VHF/UHF Amateur Radio

Life Above 30 Megahertz

For many radio hobbyists, their first exposure to Amateur Radio comes from listening on a scanner to hams operating on the FM repeaters in the 2-meter or 70cm bands. Most any scanner will readily tune one or more local ham repeaters, and once the radio hobbyist ventures outside the police/fire/EMS bands and decides to see what else he or she can pick up on that scanner besides the local emergency services, it's only a matter of time before the local ham club repeater is discovered.        Sometimes this is a discovery that results in the listener eventually becoming a licensed radio amateur - the listener likes what he or she hears, and so decides to join in on the fun and becomes licensed, usually at the entry level, Technician Class license...and because the privileges granted by the Technician license are all on VHF/UHF (unless the licensee also happens to know Morse Code and passes Element 1 as well, in which case he/she also gets some HF privileges), the vast majority of new hams first show up on the air on the VHF/UHF bands. Most often, it's on 2 meters, which is easily the most popular of these bands, for several reasons.        First of all, there is literally a bewildering array of equipment available for 2 meters, at very affordable prices. While even a very basic HF rig will cost upwards of $600 (just for the rig, and not counting the needed accessories), a new ham can get a 2m HT or mobile rig for around $150 new, or even for much less by shopping around at a hamfest. A mobile 2m magnet-mount antenna can be had for well under $50, so the new licensee is on the air on 2m for under $200 and is thus fully equipped to enjoy 2m FM repeater and simplex operation on what has become ham radio's most widely used band.        With the addition of a power supply and a simple vertical antenna on the roof of the house or garage, the same radio can be used in the house. Make it a decent beam antenna with a rotor to turn it with, and you now have a range of about 100-150 miles in all directions, within which you're likely to find hundreds of hams to make friends with. For a little more money the rig can be a dual-band model that also covers the 70cm band, giving you yet another popular band to operate on.        Communications on these bands is largely line-of-sight. This does NOT mean you have to be able to see someone in order to be able to talk to them on the radio! It means the two stations' antennas have to be able to "see" one another in order for the dignals to get back and forth between the two stations' antennas. If you're using a handheld transciever (HT) and your antenna is the lowly "rubber duck" supplied by the manufacturer, your range will be a lot less than if you have a vertical or beam antenna on the roof of your house (or even a magnet-mount antenna on the roof of your car). The key to determining line-of-sight is primarily in the height of the two antennas. In fact, there's a rather simple (though for some reason not that widely known) formula you can use to determine the line-of-sight range of your antenna, so that you can easily figure out when you're putting up your antenna, how high it has to be in order to talk to your buddy on the other side of town.        Now, once you have your antenna and radio hooked up...ahem...hey, you there in the back with your baseball cap on backwards - stop interrupting me, or I'll have to get my friend Bubba - who is extremely large and extremely mean - to twist your head around until your hat's on straight! Oh, alright...what is it? Oh, I see, you want to know what this magic formula is for determining line-of-sight range of your station! Well, okay, that's a reasonable request...so here it is:        The line-of-sight distance from your antenna to another antenna is equal to the sum of the line-of-sight distances to the horizon of both antennas. The line-of-sight distance of an antenna to the horizon is equal to 1.4 times the square root of its height. It's a lot easier to calculate than it sounds, so let's have an example to show you how it works.        Let's say you want to monitor the local cops, and their antenna is a hundred feet above ground. The square root of 100 is 10, and 1.4 times 10 is 14, so the distance to the horizon from the police antenna is 14 miles. Your antenna is 25 feet up. The square root of 25 is 5, and 1.4 times 5 is 7, so the distance from your antenna to the horizon is 7 miles. Add the two and you come up with 21 miles. If you're within 21 miles of the police antenna, you're within line-of-sight range and should be able to hear them just fine.        Now, considering that some ham repeaters have antennas that are hundreds of feet above ground, sometimes even over 1000 feet up, if you do the math as explained above, you begin to understand how you can still have line-of-sight range to a repeater even when you're on a rubber duck in your basement. A repeater antenna at 1000 feet has a distance to the horizon of just over 44 miles. You should also note that this is pure theory - based on the theoretical premise that the range of the bands is line-of-sight from the bottom of the antenna to the horizon - and that in practice things don't always work that way because buildings and other objects get in the way and block or reflect signals. The formula is nothing more than a starting point for you to use, to find an approximate line-of-sight range of your antenna over level ground. If you live in a hilly region, your mileage will vary.        Okay, as I was saying, once you have your antenna and radio hooked up, the first thing to do is to LISTEN. This is very important. You don't learn anything by talking - unless it's to ask questions - but by listening first, often your questions will be answered before you even need to ask them. Spend some time listening to the local repeater. Learn who the regulars are, take note of any local operating practices you ought to be aware of, so that when you do finally transmit you'll be able to act like you know what you're doing (even if you don't). THEN go ahead and, when the repeater isn't busy, toss out your callsign, and have fun making your first contact.        Oh, yeah, you do have a callsign, don't you? If you don't have a license, don't even THINK of transmitting until you do. Unlicensed operation is a serious violation of FCC rules, and licensed hams want nothing to do with you unless you have the appropriate license for the band you're operating on. If you don't have the license, you're a bootlegger, a pirate, or one of the other, uncomplimentary names we hams have for unlicensed operators - the rest of which have no place appearing on this web page where young and impressionable minds might read it, so I won't print such filth here - and the local hams won't wait too long to track you down and turn you in to the FCC, which has a long history of socking violators with huge fines for operating without a license - so don't do it. Get the license first - it's not that difficult - then enjoy the hobby the right way!

