Angle of Radiation – What is it?

Your signals are effected by the Angle of Radiation as they travel from your radio to the other side of the planet. This paper by K2WH explains why.

Angle of Radiation – What is it?

One of the more important performance characteristics of an antenna system is its angle of radiation. Angle of radiation is not built into an antenna, you the amateur make that happen by the placing your antenna at the proper height. Therefore, I thought of this mental exercise of what radiation angle really means.

Angle of radiation when referring to antennas, is simply the take off angle of the RF field when launched from your antenna in relation to the ground (earth). That is, if your dipole antenna is low to the ground (< 1/2 wavelength), in relation to its frequency of operation, the angle of radiation from the dipole will be at or close to 90 degrees – straight up and the dipole will behave as an omni-directional antenna. The higher you place your antenna above ground, the lower the radiation angle. A height is finally reached (depending on installation), when the “Take off” angle (Magic Height) is in the 20 degree range or lower. A radiation angle of 20 degrees or lower is an ideal angle for working long range DX. This means, the major lobe of your RF energy is radiated at an angle of 20 degrees in relation to the horizon. The horizon being zero.

The “Magic” antenna height is generally achieved when your antenna is 1/2 wavelength above ground assuming a perfectly conducting ground (earth). There are many variations in ground conductivity ranging from something very similar to an insulator (sand and broken beer bottles) to salt water which is the best with everything else in between. Different ground types make the 1/2 wavelength rule different depending on where you live. If you live by the ocean, you are very lucky indeed. If you live in the mountains, you’re not so lucky.

How do you know when you are about 1/2 wavelength above your ground? Simple math. Take 468 and divide it by the frequency you intend to operate. Again assuming perfect ground, this number just happens to be the same number you would use to cut a resonant dipole to length.

This begs the question, “Why should I bother to achieve a low angle of radiation”. If you want the strongest signal possible at a distant point, a low angle of radiation is essential. 

For instance:

You want to put up a dipole antenna for 40 meters, frequency is 7.250 MHz. Therefore, 468 / 7.250 = 64.55 feet. This height will vary depending on your type of ground, but generally it is the approximate height you would want your feed point to be located for best DX capability. It will give you a low angle of radiation which is very good for working DX. Believe it or not, some angles of radiation are better than others for working different parts of the planet. That’s another story in itself. 

Visualize this:

Suppose I have a rubber ball in my hand. I throw it as straight down as possible at the floor. It will rebound and probably hit the ceiling directly above the point where it hit the floor. It will then hit the floor again and then rebound to hit the ceiling again close to the same spot again, all the while losing energy in the bouncing process from floor to ceiling. This will continue until all the energy is used up. Notice the ball did not travel very far from the origin point.

The floor in this example, can be looked upon as your ground, the ceiling the reflecting medium or, the ionosphere. This is how your signal travels from a low dipole delivering a very strong local signal because most of the RF energy is expended locally. The signal (ball) goes straight up and straight down for the most part. The result is many hops losing energy as it moves forward very little.

Now if I throw the same ball at the floor so it rebounds at about a 20 degree angle from the floor, the ball travels much further on the first bounce before it hits the ceiling. On the second bounce, it has moved quite far from its origin point. This is how your signal travels from a dipole when it is 1/2 wavelength above perfect ground. It travels much further between hops and loses much less energy before arriving at its final destination – the DX station. Remember however, your signal has now become directional so don’t point the ends of your high dipole to the part of the world you want to talk to. No free lunch here.

With a 20 degree take off angle, your local signal is much less powerful because most of the RF energy is passing overhead and not being reflected straight down. Local stations hear your ground wave signal which is good for about 50 miles and not very strong beyond that. You receive mediocre signal reports from your 1/2 wavelength high dipole vs your low dipole. This is why a vertical is considered a superior antenna for DX vs a dipole because they have an inherent low angle of radiation when installed properly and are not directional but usually require lots of radials to work properly.

Now if you are a DX hunter, a low angle of radiation is a good thing. A low angle of radiation equals a good DX antenna but if you want a strong signal locally, then a low dipole with a high angle of radiation is better.

As we can see, to really do your best with the DX and still have a good strong signal locally, you really need 2 antennas that you can switch between. You need one antenna with a high angle of radiation and one antenna with a low angle of radiation. Quite possibly, a low dipole and a good vertical.

I hope this helps readers out there to grasp the meaning of “Angle of Radiation”.

