels there is another term that comes to mind – decibels, or db. The receiver Signal, or S, meters on our radios read in units from 1-9, then +10, 20, 30, 40, 50, 60dB.

How power level, dB, and S-meter readings relate is this: for every quadruple in power you “gain” 1 S-unit (1-9) of signal strength at the receiving end – all things being equal (antenna efficiency, transmission line loss, propagation, etc).

Example: if a person running 100 watts to a dipole on 40 meters has a solid S-9 signal talking to a station in another state, or beyond, (a reasonable amount) then he can cut his power to 25 watts and still maintain an S-8 signal strength. Now, a signal strength of S-4 (depending on band conditions, sometimes higher sometimes lower) is still PLENTY readable. The transmitting station could, theoretically, drop the transmitter power level down to just 100 milliwatts (1/10th of a SINGLE watt) and still be heard.

Does that make sense? So, why do a lot of Hams run amplifiers if the FCC requires “the minimum power necessary to maintain reliable communications”? It doesn’t make sense. That said, sometimes amplifiers ARE required to have reliable communications – but you shouldn’t run one ALL the time. It just wastes electromagnetic spectrum and makes it so others can’t enjoy the bands as much.

VHF Propagation

Saturday, September 22nd, 2007

This is an area that fascinates me. Most Ham radio operators think of Ionospheric Skip and Skywave propagation as phenomena that happen on the shortwave, or HF, bands. This happens because the Sun’s energy charges up particles (ions) in the atmosphere. The specific region is the F layer (and more specifically it is 2 layers F1 and F2 during the day). The area that is charged up is called the Ionosphere. Depending on the intensity of the charge, the frequency that is able to be reflected back to Earth changes. The more the charge the higher the frequency that can be bent back.

So, why am I talking about Ionospheric Skip while I am trying to talk about VHF propagation? Don’t all VHF signals break through the atmosphere? Even some HF frequencies break through the atmosphere, so why would there be any reason for VHF, even higher frequencies, to be bent back to Earth?

VHF signals can in fact be bent back to Earth! It doesn’t happen nearly as often, or can be predicted nearly as easily, as is done on the HF bands, however.

Some types of propagation that allow VHF signals to come back to Earth are: E-skip, Field Alligned Irregularities (FAI), Aurora, Meteor Scatter, Earth-Moon-Earth (EME), and Transequatorial.

Ill start off with the simple one – E-skip. This is by far the easiest phenomena to take advantage of. This happens most often because of temperature inversions. A temperature inversion is where warm air is above cold air. Its that simple. Typically, as you get higher in altitude the temperature falls. We all know that heat rises, but what creates heat on Earth? The number 1 source is the Sun. The radiation from the sun doesn’t heat up the air at all becaus there is nothing for the energy to run in to that will become energized. The Sun’s energy must reach the Earth before creating heat. The energy hits the ground and energizes it, creating heat. As this heat rises the Sun’s energy, passing right through, still can not heat it up. There is nothing in the air for the energy to hit. Therefore, as heat rises it cools down. The heat looses its energy because there is no energy to keep it going. What creates the temperature inversion, most often, is when a cold front (colder air is more dense and has more power over warm air) is pushing across the land. The higher pressure and higher density of the cold air moving acts like a shovel and scoops up the warmer air near the surface. The warm air gets pushed up above the colder air for it to loose its energy and cool off.

So, what does warm air have to do with radio waves? Warm air carries more water vapor.

Antenna Tuners? Transmitted signal efficiency

Saturday, September 22nd, 2007

This is a topic I just had to start up. I am a purist when it comes to Ham radio. Efficiency is what I worry about. I know I can’t get the ideal circumstances all the time and have to deal with poor efficiency some times. However, antenna tuners bother the heck out of me.

What is an “antenna tuner”?
Well, most people take the name literally and think it is something that tunes your antenna. Wrong.

