VHF/UHF/Microwave Equipment & Operation

(A technical talk given at the MVARA on 1/10/08)



When Jerry,W8JV asked me to do a talk on VHF, I wasn't really sure what all I wanted to cover, or how I was going to do it. Then on one of the microwave email reflectors, the question as to the best way to get on microwave with the least amount of cost. This question was asked by 14 year old ham who was active on HF 80-10 meters. Since I'm guessing that almost everyone here is active on the HF bands, this might be a good way to approach this forum.

Of course the emails that followed, for the most part dealt with various microwave transverters, the pros and cons of each, until one brave soul stepped out of line and made this statement:

"You need to crawl before you walk before you run. My suggestion to ALL the new hams I talk to is to start with one of the all band all mode rigs.

I am partial to the Yaesu 857/897 myself but there are others. With one of those you can work 50, 144 and 432 MHz as well as HF. They have enough power on 6 and 2 that you can get by without A TX PA for a while. Cut your teeth on those bands first and then when you decide you are ready to go higher in frequency you have a nice IF rig to use with transverters."

So, lets talk about this for a moment. How many of you have ever operated 2 meter SSB? If you haven't, you dont know what youre missing.

Two meter SSB is a lot different than FM, as the range is much farther, and with simple equipment, its easy to work over a couple hundred mile range under normal conditions. Many of the propagation modes that one uses to work over the horizon microwave also begins to occur on 2 meters.

There is much to be learned by operating 2 meter SSB, but there are other very good reasons for the fellow who wrote that email to say what he did. First off, most if not all microwave contacts are coordinated via 2 meter SSB. Therefore you almost need to be capable of operating 2 meters anyway, so if you arent on 2, that's the place to start.

OK, so since we're talking about 2 meters for the moment, lets explore what it takes to get on 2 meter SSB. Many of today's lower priced HF rigs have 2 meters included with them. Like the above email author, I too am partial to the Yaesu line.

Icom makes a couple rigs too that have 2 meter SSB, and I also believe Kenwood has a rig or 2 also. I built my station on a budget, and I found the Yaesu rigs have the most bang for the buck when it comes to VHF. The Yaesu FT-817ND is a QRP rig that covers HF, 6, 2 and 432. It outputs anywhere between ½ watt – 5watts on all modes on all bands. The price tag is about $600. This is actually a good entry level rig, and you will be surprised what you can do with 5 watts into a reasonable antenna.

Another rig that is worth looking at is the FT-857D or the 897. There isnt a lot of difference between these 2 radios. They both do 100 watts on 160-6 meters, 50 watts on 2 meters and 20 watts on 432. This is what I currently use on 2 and 432 now. Yaesu is the only brand that I'm aware of that includes 432 mhz in their HF rigs.

Now that we covered the rigs, lets talk about antennas.

I home brew my own VHF antennas. I did it really on the cheap, and saved probably 75% of the cost of a commercial antenna. If you want to buy an antenna, M2 (M Squared) makes probably the best antennas on the market, but you'll pay dearly for one. Cushcraft makes decent 2 meter antennas as well, as well as Directive Systems, and a few other manufacturers.

Lets consider what it takes to build your own beam. Back in the mid to late 80's a fellow by the callsign of K1FO designed a yagi that is easily duplicated, can be built with any number of elements over 9 elements, has a pretty clean pattern and has good performance. I built a 10 element yagi using his design, and have done well with it, regularly working the east coast and to indiana and illinois to the west. I used square tubing which I purchased from a fence company in Struthers. The elements are made of ¼ inch solid rod which can be had on the cheap from Star Supply. They also have boom material as well.

Total cost was probably around $30. The hardest part was the driven element. It uses a TEE match, which consists of 2 matching arms on either side of the boom, and a half wave coaxial balun. Not real difficult to make, but there is more work involved with the driven element. Of course one can also gamma match the driven element, but the performance wont be as good. This antenna works so well that a number of stations think of me as a "big gun" on 2 meters, but in all actuality, I'm just running an average 2 meter station. Again, I did it on the cheap,and its not hard to build your own beam.