K2WH 

73, Lee ZL2AL

Back to top^

DX Net Rant by ZL3JT

In the beginning, when God created radio, some people, including me, found that I could “work DX” on a “DX net”. In fact I went on every net I could find to satisfy my thirst for new countries and Islands in the IOTA program.

I looked up to people like Jim Smith VK9NS, Roy Jackson ZL4BO, N6FF Dick Wolf, Dr Saleem OE6EGG, Zedan Hussein JY4ZH, Percy Anderson VK4CPA… who ran these splendid sessions for those who thought it was a hellava good idea to be involved.

Little pistols with bits of wire got a chance at some “real” DX, if and when they also joined in these nets on 20m and 15m or 40m The oldest and “best” was the ANZA net on 21.205 When I had my “novice Morse” I used to listen with anxiety to the activity generated each day on the 15M ANZA Net knowing that I couldn’t participate because it was out my of my allocated frequencies… It sure was incentive to pass the Morse test and upgrade to a full call……

But over time, a couple of years or so, I realized that there was no challenge working DX with someone supervising the QSO…Saying “Over rover” at the appropriate time. …Repeat his report…You’ve got the number wrong!.  But if that’s the way you want to do it, who am I to criticize? I did it…then I got into using Morse code for DXing…..

Things changed dramatically in my mind…I could do it myself…All by myself…. It’s much more satisfying…and it’s bloody difficult to run a net on CW… So I got my                   DXCC Honour Roll all by myself, mostly with CW… I didn’t have to count any of the QSOs I had done on DX nets which was even more satisfying…But that’s just my way.

For something to do, I went on SSB nets as a DX station…It was good to do that for those who only work DX nets. But DX is where you find it …every time…. If it’s on a net, then join the net, work the DX station if you want…. What the hell does anyone else care? It’s nobody else’s business how you work DX. But I bet you won’t find nets on all bands, you will seldom find a DXpedition on a net….. So you have to forget nets, and join the pile up…

Pile ups are inversely proportional to the rarity of the DX station…remember that because you have to get craftier….. You have to make your own luck in a pile up!

73 and GD DX

Duncan, ZL3JT

Back to top^

The Founding of ZL3X

SHEARING THE FUN – THE FOUNDING OF ZL3X by Mark ZL3AB

It all started innocently enough.  I’d had a lot of fun in the BERU contest operating from home as part of the “ZL3 Earthquake Survivors” team in February 2012, when I asked if there was any interest in a serious multi-op effort in the CQ WW RTTY contest coming up in September. The answer was “yes!” and “The Quake Contesters” were born.

Starting from scratch presented some challenges.

Although we had all dabbled none of us were serious regular contesters and we were not blessed with acres of land to build a super station.  K3LR or W3LPL this clearly wasn’t going to be!

ZL in general and ZL3 in particular is not exactly flush with contesters or contest groups (ZM1A and ZM4T in the North Is being the only regular groups currently operating and there are probably less than a dozen other operators in the whole country who regularly enter any of the international contests) and we were going to need more operators than we had.

Location: Based in Christchurch, we wanted a quiet site which ruled out the local amateur radio clubs as they had stations in residential areas.  Then we had to find somewhere that hadn’t been damaged in the earthquakes we had in 2010 and 2011.

After an initial search for somewhere by the sea proved unsuccessful, I was out for a run one day pondering our options when the Port Hills, the rim of an extinct volcano at the southern end of the town, drew my gaze.  Then it hit me.  The local city council had buildings up there and I wondered if they would let us use one?  I called the council and as luck would have it, I ended talking to a guy I went to school with many years before!  “No problem” he said when I outlined what I wanted and he offered us a sheep shearing shed with a kitchen and power which was 300m above sea level and with views from the west through north to the south-east, perfect for where we needed to aim the antennas. We had our site.

Next we needed to start planning for the day so in that time honoured ZL tradition we went to the pub. There we identified some other ops to approach and set out a list of gear and antennas.  We all agreed that as this was a serious effort the first item on the list had to be a kettle for making tea and coffee!  Other than that our goal was to call CQ at the start of the contest so we determined we would strictly adhere to the KISS (Keep it Simple Stupid) principle.  Normally callsigns in New Zealand are issued with two or three letter suffixes. We decided we needed a callsign with a one letter suffix which you are allowed to request for use for special events and contests.  When we had a look at the options ZL3X stood out as the obvious candidate.

We decided to enter the Multi-Single low power category for two reasons:

1. We had major concerns about interference between stations with RTTY being a full duty mode as we had no band pass filters and the rigs were to be set up quite close together; and

2. If we managed to get it going, the “Mult” station as a search and pounce station meant that being inexperienced our ops were not under any pressure on that station to run and thereby deal with pile ups.