An antenna tuner is not an “antenna tuner”. In Ham radio, all (or very close to all) of our radio systems have an impedance of 50 ohms. Antennas must present a 50 ohm load (or very close to that) to properly work. Now, that’s not to say a dummy load will work well as an antenna – it doesn’t. Hence the name “dummy” load. It presents a 50 ohm impedance to the radio to make it happy so it puts out full power, the “dummy” part means it doesn’t radiate (or very little) so it is safe to use as a test device for transmitting and not sending out signals on the airwaves. So, then to get a 50 ohm match at the radio through an antenna system that does NOT show a 50 ohm match we can do a little black magic – IE, use an antenna “tuner”. An “Antenna Tuner” changes the impedance of the transmission line or antenna (if a long wire) to 50 ohms before the radio. This makes the radio happy and able to transmit without worry into a good match. HOWEVER… and its a BIG HOWEVER – the match AFTER THE TUNER is STILL BAD!!! You did not change the impedance of the system, you just MADE THE RADIO HAPPY! Keep reading.

So, for an antenna to work well it must present close to a 50 ohm load to the radio. As the impedance changes so does your SWR (or Standing Wave Ratio). The higher the SWR the lower the power your transmitter will put out (in modern, solid state rigs) because the SWR-protection in the rig kicks in and drops the power so you don’t blow your finals.

Lots of times, Hams use wire antennas. Long wires, dipoles, doublettes, windoms, G5RV’s, etc. Hams in a pinch sometimes use one antenna on all bands. Well, this is where we get in to the efficiency issues. To get the most out of your antenna you need to have the antenna resonant on the frequency of operation and you need it to present a 50 ohm match to the transmission line (coaxial cable from rig to antenna) so the radio is happy. When you load up an antenna on bands it was not designed for you get impedance mismatches.

If you do not present a 50 ohm match, or close to it, to a 50 ohm impedance transmission line you LOOSE power (both RX and TX) out of the transmission line. Coax loss is rated in dB (decibels) per 100′ per frequency of operation AT NOMINAL IMPEDANCE (50 ohms). Power, in dB, goes like this – every double in power is 3dB. If you show 50 watts to a 3dB loss system you get 25 watts out, likewise 500 out with 1000 in.

As the frequency increases, so does the loss. At HF we really don’t need to worry about the loss THAT much. That is.. until we show poor impedance to the line. A poor impedance drastically increases the loss in the line.

SWR, or Standing Wave Ratio, is a measure of reflected power v.s. input power. SWR works like this – any double in impedance is an SWR of 2:1 (2 times nominal). At the same time, any half impedance is ALSO a 2:1 SWR (nominal/2). For example: an impedance, in a 50 ohm nominal impedance coaxial feed line, of 100 ohms gives an SWR of 2:1. An impedance of 25 ohms to the same feed line also gives an SWR of 2:1.

A 2:1 SWR is the maximum that is typically accepted by modern radios. Even then, the SWR protection has already kicked in and dropped your power. Youll be lucky to get 60-70 watts out of your 100 watt radio with a 2:1 SWR.

Back to the cable itself now. Lets say the cable we are using is rated at 1.3dB/100′ loss @ 30MHz (LMR-240, a typical cable of the RG-8x size used by the majority of us). Lets also say we are running on 10 meters (30MHz is the high point of 10 meters), it is 100′ long, and we are presenting a 2:1 SWR to it. I haven’t done the exact calculation here (there are more variables involved with calculating this than just SWR and loss) but lets say that the loss increases to right around 3dB. That doesn’t seem too unreasonable, given our initial loss of 1.3dB/100′.

Now, remember – a 3dB loss is equal to 1/2 you input power. If you get 50% of your power through the transmission line then that means, with that 60-70 watts in (after SWR protection in the rig), your antenna is only seeing 30-35 watts out. Now, add in the efficiency of the antenna you have up. If you have a beam antenna or an antenna with some gain, then you can ADD power back in (gain means more of the radiated energy is concentrated in a certain direction). If you’re like most of us and running a 1/4w vertical or a dipole, then, unless it is optimized (and at a 2:1 SWR it isnt) you are LOOSING even more. 30-35 watts (most likely less than that) out of your 100 watt radio is probably not what you want, is it?

Now, I am going to bring in a whole other issue. Not only are you loosing efficiency (power, rx signal strength) through a bad match in coax you are ALSO generating interference, or RFI. Your signal loss through the cable when you transmit has to go somewhere. It is dissipated as heat, some of it radiates (IE, your coax is part of the antenna), and SOME of it is distorted and radiates as RFI trash. The higher the voltage at the feed point of the antenna and the worse the impedance match the more RFI you generate.