Beyond Line-Of-Sight

In the above discussion of line-of-sight range to another station, you will recall that I mentioned that line-of-sight is largely a theoretical concept and that in practice, things don't always work the way the theory suggests they should. Being the pessimist that you are, you probably assumed that your range would be considerably less than the theory would suggest, right? Go on, admit it! Fact is, though, that on the VHF/UHF bands, there are also factors which often extend our operating ranges far beyond line of sight.        On the most popular of these bands - 6m, 2m, and 440 - something called "temperature inversion ducting" or "tropospheric ducting" or simply "tropo" for short often causes signals to travel much farther than normal line-of-sight distances. How much farther depends on the conditions causing it and on the band you're using. On 2m especially, as well as on 440, signals caught up in a temperature inversion can be carried for a few hundred miles easily. Here in the Buffalo area I have personally worked a ham in the Cleveland, Ohio area who was getting into a local 440 repeater in Buffalo, and the guy in Cleveland was standing in his kitchen with a 5-watt HT. On 6m it's not unusual for tropo ducting to extend several hundred miles.        The 6m band is also subject to E-layer "skip" from time to time. E-skip is one of the propagation methods that the HF bands are subject to. On 6m this makes it possible to work anybody anywhere if conditions are right. A few years back, one of the clubs I'm a member of bought an Icom 706MKIIG, which covers 6 meters. The first contact made using that radio was with a station in California (we're clear across the continent in New York, remember)...enabling us to conclude that (1) the radio works, and (2) the 6m band was "open" at the time with E-layer propagation. I've personally sat at the 6m station during Field Day and worked stations all over the southeastern U.S. racking up contacts with Florida, the Carolinas, Georgia, Alabama, Louisiana, Mississippi - until we had over 100 contacts on 6m SSB phone! The same radio connected to a triband vertical at the regular club station let us work several stations in the northwestern US and southwestern Canada during a 6m band opening that we became aware of upon noticing that we were getting armchair copy of a beacon station up in British Columbia - a mere few thousand miles away from where we were sitting at the time. They don't call 6m the Magic Band for no reason. If your license class limits you to VHF/UHF only and you really want to work distant stations, then 6m is the place for you to be.

Talk Is Cheap, But...

Beyond just picking up a microphone and talking, there are other things you can do on the VHF/UHF bands. If you're in the mood to make some CW contacts, you'll find some CW activity on 6m and sometimes on 2m as well when the bands are open for weak-signal work. There is also digital operating - packet on 2m and 440, and APRS on 2m, and in some areas there are guys doing SSTV as well. There's also no reason why hams couldn't use PSK31 in the weak-signal portions of these bands. On 440 there is also ATV (Amateur television) to be enjoyed. The best way to find out about local interest in operating these modes is to find your local ham radio club and go from there. The point is, there is more to the VHF/UHF bands than just FM repeaters and simplex. Here in western NY there's even a 2m AM club that has a regularly scheduled net where they operate on 2m in the AM mode!

Satellites: Repeaters In Space

Recalling our theoretical discussion of line-of-sight distances based on antenna height above ground, suppose your antenna was so high up that it was actually out in space somewhere, literally miles above the earth. You'd expect to get some incredible range wouldn't you? Except that the transmission line loss at these frequencies would make it impossible to get the signal up to the antenna, and the coax would be a hazard to aviation anyway.        Fortunately for us, there has since the early 1960's been a program called OSCAR (Orbital Satellite Carrying Amateur Radio) that involves putting ham radio stations in space aboard satellites. The first of these satellites was very basic, it sent HI in Morse code on one frequency and that's all, but guys back then had a lot of fun trying to catch it as it zoomed overhead.        Today's OSCAR birds are much more sophisticated, of course. Some have fully functional FM repeaters aboard. Others have digital store-and-forward capabilities that let you do file transfers with another station halfway around the world if you are so inclined. Check the AmSat website for more information on satellite operating. There's also a chapter in the ARRL Handbook as well as entire books dedicated to the subject. Or, again, find your local ham radio club and you'll likely have a chance to converse with one or more satellite enthusiasts there. There are even clubs that specialize in satellite operating, just as there are clubs that specialize in repeaters, in DX'ing, and so forth. Clubs are a great resource for hams, so find your local club(s) and get involved!

Finally...

Here's a tip that's primarily for a beginner, although for some reason the underlying premise seems to escape experienced hams as well from time to time.        If you trouble yourself to do the math you will find that a 5/8-wave 2m antenna happens to be a 1/4-wave at 6 meters! Thus a 5/8-wave 2m antenna can serve as a 6m antenna as well. This is one reason why I bought a 5/8-wave 2m ground plane a few years back, rather than a 1/4-wave 2m GP. You'd be surprised how often guys who have a 6m antenna think they don't.        Also, those magnet-mount RadioShack scanner antennas can also transmit on 6m, 2m, and 440 - they won't give you any gain but they will work, assuming you take the time to adjust them properly...giving you a mobile antenna in a pinch.        Hope to hear you on the VHF/UHF bands soon!