Come the day we were ready (or thought we were). The contest stated at 12 midday Saturday New Zealand time so the team of Phil Holliday ZL3PAH, Andrew Barron ZL3DW, Don McDonald ZL3DMC, Graeme Kerr ZL3GK and I headed up the hill at 9am.  Amazingly the Port Hills were bathed in sunshine except for the part we were going to be operating from! When we got up there visibility was down to about 30m but as Don ZL3DMC noted, “…at least we are not an astronomy club”. (Lesson one:  Conditions on a hill may materially differ from those on the flat.  Always bring warm clothes).

Now we would have loved stacked yagis and four squares but following the KISS principle we took a more modest approach.  Our antennas consisted of a hex beam on a 5 metre pole for 20-15-10m and a fan dipole on an 11m aluminium pole covering 40-20-15m.  It was supposed to do 10m as well but after we put it up we could not get it to load on 10m. (Lesson two: Always check your antennas before you leave home). The rigs used were a Kenwood TS2000 and an Elecraft K3.

Once the antennas were up we had an hour before the contest to set up the radios and N1MM on the two laptops.  (Lesson three: Never leave it until an hour before a contest to set up radios and network two laptops).  After much frustration we could get N1MM networked and logging from both radios but we could not get the cluster going or show accurate info for each laptop.  We never did figure either issue out. (Lesson four: Set up a fully functioning network in the days leading up to the contest and write all your settings down).

Because of our interference fears we put toroids on all our leads.  We even put toroid on toroids!  The rest of the lads drew the line when I started eyeing up their shoelaces and some passing sheep.  Despite that we were still worried but to our major surprise we had no interference issues.

After a “wee dram” to set us on our way we were off.  We then immediately hit a problem.  If one station was transmitting the other one couldn’t.  We couldn’t figure it out until we looked at the network set up and somewhat sheepishly noticed that the software interlock was on.  Problem solved! (Lesson five:  Read up on the software you are using before the contest).

We all had a blast as did the wind at times.  Although watertight the shed was hardly airtight with a slat floor in parts and louvres on the windows so it got pretty cold, not to mention noisy with the wind rattling the roof quite dramatically at times. After driving up the hill for the Saturday night shift and with visibility down to about 20m due to the mist, I did seriously wonder what on earth I was doing up there.  I did that shift in a sleeping bag.

From a receive perspective the site was amazing.  There was no local noise as the nearest houses were over a kilometre away and even with our low, basic antennas we managed great copy.  I will never forget seeing an Italian station signing /QRP all perfect print.

However transmit was a different story.  QST Contributing Editor Ward Silver N0AX once told me he did a study of which DXCC entities were, on average, the farthest away from all the others. The trio of ZL/ZL7/ZL8 “won” that competition going away (in case you are wondering Croatia 9A was the least distant).  From Christchurch the nearest amateur population of any substance is VK2 which is 2,100 km away or approximately the same distance as Los Angeles to Dallas.  Los Angeles to Christchurch is five and a half times further!  We realised just how far we were from the action by the number of stations whom we could read perfectly but who could not see us.  A combination of low power and the fact that many of these stations were clearly not beaming our way meant we (and they) missed out on a number of QSOs and in the case of the DX station more than likely a multiplier.  And it wasn’t just us.  Many times we saw VK’s in the same position especially in the last four or five hours of the contest.  (Lesson six – for you this time: Turn your beam when you are not busy, you never know who might be lurking off the back).

By the end of the contest and in what turned out to be the first ever multi-op effort in the CQ WW RTTY contest from ZL, we had 519 QSOs and a claimed score of 417,439 points.  We were pretty happy and as Phil ZL3PAH noted, “… contesting is a lot more fun when you do it as a team”.

Quotes of the weekend:

Don ZL3DMC “This K3 is broken”.  We later realised the Hexbeam was facing 180 deg from the direction we thought it was. (Lesson seven.  Hexbeams have a great F/B ratio).

Family friend who was staying at my house on the Saturday night:  “Why don’t you just use Skype?”

PostScript: The Quake Contesters entered the 2012 CQ WW SSB as a Multi two entry and put a lot of the things we had learnt into practice.  We had a second beam higher up, bandpass filters, more power, a reliable cluster connection and more operators.  This lead to a significant increase in our score with 2227 QSOs and over 1.9m points claimed and we had fun.  We plan to enter many of the big contests in the future.