A dipole for 80 meters is roughly 134′. If you look at a graph of the voltage/current distribution on a dipole at its resonant frequency you have high current and low voltage present at the feed point. Voltage is opposite of current. Now, a dipole is 1/2wl – a “classic” dipole anyway. Lets use this antenna on 40 meters. 40 meters is half of 80 meters, which means the frequency is half as big. That means our 1/2wl antenna on 80 is now 1 full wl on 40, 1/2wl each leg. Now we need to change the graph of our current/voltage distribution. The voltage is still high and current low at the ends. However, the feed point of the antenna ALSO now shows high voltage/low current. In fact, the voltage is as high as it could possibly be at the feed point.

As I said before, the higher the voltage the more RFI generated. Higher voltage can also arc across longer distances. The capacitors in your manual tuner have plates that are close together. The higher the voltage through these capacitors the easier it is to arc across the plates. Arcing causes RFI and also severe damage to the capacitors. Every arc/spark of any voltage emits RF. The higher the voltage the more RF, and the more damage done – the more melting power the arc has. Unless you are building a spark-gap transmitter, arcs are BAD.

Through all of this I am explaining a desk-top, manual, in-shack, type antenna tuner mounted close to the radio with coaxial transmission line. There are ways to get around these poor impedances and losses, however! Keep reading.

Antenna tuners need not be close to the radio. They are convenient to have close to the radio so you can crank the knobs or push the buttons. However, if you can change the impedance of the antenna system to 50 ohms then why not mount the tuner close to the ANTENNA instead? This would give you a PERFECT 50 ohm, flat 1:1 SWR, impedance through the entire length of transmission line. This would minimize losses to the least possible. The only losses you have now are the tuner losses and the antenna losses (given its not optimized).

The only solution that makes sense here is an automatic tuner. SGC makes some good ones. The Icom AH-4 is popular, although poor matching range. Also, LDG makes a remote tuner, or you can modify a Z100 or similar for remote use. If you are operating on the low bands and want a tuner that can be remotely operated to tune the entirety of one band (160 for example) then you can make a loading coil with a lead-screw drive that will compress and expand the coil to adjust the impedance. Its pretty rough, but if you can build one for $30 youll save much more on the cost of an auto tuner.

Using a tuner on an antenna that is not optimized for the frequency of operation is not ALL that bad. In reality, all the power you are capable of sending to the antenna is getting to it. Gooch’s paradox: “RF gotta go somewhere”. If you get your RF to the antenna it will radiate. Its that simple. The performance of the antenna (gain, pattern, etc) might be an issue… but it will radiate.

Another way of getting around the impedance problem with a tuner is to use balanced transmission line instead of coaxial cable. For this you need a balun. Most manual tuners with a balun have a 4:1 balun. However, it might be beneficial to use a 1:1 instead. If you have a long antenna and tune it up on a high band you have a low impedance. For this example Ill use 40 ohms. If you use a 4:1 ballun at the tuner the impedance the tuner actually sees is now 10 ohms (40/4=10). 10 ohms is harder, MUCH harder, to match than 40 ohms is. In fact, 40 ohms wouldn’t even need a tuner.

The problem with balanced line is how you route it. It can not be close to anything conductive, or relatively conductive. That includes tree branches and leaves (the water, sugars, saps all have some conductivity and will throw off the balance of the line). Maintain at least several inches (the more the better) of space between the line and anything else. This causes problems getting the line in to the shack. Going through a window with a spacer to hold the line at a good distance from the frame is a good idea. Going through a wall is OK as long as the line isn’t close to anything metal in the wall (nails in studs, wires, ect).

Balanced line, when used properly, is the BEST transmission line to use. 450 ohm is the most common, others include 300 and 600 (true “ladder line”). I’m sure there are other values as well.

Remember, an “antenna tuner” doesn’t actually tune your antenna. It merely is an impedance matcher so that your radio sees a 50 ohm impedance. There are many other factors you must consider in order to have an efficient, RFI-free system.

