Wednesday, January 14, 2009

VHF Contest School: Antennas

(by Todd Sprinkmann, KC9BQA)

Experienced VHF/UHF hams will tell you that the antennas are easily the most important of your station. They are right. Every single decibel is precious. This is not like HF where you can throw up a random wire and often work DX. From how high you get your antenna, to how much antenna you can afford to put up, right down to the feedline you use... it all adds up.

Feedline is so much more important than it is on HF. The dB losses at higher frequencies become much greater. There are better feedline experts than I, but if you have junk coax and you're trying to work weak ones on VHF, you're shooting yourself in the foot. Honestly, sometimes just improving old or lossy coax can really make a big difference in what you hear and work. If you know your coax is cheap or old, spend a few bucks and get something thicker and better.

On VHF/UHF get your antennas as high as you safely can. Just getting an antenna 10 or 20' higher can make a huge difference. Or maybe getting it above a tree. Or stepping up to a 7, 9 or 11 element beam, instead of a 3 or 5 element.

If you have a poor QTH, try getting out in your car and driving to a location that's high up. Operating contests as a rover is a lot of fun. For some VHF'ers that live in places with antenna restrictions, apartments, roving is how they really have fun in contests. I love rovers just about more than my antennas! (Look for my article entitled ROVERS when I get around to typing it up.)

I'm gearing these articles toward beginners, so don't get too concerned that you aren't able to have stacked yagis up 100', OK? Put up the most antenna you can, get it as high as you can, have good coax, get on the air and start having fun. But if you want to know more about antennas on 2 meters, or 6 meters, read on.

I found some links to a ton of antenna projects for you homebrewers. Here's a lot of food for thought: Make sure to scroll down that page a little bit, and you'll see antennas not only for 6 meters, but 2 meters and higher. Happy building! In fact, that whole site is amazing.

For best results in a contest, as well as general VHF hamming, you want to have antennas that are both horizontal and vertical polarization. Horizontal so you can work the SSB stations and vertical for the FM'ers.

This may not be practical, but a lot of guys do have multiple antennas for at least 2 meters, and quite possibly 6 meters and 70 cm as well. If you are a beginner, do keep in mind that you will work some stations even if your antennas are cross-polarized (with the corresponding 20 dB reduction in signal strength). Any contact is a good contact. So don't get too hung up about polarity as a beginner.

We have had some guys check into the nets on SSB, with verticals. They aren't terribly strong, but they're being heard and enjoying the hobby. And if I hear them answer my CQ Contest, I'm not concerned about what polarity they are. I just take the contact, thankyouverymuch. :) An S1 contact in a contest counts just as much as an S9 one.

Just know that if possible, adding some horizontal antennas and being able to work SSB will get you lots more distant stations in your log. SSB is the predominant mode in VHF/UHF contests.

Making a horizontal loop for a given band is a very cost-effective way to start discovering how far you can work on SSB. Plan on having this capability for the summer months, if you don't have the time to get one made by next weekend.

Another consideration is whether you want to have a beam antenna. If you do, you'll definitely work farther when you're pointed at someone. Thing is, though, sometimes you want omni-directional capability. Having both options is a bonus.

Since this is for beginners, I will wrap things up here. The antenna building projects will get you thinking.

But if you're new to contesting and you're wondering how well your station gets out, a VHF/UHF contest is the single best time to gauge what you can do. The sheer number of stations on the bands is larger than at any other time.


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