73, Mark Sullivan ZL3AB    

Back to top^

  

My Favourite DX Stories by W4KVS

My Favourite DX Stories: Notes From a Beginning DXer

By Kim Stenson, W4KVS
[email protected]

You don’t have to spend a lot of money on a plane ticket to travel the world. From the comfort of your own shack, you too can be a globe-trotter. All you need is a radio, an antenna and the desire to make that QSO. By seeing the world through your radio, you get the QSL card without the jet lag!


Like most DXers, I enjoy reading about (and working) DXpeditions to exotic parts of the world. I have also found that there is a great deal of adventure on my end of the microphone. One of the great attractions of Amateur Radio is the ability to contact fellow operators in distant lands. Accordingly, I find a great deal of pleasure in reading about the DX adventures of hams, especially those with modest equipment. With 100 W and a modest antenna system (wires for HF and a small 3 element beam for 6 meters), I have had my share of exciting DX stories. Here are some of my favourites.

Listen to the Whole Call
One evening I was tuning around 20 meters when I came across a station calling CQ. As the operator announced his call sign I immediately recognized the SV prefix as Greece; my first impulse was to keep tuning as I already had worked several SV stations. For whatever reason, I decided to remain on the frequency and to listen carefully to the call — I soon realized there was something different. The operator was adding “stroke alpha” after his call. I recognized that it was Mount Athos, one of the rarest DXCC entities. I had recently read that Monk Apollo, SV2ASP/A, the only licensed HF operator at the religious enclave on the Aegean coast. To my knowledge, he had been off the air for at least a couple of years, and I thought my chances of ever getting Mount Athos were next to impossible.

Knowing that the airwaves would soon erupt into a frenzy, I frantically threw my call in, “W4KVS.” The operator only copied part of the call and came back with, “W4, W4?” Not knowing whether he had heard me or another W4 station, I again threw out my call, “W4KVS, W4KVS.” To my great surprise, he came back to my call and we had a short exchange. I asked him if I was speaking to Monk Apollo and he confirmed that it was indeed him on the other end. As soon as I signed off, a huge pileup ensued, one that I had no chance of breaking if I had not been the first to call. This contact is a good example of listening to the whole call. If I had not listened carefully, I might have dismissed the call as a routine SV station and missed an extraordinary DX opportunity.

Out of Africa
A similar situation took place on 10 meters one Saturday morning in winter when I came across a 3DA (Swaziland) working a huge pileup; 3DA0WPX was working simplex, and after the operator announced, “QRZ?” all I could hear was a giant whine. Any attempt to make a contact would be futile, as there was absolutely no way I could get through the pileup. I had never heard 3DA before and there was no telling when I would have another chance. Disappointed and somewhat frustrated, I moved on. Later that afternoon I was tuning 10 meters again, and suddenly I heard 3DA0WPX calling CQ again. Frantically, I answered his CQ and Andre came back to me with “You are 59, nice signal.” I also gave him a 59 report, but resisted the urge to tell him I was using an attic antenna. Within seconds, the frequency erupted into what seemed like hundreds of signals, most of which, I am quite sure, were stronger than mine.

It’s not Easy being Greenland
Pileups sometimes appear insurmountable but they often have ebbs and flows. A huge pileup can be in progress and then drop to a manageable level, only to be soon followed by another huge pileup. One morning I heard OX3OX in Greenland on 6 meters SSB working a fairly large pileup. The prefix OX is not that common on HF, and on 6 meters it is a real catch. I started throwing my call in; at the time, I was only using an omnidirectional loop antenna. After calling for a while, the pileup seemed to be getting smaller, and instead of handing out 59 reports, Ole, OX3OX, started giving out 55 reports, and finally 51 reports. The weaker stations were getting through, but could he even hear me? Finally, he did hear part of my call. After several repeats, Ole was finally able to copy my call and I exchanged reports with him. My report was 33 — not great by any definition, but I was able to get OX on 6 meters. As I often do, I listened for a while after the contact. He continued to call CQ, but did not raise anyone. I had been on the bottom of the pileup.

Persistence Pays Off
Just like everyone else, I was excited about the first DXpedition to Ducie Island, VP6, hitting the airwaves — it would be the first station to operate in a new DXCC entity. I, however, had my doubts about working it. Everyone needed Ducie Island, and I expected the pileups to be far worse than any I had yet encountered. After all, everyone needed this one. I believed my best chance of making a contact would be toward the end of the DXpedition.

One weekend afternoon, I heard VP6DI on 15 meters SSB. The operator was working a fairly wide split above his calling frequency, and I tried to determine his pattern by switching VFOs; however, I could hear very few stations calling because both the calling stations, and Ducie were located west of my location. If you cannot hear the calling stations, it then becomes difficult, if not impossible, to determine the DX station’s operating pattern.

