VHF Propagation

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

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.

My Radio Station

This section lists my radio station pieces and is never complete. As with technology - my ham radio station is always upgrading! One thing I would like to stress is you can NEVER have too many radios and related gear!

My main station radio is a Kenwood TS-2000 right now (right of center). I use this on all bands/modes. It works great on just about everything. For being an all-in-one rig you really cant beat it with a stick! The filtering in it is good and the audio just sounds spectacular (its a Kenwood, what do you expect?). Now, the receiver performance overall isn't the greatest. It has trouble in crowded bands and high QRN. Its not a high-performance rig so this is to be expected, however. On VHF/UHF this rig kicks some butt. I have worked a few VHF+ contests with it and I constantly hunt grids on 6m with it. If you had to have just ONE rig this is the one to have. Nothing else like it.

My backup radio is an IC-718 (left of center). I recently fixed it. The power output dropped down to 50w max. Its been doing this for about a year now. I never got around to fixing it because, well.. I don't really use it much. So, after some investigating I found the problem - there was a 4 volt drop at the rig when I keyed up! I tested the power cable and found the drop to be across the stock fuse blocks. I cut them out and directly soldered the two parts back together. My cable is fused at my distribution panel anyway, so I'm still protected. Now it runs fine! The performance of this rig is far less than the TS-2000. I don't have any filters in it, just UT-106 for DSP noise reduction (which helps). However, the rig is DYNAMITE on PSK31 and other digital modes! This was the first ham radio I ever got. I got it partially as a Christmas present in 1999 or 2000. I used it for SWL before I had my license.

Before I got my TS-2000 I got the Ranger RCI-5054DX (25 watter, not the 100 - left side middle shelf) for 6 meters. 6 meters is an interesting band (hence its called the Magic Band) - you can get out famously with 1w to a coat hangar when it opens. So, this little rig actually does pretty well - minus the fact it has no DSP/filtering. This rig is usually on 6m monitor duty when I'm in bed or when I am running HF on another rig and want to/can monitor 6.

The power behind my station is an Astron VS-35m (left side top shelf). This provides 25A continuous, 35a peak. This is more than enough for my needs. If I fire up everything on the table and plug my laptop computer in to it as well I still only draw 25 when I key one of the HF rigs at 100w. Not bad! It does make a nice heater, though. Good in the winter, bad in the summer. I typically run my shack at 14 volts.

My main microphone is a Heil Gold Line GM-4 (on the boom, hovering above the IC-718). I know Bob Heil. I stop by and say hi to him at Hamvention every year. He always recognizes me. I wouldn't say I know him well, though. For anyone who doesn't know who he is - he is a pioneer in pro audio. He's worked with groups such as The Grateful Dead, the Who, Jeff Beck, the Eagles, Peter Frampton, and Joe Walsh, among others. Bob holds the patent for the Talk Box, made famous in Peter Frampton's solo in "Do You Feel Like We Do" (in fact, that was a prototype Bob sent to Peter thinking he could make use of it - and that he did!). Anyway, the GM-4 has the HC-4 element for DXing - it cuts like a knife through the noise, not the most pleasant to listen to but it it packs a punch. It also has the stock full-range element for everyday use. In fact, the full-range element sounds so good I use it for recording acoustic guitar as well. I bought the shock mount for it along with a PL-2 boom. Hey, if you're going to have a nice mic you gotta mount it to a boom. A foot switch on the floor controls PTT for hands-free operation (or DXing/contesting and logging at the same time).

My antenna tuner is new last winter (06). It is a Palstar AT-1500CV (right bottom under cabinet). I bought it for myself as a Christmas present. I have needed a tuner and now I have one, the best one I could get. These are actually made right here in Ohio, over in Piqua. I met Paul, the owner of Palstar, a couple years back. I was researching tuners and found out about Palstar and them being in Piqua. So I e-mailed Paul and asked if I could drive by and take a look at their products in the shop. He agreed, so I went over there on a Saturday and got a personal tour of Palstar! I have to say, I am impressed with their products and quality. I am in no way associated with Palstar, other than Paul is a friend, so I'm not getting paid to advertise for them - my opinion here is my own: After looking at other manufacturers tuners and seeing the parts in them compared with the parts in Palstars.. well, there's just no comparison! Palstar beats the pants off the competition (Ameritron, Vectrionics, MFJ, Ten Tec, Nye Viking, Dentron, you name it). Palstar is an American company, their parts are made in America, their products are assembled in America, and, not surprisingly, they're the best!