Older handbooks have some good designs,as well as the internet. OK, now you're on 2 meters, you've operated the band for awhile, and now you want to try the next higher band. You're running one of the Yaesu rigs mentioned above. To get on 432,now you only need another antenna.

Hey, guess what... K1FO designed a 432 version as well! When you go to build your 432 antenna, you'll quickly find out that a 432 antenna is alot smaller than a 2 meter antenna. Because 432 is 3 times the frequency of 2 meters, the antenna is 1/3 the size! I'm going to let you all in on a little secret at this point however....Don't build a 10 element beam for 432! Take advantage of the small size and build a bigger beam! You can fit 22 elements on a 12 foot boom.

Take advantage of that, and build your 432 beam as big as your 2 meter one. The elements are only about a foot long, but you can put a lot more elements on the same boom length. Take my word for it, you will need the additional gain. Also, use the very best coaxial cable that you can afford on 432. Belden 9913 is the bare minimum for 100 foot or so long runs, half inch heliax is better. You CAN notice a difference!, OK, now you're on 432 as well as 2 meters.

What should you expect? Well, first off, there are about half as many stations equipped with 432 as there are on 2 meters. Signals are typically a bit weaker on 432 than they are on 2 meters, but the noise is lower, and you can copy weaker stations on 432. The weaker signals on 432 is the reason I suggest building a bigger beam for 432. With my station, I typically can work about 90% of the stations on 432 that I can on 2 meters. Heavy tree cover, dense trees near the antenna will attenuate the signals on 432.

I have a large tree to the north of my antenna, and I have trouble working into Michigan because of it, but to the East, the trees are less, and farther away, and I work in that direction much better. Same way with the West. South isnt too bad, but East and West are my best directions. I skipped the 222 mhz band, only because I'm not active there and I have no experience on that band. From what I'm told however, 222 is actually better than 2 meters.

Propagation is basically the same as 2 meters, but with much less noise.The next amateur band is the902 Mhz band. I do not have equipment for that band either. Instead, as I started moving up the bands, I elected to try 1296 Mhz. This is the 23 cm band, and is considered to be the lowest microwave band. To get on these bands, one needs a QRP rig. This is why I suggest the Yaesu FT-817 as a starter rig. You can use it as a driver for a 1296 and up transverter.

All the bands above 432 will be run using a transverter although there are a few all mode 1296 capable rigs. They are rather expensive, however. I run the Down East Microwave transverter. Although mine is about 10 – 15 years old, they have newer versions that run more power output than mine. 1296 has many of the qualities that 432 has except that about ¼ of the stations that are on 432 have 1296 capability. Signals on 1296 are a level weaker than on 432, which means that more antenna is needed to be successful on that band.

You can fit 45 elements on a 12 foot boom on that band. I would advise stacking 2 of these antennas to help bring in signals. Trees kill the signals on 1296 a LOT more than they do on 432, so your antenna really needs to be in the clear. 1296 is truly a microwave band. The signals are line of sight, literally, unless there is some tropo going on, and even if there is, if your antenna is surrounded by trees, you wont have much luck. Feedline becomes really critical up here.

You will lose 20% of your power when you use 100 feet of 7/8 heliax, so a lot of operators like to place the transverter in a weatherproof box and place it up near the antenna to avoid line losses. I'll be honest, I havent had much luck on 1296. It is a very difficult band to make work successfully. It's handy to know someone with test equipment capable of checking microwave gear when setting up on this band. SWR meters that are common dont work well this high a frequency.

SWR can be checked with special devices called "directional couplers" which can sometimes be found on ebay at reasonable prices, but they are not as easy to use as your every day SWR bridge.T his band may be much better if operated portable, and at the time this is being written, I havent tried this yet. Dish antennas also begin to become useable on this band if they are of a rather large size. By large, I mean 6 feet in diameter or larger.

Now, lets talk a little bit about Dish antennas....There is this rumor that says the higher you go in frequency, the weaker the signals become,and so far this APPEARS to be true. You would think, why would we want to go higher if the range is less, and the signals are weaker ? Well, once you get into the microwave bands,something very interesting happens. Especially when we work with Dish or Horn antennas.