I took the best action I could — I planted myself on what I thought to be a clear frequency and started calling. I tried for an hour or so, but I was not successful and so I gave up, believing it futile to keep calling. I turned the dial and began looking for other DX. I searched the band for a while and did not find anything interesting, so I decided to go back to chasing Ducie. I again found what I thought was a clear frequency and made a call. VP6DI came back to another call and then I heard “QRZ?” I made another call, and suddenly VP6DI came back with, “W4KVS, 59.” I shot back with a report and then revelled in my success. I still have trouble believing I actually worked VP6DI under those conditions.

Getting Guam
Asia and the Pacific area are very difficult from my location in South Carolina, and any contacts in those areas are hard to come by. Guam was one country I almost never heard, and I was very excited to hear AH2R on 15 meters during a contest.

It was the second day of the contest with only an hour to go, and AH2R was not getting many calls. It looked like I was going to be able to bag a new one fairly easily. I threw in my call literally dozens of times, but AH2R was not hearing me. Occasionally, the operator would catch part of my call and ask for “W4” or “VS.” Frustrated that he was not able to get the entire call, I decided to throw in the towel. I looked at my watch and there was only about 10 minutes left in the contest. Then I thought to myself, “Why not continue for the next 10 minutes — what do I have to lose?”

I continued calling with the same results: the operator would hear “W4” or “VS,” but not my entire call. The clock continued to tick and finally there were only a few seconds left before the contest ended. I had time for one last, most likely, futile attempt and made the call, “W4KVS.” Incredibly, AH2R came back with, “W4KVS, 59.” With that, the contest ended, but I had a new country.

Stuck in the Middle
One of the most exciting aspects of DXing is finding the unexpected. One Saturday morning, I heard a fairly weak station calling CQ on 20 meters. The station had strong audio, but it was sandwiched between two very loud stations. No one was answering the CQ and the interference was troublesome, but I had a feeling that this might be something out of the ordinary. From within the interference, I finally managed to copy the station, 4W6MM. East Timor was, and remains, one of the rarest DXCC entities, and I never thought I had a chance of working the one active station located in that country.

Two thoughts immediately raced through my mind. First, 4W6MM was not very strong. In the clear, I could hear him, but it was quite likely that he would not be able to copy my signal at all. It would be very frustrating to hear a rare DX station calling CQ with no one answering and him not being able to hear me. I could have a another possible AH2R situation on my hands. Second, I would have to time my call just right. I might be able to hear him with one of the strong adjacent stations transmitting, but not with both at the same time.

I listened for a few seconds and suddenly there was a lull in the noise. I quickly threw in my call, and to my great surprise, 4W6MM came back with “W4KVS, 59” just as one of the adjacent stations started transmitting again. Nevertheless, I shot back his report, which he acknowledged. Incredibly, I heard 4W6MM the following Saturday in a contest and was able to work him again. Both contacts lasted only a few seconds, but they were definitely among my most memorable.

Sometimes You Feel Like a Nut…
St Peter and Paul Rocks is also one of the most sought-after DXCC entities. It is a place that is seldom activated; I had never even heard a station from this Brazilian island. Joca, PS7JN, periodically operated from this remote island, but he worked primarily RTTY. I was set up to work RTTY with my computer sound card and interface, but I had never been able to have a successful RTTY contact. The few times I had tried, I was not able to make a contact.

Toward the end of one of his mini-DXpeditions, I noticed that that ZW0S, a Brazilian special event call sign, was frequently spotted, but with relatively few callers. Now was the time to see if I could work St Peter and Paul. I turned on my computer and brought up the RTTY software. I tuned for ZW0S, and suddenly he appeared on my screen. I hit the macro and transmitted, “DE W4KVS W4KVS W4KVS.” Immediately, ZW0S came back with “W4KVS 599 599.” I happily gave Joca his report and completed my first RTTY contact, which just happened to be a rare DXCC entity.

“Snappy Operators on a Completely Quiet Band”
Cameroon, TJ, is another country high on the DXCC most wanted list and I was glad to find out that Roger Western, G3SXW, and Nigel Cawthorne, G3TXF, planned a DXpedition there in the spring of 2004. One evening, I was able to copy Roger, TJ3G, on 20 meters CW working split. There was a pretty good pileup, but I kept throwing my call in. After some time, Roger indicated he would be taking a short break. I stayed on the frequency, hoping some of the others would not come back. It worked. In a few minutes, Roger came back and I got him on the second call. I was also able to work Nigel on 17 meters near the end of the DXpedition. Two great contacts!