My CW (Continuous Wave, otherwise known as Morse code) key collection includes a couple Vibroplexes - an old mechanical Bug (right of center) and a Code Warrior Jr (far left)., an RA P4 iambic paddle (far right), an MFJ economy strait key (left of center), and an MFJ micro-paddle (not shown). My main key is the RA P4. It is made by a good friend of mine, Jerry K8RA. I met Jerry doing a photography project on Ham radio operators and their stations. One of my other friends recommended I go see Jerry. Boy, I must say hes quite a guy - and his shack is ONE OF A KIND! The Vibroplex bug was given to me by Dick, W8JLY, before he passed away. I used to talk to him on the 145.110 repeater in Dayton all the time. I was on there talking to the usual group and we got on the topic of CW. I mentioned I love it and just about all my QSO's on HF are CW. So, when I signed off (it was a school night, I remember that) I left the rig on for a few minutes and I heard Dick tell Shirley, N8LX, who apparently had the bug at the time, that he wanted me to have it. So, that was pretty special. I still like to bang this old thing around occasionally. They take a LOT of force and technique to get the code out right, but they sure have a unique sound - and every operator has his/her own unique "fist". The Code Warrior Jr. was my favorite key to use before the P4. It uses magnets instead of springs so the action is unique. I like the feel of it. However, the weight is a bit of an issue. That's where the P4 is superior. The P4 weighs in at 5 POUNDS! It wont go ANYWHERE while banging out the code.

Other equipment on my list for the future: I have my eye on an FT-857D. I need a small rig I can toss in a back pack for hiking/camping/PM. The 817's RX isn't very good and it only runs 5w max. The 857D doesn't suck down much more current on low power/rx as the 817 and it has a VERY good RX and has the ability to transmit a full 100w. Very nice. Also, I'm looking at getting a high-performance HF rig. So far I am looking at the FT-2000. I like the way it looks, the price is right (the least expensive "high-end" rig out there right now), and it has 6 meters too. However, I have heard some bad reports about it. Since I'm not going to be buying one right now Ill be able to watch it evolve. Maybe Yaesu will make an MP and MK5 version like they did their popular 1000 series. Hopefully in the next year they will fix some of the bugs. Who knows - maybe a software update will be all it needs.

Other stuff shown in the picture: ARRL world map (tape lines are beverage directions for this winter, not for this QTH though - no room), Teaberry T Command CB (left on top of speaker), Astatic D-104 (on top of shelves, the silver chicken-choker, or lollipop if you prefer it called that), old Gateway computer (note the HUGE monitor - I hate that thing, from about 97-00), and the very far left is some of my audio gear - Behringer MXB-1004 mixer (absolute CRAP - Bheringer is the MFJ of pro-audio, maybe a little better, their soldering is actually pretty good but their stuff doesn't last) and a Dynaco 80w kit amp on top of a classic Technics receiver. The deer head is from my grandparent's house in Minnesota. They moved to Arizona and almost threw them out (there is another, not pictured). Those can't be thrown out! They're too cool!

Lake of the Woods, EN39 on the Air

My family has a small island on Lake of the Woods in Ontario, Canada. It is in Sabaskong Bay, about a mile nearly due west of the southern tip of the Nestor Falls airport runway. I go up there every year. There is just no other place like it, and nothing could ever replace it.
Since I have been a Ham radio operator I have taken my radios with me to operate from there. The Maidenhead Grid Locator on the island is EN39ad. This is a location designator Ham radio operators exchange on the VHF bands and higher. EN39 happens to be a rare place to operate from so I have a blast when I am up there!

This past trip I made all of my contacts on the 50mHz band (6 meters). I had more contacts this trip than all other trips COMBINED (that's the previous 5 years). E-skip was great. I caught band openings from Washington state, down to Texas, and over to New England. It sure is fun to call "CQ 6 meters this is VE3/KC8QVO Echo-November 3-9" and hear dozens and dozens of stations all calling ME! It is a very powerful, exciting feeling. That's what makes all the effort of setting up the gear, and the expense, all worth it.