It is true that the path losses are higher as you go up in frequency. They increase 6 dB everytime you double the frequency. Therefore, if the GAIN of an antenna is the same on 1296 asit is on 432, the signalwill be about 6-8 dB weaker. You must double the boom length to increase your antenna gain 3 dB on a yagi. Therefore, you will need 4 times the boom length to equal the signal strength on 1296 as you would on 432.If you use a dish, something strange begins to happen....Lets say you have a dish on 1296.

Your dish, for the sake of this argument has a gain of 20 dB. The other station you are working has the same antenna you do. What happens if, lets say you double the frequency,and move up to our next amateur band, 2304 Mhz? Well, dish antennas are broad band antennas. The feed will have to be changed, but the same dish can be used. What happens to the gainas the frequency is doubled? The gain increases 6dB. Interesting! Since the path losses increase by 6 dB as the frequency is doubled, and both you and the station you are working both use the same antenna that youworked on 1296, the combined increase in gain is 12 db.

Therefore, the signal strength actually INCREASED by 6dB, or about 1 S-unit. That blows that theory out of the water, that says that as frequency is increased, the signals get weaker, huh. Well, thats not quite the case. The physical law actually states that if the GAIN of the antennas used are the same,then the signal strength will drop 6dB as the frequency is doubled.

This is not what happened however. So lets go with the law saying that The signals will INCREASE in strength and the SIZE of the antenna remains the same. OK, lets carry this up to the 10 Ghz band. I can speak from personal experience here by saying that signals on 10 Ghz will out-perform a 2 meter signal over a given path, if you operate your station from a good location, meaning no trees, and in the clear. I set up on the shore of Lake Erie. I have a 2 meter station set up also. I use a small 4 element beam on 2 meters. I make a contact with someone in Michigan, who is about 200km away.

His 2 meter signal is running about an S-2 – S3. I'm running 50 watts, and he reports a similar signal strength on his end. What should we expect our report to be on 10ghz with a tiny 2 foot dish on both ends and 1/5 of a watt ? Would we even hear each other? Well, my first time out, I thought... geez these conditions are horrible! there's NO way! But of course I had to try anyway. I crank the volume up on the 10 Ghz rig all the way up, put myear next to the speaker, and wait for him to call.

As I tune across him, and my head BANGS against the tripod, almost knocking the dish over as his 30 over signal causes temporary hearing loss in my left ear as his voice comes screaming in, almost overloading the receiver. Taking a few minutes to recover, I sit there and have a short ragchew with NE8I in Sterling Park, Michigan with steady, non-fading very strong signals. I sign with him, and another station calls me, this time another 100 km farther inland in Michigan calls with a 20 oversignal. We ragchew for about 10 minutes never missing a syllable. All of a sudden, someone directly across the lake in VE3 land calls. Now this fellow is only about 65 miles away.

This dude is literally buring the S-meter at 40 over, and this time he is a little difficult to copy, because he is overloading the receiver to the point of distortion. This is with 200 milliwatts into a 2 foot dish. So you see, on 10 Ghz, the signals run roughly 40 db stronger than on 2 meters, even though I'm running 200 times more power on 2 meters with an antenna twice the size. On top of that, on 10 Ghz, you only need 5 grid squares to get a VUCC award, where as on 2 meters,you need 100 Grids. So you tell me, which band is harder to become a big gun on? I got my VUCC on 10 Ghz, but im not even halfway there on 2 meters.

There are other propagation modes on 10 Ghz other than the un-obstructed path tropo like I worked on 10 Ghz across lake erie. The next most popular mode is "Rain Scatter". Although this dosen't happen on 2 meters, it is a pretty reliable mode on 10 Ghz and up. The idea is to have both stations aim their dishes toward VERY intense rainfall somewhere between the paths of the 2 stations. Contacts occur regularly over 300-400 mile paths, and in the heat of the summer, contacts occur 600-700 miles at times.

Snow storms too will cause the same effect, but over shorter distances, because a snow cloud isnt as high above the surface, but distances are still made 2-00 – 300 miles out. A tad bit more power is needed to use this mode, but not a lot more, on the order of 2 watts is what the average operator uses on 10Ghz to work the rain scatter modes. Just think, all this running QRP!