Later, both Roger and Nigel said they thought 20 meters would be their best chance to find suitable propagation, providing long openings to all areas, and they enjoyed the “snappy operators on a completely quiet band.”

Even with a modest setup, you can have a lot of fun DXing. SSB, CW and RTTY on both HF and VHF have allowed me to participate in some great DX encounters. DXing is an adventure, and I can’t wait for my next DX experience. I know it is out there.

Kim Stenson, W4KVS, is an Amateur Extra, first licensed in 2000. Retired from the US Army, Kim is a former infantry officer who saw combat in the Persian Gulf; he counts the Bronze Star and Combat Infantry Badge among his military honors. Kim received his BA from Washington and Lee College in Virginia, and his MA from Norwich University. He is presently chief of the Preparedness and Recovery Branch of the South Carolina Emergency Management Division.

Back to top^

Pozidrive, Philips & Robertson Differences

Q: What’s the difference between Phillips, Pozidrive and Robertson (square) screws?

A: Philips drive screws are the screws that have cross-slots that look like an X, stamped into the head. Patented in the 1930’s, these were a vast improvement over the antique “slotted” screw, which tended to cam-out easily and were difficult to drive with power drivers.

Robertson (square) drive screws were patented inCanadain 1908 and address problems that the Phillips driver doesn’t quite solve. They allow the screw to be placed on the driver prior to the screw being placed in position. What this meant was that for the first time you could start a screw overhead or in a tight spot without an extra hand holding the screw onto the driver.

Pozidrive screws are the European answer to the Phillips shortcomings. The differences are subtle. At first glance it appears to be a Phillips, but on closer examination you’ll notice a second set of cross-blades at the root of the large cross-blades. These added blades are for identification and match the additional makings on the head of Pozi-drive screws, known as “tick” marks. So the marks are for identification. Identification of what?

Two features of the Pozi-drive screw and driver combination make it unique, and superior to the Phillips. First, the tip or the Pozidrive driver is blunt, which also helps it to seat better into the recess in the screw, unlike the Phillips which comes to a sharper point. This becomes a problem as the tooling that forges the recess in the head of the screws begins to show signs of wear. The recess becomes more and more shallow, which means the driver will bottom-out too soon and will cause the driver to cam-out. The second unique feature is the large blades on the driver have parallel faces, where the Phillips blades are tapered. The straight sides of the driver allow additional torque to be exerted without fear of cam-out. Knowing this, we can see why a Phillips driver will have problems driving a screw with a Pozi-recess, as a Pozi-driver would have little luck driving a Phillips head screw. One more tip. In a pinch it is possible to drive Pozi-drive screws with a Phillips driver, but you will need to grind down the tip slightly, and expect some slipping to occur.

73, Lee ZL2AL

Back to top^

 

 

How A Current Balun Works

How a 1:4 Guanella-Balun (Current-Balun) Operates – ByJerry Sodus, KM3K

1. The purpose of this article is to show how a 1:4 Guanella (current)-balun changes an impedance level by a multiplier of four; for example, 50-ohm coax to a 200-ohm antenna.
Although this is not a “how to make the balun” article, some design information is given for completeness.

2. Also, just to let you know…the Guanella (current)-balun can be turned around to go the other way; for example, a 50-ohm coax can be changed down to 12.5-ohm (say for a Yagi-antenna or a vertical-antenna). We’ll cover this later in paragraph #12.

3. BTW, Guanella came up with this idea in 1944.
In 1985, Roy W7EL gave Guanella’s idea the name “current-balun” because the balun’s output supplies equal current into/out of the output pins and that is a good thing.

4. It is important to put out of your mind any idea about flux-linkages and conventional-transformer action. Those concepts have nothing to do with this article.

5. The 1:4 Guanella (current)-balun is made from two 1:1 Guanella (current)-baluns.
Except for winding direction, they should be as identical in construction as possible to minimize any variation in signal delays; variations will increase signal loss at the higher frequencies.

6a. The 1:1 Guanella (current)-balun can be made up in several different ways:
A) coiling coax,
B) winding a transmission-line (coax or two-wire) on a toroid-core or rod; ferrite core/rod preferred,
C) threading coax thru ferrite-beads.

6b. Figure 1 has the usual schematic used for a 1:1 current-balun.

6c. To emphasize that the transmission-line mode is working here, lets use the schematic as in Figure 2.