The equipment list is pretty extensive. I basically brought every radio and accessory I own, minus a few HF antennas and masts. I had both HF rigs - TS-2000 and IC-718. I took my IC-207H out of the truck and used it for weather band RX and monitoring the FM stuff - including the marine band. I even had my Cobra 29nwst CB on the table. There actually was quite a bit of activity on the Chicken Band. Every time I turned it on there were people talking. 2 meters was dead - no one on the band, and no repeaters to hit. My RCI-5054dx was used as a night-time 6m monitor. I didn't want to leave the 2000 on all night. I ended up loosing the LED back lighting on the 5054 from continuous use, but the radio still works. That came in real handy when Es started up at weird times. They don't call 6 meters "the magic band" for nothing. Power came from my Astron VS-35m. The rotator was my trusty G800-SA. The big box there with the two vernier drives is my AT1500CV tuner (read my post about "Antenna Tuners?" if you want to get in to that topic). That was supposed to be used on HF, but I never got around to running much HF. The mic is a GM-4 on a PL-2 boom and shock mount. The big brass thing is an RA P4 key.
I ended up using the TS-2000 the whole time. I had the 718 because I was planning on running a net on 40 meters so people would be able to set up scheduled contacts and know when I was on the air. Unfortunately, 40 meters had a lot of noise and was unusable. Same goes for the computer - that was for digital modes. Even though I could have run WSJT on 6 and 2 I didn't have any way of setting a sked.

The antennas were my regular beam antennas. A50-5S on 6 meters, 13B2 on 2 meters, and A440-21ATV on 70cm (yes, that is M2's ATV antenna but it does run fine at 432 also). Please see my section on the "Portable Rotatable Mast" for more information on how these were actually installed. For HF I had my Tarheel model 200 screwdriver. That also worked on 6 meters. Once I found out about the noise problem I scrapped the idea of a 1/4w vertical for 40. That would have been another 30 some feet of mast that would have had to be erected, and for a band with a lot of noise it just wasn't worth the time and effort.

The trip wasn't all radios, though. My grandfather lives here in the summer. He turned 80 years old when we were there so we had a nice birthday party with a lot of our family friends and locals. It was a good time. Other activities on the island include: gathering fire wood (yes, it is the middle of the summer and it does still get cold at night), maintenance (mother nature does a hell of a job in that climate), as well as other chores.

When the work is done and you need some relaxation there are lots of ways to do that! Being on the 7th largest lake in the world, there are unlimited places to explore and places to fish. Just make sure you have a GPS handy so you can route yourself back home. Its easy to get lost on the lake.

My Grandfather netting a Walleye


How about a trip around the bay in the sail boat?

Here is a beautiful shot of the sun setting on the lake. We were coming home from dinner over at Green's.

Portable Rotatable Mast

I have been trying to make my antenna system as portable-friendly as possible for operating on my family's island. That has been much easier said than done, however. I run fairly large beams on 50, 144, and 432mHz - all rotatable . 5 elements on 50, 13 elements on 144, and 21 elements on 432. These antennas require a significant amount of strength to hold up. We get very strong winds on the island in storms so nothing too light duty would work. However, at the same time everything needs to fit in the back of my pickup truck for the 2 day trip there and back (that's one way, its roughly 20 hours - of driving).

To start with the theory behind my current mast system Ill say this: I am pretty much a one-man-band when it comes to setting up this stuff. That's 3 relatively large beam antennas and a rotator for positioning that need to be raised in a portable setup by one person. Sounds like a lot of work. To add to it I am setting up on a slab of granite that slopes fairly sharply down then drops off in to the lake. It doesn't sound like a very good place to set this up. Its not. Click on the picture to and enlarge it.See where the guy lines go? Right down to the edge of the water. A couple years ago I went for a swim setting up.

The first problem in my mast set up was to figure out how to make my upper mast rotatable and mast mountable. For one antenna this is a piece of cake - you stick about 2' of mast in the top of the rotator, bolt a mast adapter to the bottom of the rotator, and stick it up as high as you want to go on a main support mast. Done. Maybe some guy lines for added support, if needed.

This is all fine and dandy for 1 antenna. However, when you stack antennas you have to consider the distance between those antennas. Every antenna interacts with every other antenna in close proximity. To minimize loss of performance you need to separate these antennas. In portable setups, the general rule of thumb is to separate the antennas by as much as you possibly can. Getting to the edge of interaction is probably impractical. Since there is only one direction to go, up, that means the antennas need to be separated by stacking one on top of the other going up the rotating upper mast.