If “antenna tuners” hurt your efficiency and just aren’t that great to use, then why do I have one? There are lots of situations when tuners are great to have. They are a must if you want to use a dipole and cover an entire band (edge to edge). Ill use 40 meters for example. You can get a 2:1 SWR width of one section or the other – SSB from 7.150-7.300 and CW/digital from 7.000 to 7.150. but to cover a whole band a tuner is the only way to do it. To minimize losses in both ends you tune the antenna to 7.150, right in the middle, and use the tuner to get the edges. Or, if you operate CW more then tune the antenna for CW and use the tuner for SSB, or the other way around. Longwire antennas need a tuner. A longwire can be used on any band, given it is 1/4wl at the lowest frequency you intend to operate on (the longer the better). Without a tuner, a longwire would be useless. Balanced line antennas (doubletts for example – a random length “T” antenna fed with ladder line – NOT a dipole) need a tuner unless the antenna is optimized for one frequency. Basically, any antenna that is not resonant at any specific frequency needs a tuner.

Even I use non-resonant antennas. We all have to at some point. If I had my own place with 50 acres to put up radio towers and antennas then maybe I wouldn’t need a tuner. Until then, I need to use compromise antennas. I understand how my antenna systems work and I must accept the efficiency I can get. However, I CAN make my systems as efficient as I possibly can (short coax, balanced line instead of coax, close impedance, etc). The name of the game is to minimize losses. That’s all.

Amateur Radio Activities – What is it? Hows it Work?

Saturday, September 22nd, 2007

Amateur Radio: What is it?

The Federal Communications Commission (F.C.C.) defines the Amateur Radio service as: “A radiocommunication service for the purpose of self training, intercommunication, and technical investigations carried out by amateurs, that is, duly othorized persons interested in radio technique soley with a personal aim and without a pecuniary interest”. Part 97.1(4)

So, what the heck does that mean? Well, Amateur Radio, as a service, is all volunteers. We provide our skills and equipment for use in public service, emergencies, and when any backup communication is needed by any other service. We can provide communications for such events as marathons, bike races, football games, search and rescue missions. We can relieve strain on current communications systems already in use, as well as bring up systems where there aren’t any or they have been rendered useless due to a catastrophic event. Two prime examples are the aftermath of Hurricane Katrina and the Wold Trade Center tragedy. Amateur radio played a vital role in linking emergency operations, hospitals, law enforcement, and public agencies. Amateur radio got through when current systems were down or over-crowded. The National Weather service also utilizes Amateur radio operators to get vital weather reports from on the ground – severe weather that is currently happening (tornadoes, large hail, strong winds) as well as report damage after a weather event.

OK, enough of the “practical” stuff.. lets cut to the FUN!

Amateur radio operators can talk to people anywhere – across town, across the state, across the country, even around the world. Yep, I just said around the country and around the world. Well, in actuality we can communicate OUTSIDE of this world. The Space Shuttle has a VHF Amateur radio station on board and most astronauts are licensed operators. We can also use a variety of satellites orbiting the Earth to communicate to one another. You know the big, round, white ball in the night sky? Yeah, the Moon. We can use that too! EME , or “Earth-Moon-Earth”, is the ultimate long-distance, weak signal mode of communications. You can literally bounce your radio signals off of the Moon. Pretty cool, huh?

Another activity is Amateur Television. This is sending live video and audio across the radio waves to other stations. This is similar to watching TV, only it is two-way. Amateur television systems can be used at home, in your car, remote monitoring sites, and even on remote controlled devices. Yep, you can put an Amateur Television system in a radio controlled airplane and fly it like you do playing a computer game. You can make your radio controlled car drive all around the house chasing your dog and not be in the same room.

Talking to other people on the radio waves is where 90% of all amateur radio operation takes place. We do this in a variety of ways. We can pick up a microphone and talk, this is called “phone” (SSB, AM, FM, Digital Voice). We can send Morse code with a “key”. Yep, Morse code is still used – its one of the BEST modes for cutting through weak signal and/or poor band conditions. Computers have been used in Amateur radio for many years now. We can type to other people over the radio as well as send and receive pictures and data.

DX’ing is a term we use for contacting people all over the world. Every country has it’s own unique letters and numbers in operators’ call signs. In the U.S., the prefixes can be one or two letters beginning with W, N, A, or K followed by any number 0-9 (there are 10 call districts). In Mexico the prefix begins with one or two letters beginning with X and has any number 0-9 following. The islands of Curacao and Bonaire begin with PJ2, PJ4, and PJ9. Every country/island/entity on the planet has its own designators.