6d. Here is a key point.
We’ll assume that any signal loss thru the balun will be small enough that we can ignore it.
So, whatever voltage is at the input of the 1:1 balun is what we’ll see at its output.
In other words, we assume the signal’s voltage-level is not attenuated by the 1:1 balun.
In practice, we can approach this goal by using high-quality transmission-line and keeping its length short.

7. You connect up the baluns in this way as shown in Figure 3 below.

7a. The inputs are in parallel.
That means that any current going into terminal P3 splits in two, half goes up to terminal 3 and the other half will go down to the other terminal 3. At terminal P1, the currents coming out of each terminal 1 combine at P1 to flow back to where it started. Although P1 and P3 are where we will eventually the feed-line from the transmitter when we use the balun, for us right now, the feed-line is not connected.

7b. The outputs are in series.

Notice that if we were to connect an ohmmeter to P1 and P3 at this time, we’d read a short-circuit.

7c. Next connect a load ‘RL’, which we assume is a just a resistor for our purposes at this time. See Figure 4.
You may recall that a resonant-antenna is just a resistor, in other words, a pure resistance (no reactance). It’s interesting that, in Figure 4, the current going around the “inside-loop” never gets to the load RL. The “inside-loop” is from P3 going down to balun-A’s terminal 3, then to terminal 4, up to balun-B’s terminal 2, over to terminal 1 and then to terminal P1.

8. There is a term “input impedance” and we’ll use the symbol “Zin” for it.
In case “input impedance” is a new idea for some, here is a short explanation…
For us electronic folks, it is the value of impedance we’d measure at a test-frequency if we could connect up a special kind of alternating-current ohmmeter to terminals P1 and P3 in Figure 4. That value of Zin would replace the entire circuit to the right of P1 and P3.
For us right now, we are only concerned with the idea of “input impedance” and not with any actual value.

9. We’ll use the schematic in Figure 5 to find the power going into Zin.A key point here is to remember this is really the power going into the input of the 1:4 balun (at P1 & P3). In Figure 5, we are not concerned with the transmitter or its output-resistance. All we really care about is that there is Zin and a voltage across it; we’ll call that voltage “V”.

Recall that power going into a resistor is equal to ‘the voltage across the resistor’ times ‘the voltage across the resistor’ divided by ‘that resistance’.
So using our symbols, we can write the “power into the 1:4 balun” equals “V times V divided by Zin”.

10. Next we need the power going into the load RL. So, we need to know the voltage across RL. Here is how we’ll figure out what its value is.

10a. Recall that the voltage across P1 and P3 is V.
This is the same voltage across pins 1 and 3 at each of the 1:1 baluns.

10b. In step 6d, it is written that the same voltage V will be at each output of the 1:1 baluns.

10c. Step 7b has the outputs of the 1:1 baluns connected in series. So this means V plus V equals 2V is across the load RL. (If you have trouble understanding this, perhaps this may help. Just for now, pretend that each 1:1 balun output is a battery. So we have two batteries connected in series; just like in a flashlight and the light-bulb is the load. If each battery is 1.5 volts, we’d have 1.5 volts plus 1.5 volts equals 3 volts across the load.)

10d. The “power going into RL” is “2V times 2V divided by RL”.

11a. Now we are at the KEY section; the reason for this article. We are assuming there is no power lost in the baluns and that is a reasonable approximation throughout most of the 1:4 balun’s passband. We can write…”POWER INTO THE 1:4 BALUN” equals “POWER GOING INTO RL”. Paragraph 9 gives the “power into the 1:4 balun”.Paragraph 10d gives us the “power going into RL”, so we can write here… “V times V divided by Zin” equals “2V times 2V divided by RL”. Doing all the algebra, we come up with …..”RL equals 4 times Zin”. So we have proved we have a 1:4 impedance-ratio.

11b. An example ……….if Zin is 50-ohms, then RL is 200-ohms.
11c. Another example…..if Zin is 75-ohms, then RL is 300-ohms.

12 If we turn the 1:4 balun around to get a 4:1 balun, we can step-down in impedance.
For example, 50-ohms divided by 4 equals 12.5-ohms (maybe for a Yagi antenna); see Figure 6.

13. Comments about the transmission-line used in a 1:1 Guanella (current)-balun:

13a. The value of its characteristic-impedance Z0 (that is Z and a zero; pronounced Zee naught) is important.

13b. The 1:4 balun has a low impedance side and a high impedance side. Whatever the high impedance side is, divided that value by two and that is the characteristic impedance to use in the 1:1 Guanella (current)-balun.