Back to the 1 antenna on the rotator. The distance between the antenna and rotator is not that much of an issue, however as the frequency goes up the image of the rotator increases thus the distance (in wavelengths) between the antenna and rotator increases. Theoretically, you could mount a 50mHz beam right to the top of the rotator (no spacing) and it would be fine (there would be interaction, but not too much). The image the roator shows to the antenna is small. There would need to be much more space (in wavelengths) at 432mHz between the rotator and antenna because the image of the rotator is MUCH larger to the smaller frequency, it is almost 1/2wl wide. However, this spacing would only be roughly 1/2wl - or a tad over 1'. At this distance the force on the upper mast on the rotator when the wind blows would be very minimal. The rotator would have no trouble holding all of this.

To bring this all back to my setup: I have 3 antennas. The upper mast I have is roughly 18' (it is a section telescoping mast and fits in my 6' truck bed). To get the most performence out of my antennas I need to space them out as much as I can on the mast. The further from the rotator I go the more the wind loading of the antenna stresses the rotator. 18' of upper mast is WAYYYYY too much for the mast clamp to hold. It would snap off like a 100lb weight would do to a broom stick if it was only held at the base. The solution to this wind loading problem is the force applied to the mast clamp on the rotator must be RE-DIRECTED. The amount of force can not be changed, it is what it is. However, the direction that the force acts on the rotator CAN be changed. Currently, the force on the clamp is a vertical snapping force. Hold a pencil straight up by the eraser and push the lead tip over - see how hard it is to hold back the pencil from leaning over. You cant do it. Its a lever - and a lever with a TREMENDOUS amount of mechanical advantage. Instead of a snapping force, why don't I change the force to a horizontal shove so the mast clamp is holding the mast in place rather than the mast trying to break off the clamp? Can I do that? With therotator by itself, no I can not. I need something else. I need to support the upper mast at some point above the rotator. The higher this point is the more mechanical advantage the BOTTOM of the mast has to HOLD BACK the wind loading of the antennas above.

So now my problem has become how to support the upper mast at a point above the rotator to change the force applied to the mast clamp from a vertical snapping force to a horizontal shove. What this calls for is to mount therotator inside of something rather than on top of the main support mast. In permanent radio antenna installations the rotators are mounted inside of a tower. The upper mast goes from the mast clamp on top of the rotator, through a "thrust bearing" at the top of the tower, and up to the antennas. My rotator is mounted to a mast, not inside of a tower. What I need is a bracket to mount the rotator in that also supports an upper mast at a point higher than the rotator.

My solution does just this. If you look at the close-up picture (from 07 Sept.ARRL VHF contest) you can see the black bracket the rotator is bolted to. The mast is supported high enough to where the force on the rotator is redirected, yet isn't close enough to where the mast would just kink over. I did not do any calculations on this to show where and how much force is applied, I just guessed at it. For a portable system it works fine.

The next task in my mast evolution is figuring out how to raise this. I would estimate the weight of the rotator/antenna system to be 100-120lbs. Considering this has to sit at the top of a mast, that's a LOT of weight.

My first idea was to use a pulley system and tilt up the mast. Needless to say, this was a terrible idea. The lower mast bent too easily with the weight of the antennas and was very unstable once off the ground. It wanted to swing all over the place. At first the idea sounded like it might work, but in practice it did not.

The next idea was to set up the lower mast on the ground real short. Then mount the antenna system to it. Then raise the mast and antenna system and put mast sections underneath to build the height. Well, with over 100lbs of dead weight flying above your head this was NOT a smart idea, let alone the difficulty in holding on to a pipe less than 2"OD with that weight wanting to shove it in to the ground.

What I needed was a way to erect the main mast entirely before the antenna system. This required the antenna system to be on the ground while the mast went up first. To do this, I built a "tram". The rotator bracket mounts to a pipe that slides on the outside of the mast. With the help of the pulley blocks from the tilting method the antenna system is hoisted right up the mast.

This sounds simple. Well, its not THAT easy. As with the other ideas, there are problems. The biggest one is the wind loading and weight of the antenna system on the mast. The mast is not nearly strong enough by itself to hold the antennas in the wind. Maybe 1 or 2 sections could, but not up at 25'. Its a giant noodle - with over 100lbs of dead weight wanting to bend it back down to the ground. What it needs are guy lines.