QSL cards are exchanged between operators who wish to confirm their contacts. It’s one thing to write the information about the contact in a log, but you have to officially confirm that contact with a QSL card to show proof of that contact. These QSL cards can be used towards many different awards – Worked All States, DXCC (worked 100 or more DX entities), Worked All Continents, etc. Many operators like to display these as “wall paper” in their stations for visitors to look at.


Some of my “wallpaper” at my previous location. The left 3 are from Meteor Scatter contacts on the 2-meter band, the big cluster to the right (and they go lots further down) is my collection of cards from Top Band – 160-meters. I was working on the Worked All States award – Top Band only, all Morse code (separate endorsements). I got 30-some in a couple years of being on the band, the latter year being the most serious I was ever in to it.

Amateur radio is the ultimate “nerd” hobby. You can think and analyze Amateur radio for an eternity and never feel like you have done it all. You can get as deep in to it as you want or as shallow as you want.

To get a little deeper into the subject – Amateur radio is “radio communications”. We send out signals in electromagnetic energy to other radio operators – as close as a couple feet to as far as you can imagine, and then some.

How do radio signals get from one place to another? Well, we call this “propagation”. Throw a rock in a calm pond. See the ripples spreading out from where the rock went in to the water? These are waves. The same principle applies to radio waves, only you can’t see them, you can’t hear them, and you can’t feel them. They are all around us. They go everywhere. They come from just about everywhere. We, as radio operators, can make use of this propagation to
communicate.

There are a couple modes of propagation that are important, for starters.

1. Line of Sight
This is the propagation of radio waves in a straight line from one point to another. As long as the two antennas on the stations in communication can “see” each other (not literally) you can get a signal through. The density and material, as well as the distance between the station and radiated power all affect the strength of the signal at the other end. The higher the antennas of the stations communicating the further apart they can be. That is why cell towers are tall and antennas are mounted on tall buildings. This mode of propagation works best on frequencies in the VHF spectrum and above. However, the Shortwave bands also operate line of sight for
a little bit.

2. Sky Wave, or, for the geeks – Ionospheric Skip This is what makes the Shortwave bands (all those below 30mHz) work so well. These are the waves that can go all over the world. There are many things that affect how these waves propagate. The main factor is the ionization in the atmosphere. Basically, the sun charges up particles in the atmosphere (the F layers to be specific) and the radio waves bounce off this ionization. The take off angle of the signal, or the angle at which the signal propagates from the antenna, also affects how Sky Wave propagation works. The lower the angle (the closer to the horizon) the shallower the skip angle is of the atmosphere. The shallower the skip angle and the softer the reflection the further the radio signals go. The frequency of operation determines how soft the angle of reflection is. The higher the frequency the softer the reflection, the lower the frequency the harder the reflection. The frequency at which the signals no longer are reflected, but instead break through the atmosphere, is called the Maximum Usable Frequency. Depending on what this value is, the skip zone between the reflections changes. With the HF bands we can pretty much pick a frequency for wherever we are trying to get to. Now, I say that loosely. We try to contact different general areas – such as Africa, Europe, Australia,etc. The signals don’t go to one specific town. If you are operating an emergency or public service station and have a need to communicate with a specific station you can choose a specific frequency band to talk to where you need to talk to. Typically, if you are communicating within about 500-800 miles 40 meters is a good band. Further than that and 20 meters is preferable. However, with the current condition of the solar cycle these bands have degraded performance.

To make propagation easier to think about Ill use this analogy: a radio signal is like light. A regular light bulb, open, with no shield/cone (for directivity, like a headlight on a car), spreads light out equally well in all directions. Place it in the center of a room and it illuminates the whole thing well. The light emitting from the bulb is going to everywhere in the room by line of sight. The light “sees” everything. Now, put a big mirror on the ceiling near the doorway and in-line with the light bulb. Now look down the hall. See the patch of light? That is sky wave propagation. The light is reflecting off of the mirror on the ceiling to the floor of the hall, some several feet away.

If you have any interest in radio communications, Amateur radio is the ULTIMATE!!! Even though it is called “Amateur” the skill and usefulness are anything but “Amateur”. You can get as deep in to the subject as you wish. I can guarantee one thing – you will learn a lot with radios!