13c. Here are examples of some values for 1:4 Guanella-baluns…
for 50-ohm to 200-ohm, Z0 is 100-ohm.
for 75-ohm to 300-ohm, Z0 is 150-ohm.
for 50-ohm to 12.5-ohm, Z0 is 25-ohm.

13d. You can make your own transmission-line (two-wire or coax); see Sevick’s “Transmission-Line-Transformers”.

13e. The more you deviate from the design Z0, the more power you lose at higher frequencies.

14a. The 1:4 concept can be extended to other ratios like 1:9 and 1:16 and 1:25.
14b. But more 1:1 baluns are needed; the 1:9 uses three; the 1:16 uses four, etc.
14c. The Z0 formula changes also; for 1:9, divide the high impedance by three; divide by four for the 1:16.

15. For completeness sake….it is possible to make a 1:4 Guanella-balun on just one core (in other words, two 1:1 baluns on one core paying proper attention to all pertinent details); however, that design approach should not be used if the load is grounded (virtually or actually) at its center point.

I hope this article is of some benefit in explaining how the 1:4 Guanella (current)-balun “does its thing”.

73 Jerry Sodus, KM3K

South-Mountain-Radio-Amateurs Club

Back to top^

 

Audio Dynamic Range

Audio Dynamic Range

What is you audio dynamic range? This mostly applies to SSB transmissions but could also apply to FM and AM as well. Simply put it is the difference between no modulation during key down and your modulation peak in dB.

Your dynamic range listed below will give you an idea on how your audio is perceived by the other contact.

  • 10 dB, which is very harsh and tiring to listen too. Much background noise including fans, road noise, air-conditioning, dogs barking and in general background clutter noise. Your contact will ask for repeats a lot and in general your QSOs will be short.
  • 20 dB, decent audio range with a little audio background noise. QSO’s will last longer. Very little repeats. Most stations fall into this category.
  • 30 dB, your contacts will complement you on you audio, tonal quality aside; you will find folks will like to listen to your transmissions. Communications in weak conditions will be generally more successful.
  • 40 dB, you are now into broadcast quality transmissions. This is not easy to obtain but with proper microphone techniques and mic gain settings most any transceiver can obtain this level.
  • 50 dB, this is where you need to be if you plan on running a Linear Amplifier. With a +30 dB over S9 signal to your contact, your un-modulated signal will still be an S6 on their receiver. Poor dynamic range is the reason people ask if you are running a linear amplifier.

For FM you will need a deviation meter but with a good oscilloscope you could use the same method as you would use for AM. For AM you will need an oscilloscope to look at voltage level from no modulation and modulation peaks. For both FM and AM, this can be derived from a monitor receiver speaker output. SSB is much easier. Look at the peak signal as monitored from a nearby station. The difference in the peak reading to your modulating signal to the level received while not modulating is the dynamic range. If you have a lab grade watt meter you can look at the power output from the radio or amplifier. The formula is:

Log (power max/power min) x10 =DynamicRangein dB.

An example of a 1500 watt signal with a non modulation level of 100 mW is shown below:

Log (1500/.100) x10 = 31.76 dB

As you can see, 100 millawatts can transmit quite a lot of signal or noise. Some of this noise could be generated in the transmitter but generally it is from the microphone environment. To check you audio level, transmit into a dummy load and watch the output with no modulation. If you see a level indicated, turn you microphone gain down to zero. If the level drops to zero your microphone level is the problem with your low dynamic range and your audio environment.

Several things can be done to improve you dynamic range.

  • Try to pick a quiet place for your station.
  • Close the door to your shack.
  • Use the microphone between 3 and 6 inches from your lips.
  • Your ALC should read 10 dB or less.
  • Avoid excessive compression. It is mostly microphone gain with a little filtering.
  • Speak directly into the microphone, not on the side.
  • Use a wind-screen (foam rubber) over the microphone.
  • Be aware of cooling fan noise. Placement of fan related gear (amplifiers) is important.
  • Use a suspended microphone. They pick up less desk noise and vibration.
  • Avoid a room that has no rugs or drapes. Echoes don’t help and can make communication quality very poor.
  • Make sure the TV and stereo cannot be heard.

These are the most prevalent items I hear being done in QSOs. If you’re mobile, roll up your window. Some FM mobiles have so much vehicle and wind noise their transmissions are unintelligible.

These are just a few suggestions on making your home station and mobile environment much more pleasant to listen to. Work with other hams for a critical ear. Now have fun.

Mike Higgins – K6AER

 Back to top^