So, I have a tram for the antenna system that needs to be guyed. The guy lines do one thing in two ways: They keep the mast standing by 1:transferring the force of the wind pushing on the antenna system to the guy points and 2: also sending that force down the mast in to the ground. Problem: the guy lines will prevent the tram from going up. So, the tram must be raised in increments. Each time the tram goes up I must loosen the guy lines and then raise some more. Its a cycle. Not fun, but it works. Now the antennas have a way of getting to the top of the mast and able to be rotated. Since the mast cant move at the top from the guy lines, I'm off to the races!

Not so fast. The antennas must be able to rotate, and the position must be calibrated so I know what compass heading my signals are going. The rotator solves the issue of rotating the antennas, but how do I hold that position? With guy lines attached to the tram the force of the wind could spin the whole thing around and tighten up the guy lines even more, like the reel on a winch, causing failure in one of the lines. This is a volitile system. A failure in ONE of the lines is a collapse of the mast - its that simple. That's a big safety hazard, not just for people but for the cabin. Imagine 100-some lbs worth of metal falling from 20 some feet on to the roof... or the raised deck...

What I need is to prevent the antenna system from winding up the guy lines - causing the loss of my heading first, then the failure of the whole system. To do this, the guy points on the tram must be spaced away from the tram and held rigidly in place. Having the guy points away from the tram increases the mechanical advantage the guy lines have on centering the mast. On commercial guyed towers they have a star mount. What this does is exactly what I described I needed - its a bracket that places the guy points out away from the tower. However, the star mounts on most commercial towers have twice as many guy lines attached - 6 rather than 3, 2 per face. Since my system is not a permanent installation I should be fine with 3.

My star mount is made from 5/8" square tubing with a flat 1/8"attachment point in each corner for my shackles (see side photo, the angle supports on the tram point down when erected). The star mount is small enough to fit in the truck bed under my fiberglass cap (the low one, not the tall one with the windows) yet as big as I could make it to maximize the mechanical advantage for the guy lines to hold the mast in the right position.

This past summer (07) I was able to get this system up entirely by myself. It was a challenge. However, it went up in a controlled environment and worked flawlessly throughout the week I operated. The bigger challenge was getting this down. I ended up using the help of one other person because I forgot to undo a redundant guy line I attached and it left me holding on to the system on a ladder and I couldn't let go hehehe. So, there are still bugs that need to be worked out but a working system is in place.

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

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!

Capacitance Hat Pedestrian Mobile Antenna

This idea stemmed from the coming HFPack gathering at Hamvention this year. Their calling frequency is 18.157.5usb. I have never really done any /PM operating before so I figured I would give it a shot. The radio I am probably going to use is my IC-718. I know, it isn't a very compact radio, but it is fairly light and will get me on the air.

Another note before I describe the idea is all of this occurred in the course of about 6 hours - from the initial idea stimulation to the construction and getting on the air (tuned up, no contacts though).

My first idea for the antenna was a whip/mast that is 6' tall with a cap hat on top. The mast was to consist of a PVC pipe supporting a wire. The cap hat would be made out of tape measure pieces secured to a PVC cross connector.

Once I started getting materials together I realized I had some aluminum pipe that I could use for the mast instead. It is the center section and one outer section of the separation boom for two Cushcraft 13B2 antennas. I bought 1 antenna and this boom used from a guy. The pipes
have come in handy for all kinds of things! Anyway, the pipe works very well for this project because the two sections telescope. That means I can adjust the height of the antenna to tune it.

So, now my idea has taken a new form - from the original PVC pipe mast with the cap hat to a telescoping aluminum pipe with a cap hat. The cap hat is still made out of tape measures, 30" of 1" wide tape for each spoke.

One big question I should address with this antenna is how it actually mounts to the pack. Well, my back pack has a pocket right against my back that is supposed to be for a water bladder. So it has a zipper right on the top of the pack. It is on the pack side of the back plate/frame. So, I made an H-frame out of PVC. It uses a T connector on the bottom with two equal pieces of pipe
pushing out







Edit: 8/24/07

Its been a long time since I posted anything new here. I figured I would update this first.

The antenna works. I ended up using my TS-2000 at Hamvention /PM. Yep, it was heavy. The rig and my lawnmower battery for power were just under 50lbs. With my pack and all loaded for Hamvention I was toting around 60lbs. Not fun.

The H-frame was poking my tailbone the whole time, so I got a nice rash there. However, that was due to the battery pushing against the H-frame. This setup probably wont be too bad with a lighter rig/battery (such as the FT-857D and a 12 or 18AH AGM/SLA battery.