One young lady I was talking to recently made reference to the two bands that hams are using these days. Being more confused than usual, I asked which two bands she was talking about. I was told that the two bands were HF and VHF. Oversimplication to be sure but in a couple of areas, it is a very appropriate visualization.

HF: Large antennas, long distance communications, direct communications, high power is common.
VHF: Small antennas, short range communications, repeaters, low power is common.

Yes I know, these are generalizations but, fairly accurate. A lot of hams spend a lot of time on VHF/UHF these days though. And it is not just Technicians. What draws them? Actually a lot of things, like Packet Radio, DX Clusters, Moon bounce, Satellite communications but most of all, repeaters.

VHF is primarily a line-of-sight band of frequencies so your antenna height and power play a significant role in how far away you can communicate with another station. There is no substitute for a nice high antenna and a lot of power. If you could take your handheld radio up in an aircraft to around 10,000 feet, you would find yourself with a 3 state range, even with only a couple of watts.

That's what a repeater does for you. OK, here's the REALLY basic description of a repeater. At the top of a building there is a receiver on 146.31 MHZ and a transmitter on 146.91 MHZ. We have connected the speaker leads of the receiver to the mike input of the transmitter (this is very crude and not the best way to do it so "Kids, don't try this at home") and added one other piece of equipment. A little device called a carrier operated relay or COR for short. The COR is connected to the receiver and when a carrier is detected by the receiver it causes the COR to key the transmitter. Modern VHF/UHF transceivers automatically are set to provide an automatic switch between transmit and receive frequencies, so when vehicle "A" sends a signal out on 146.31, the repeater hears it and then retransmits the audio on 146.91 so vehicle "B" can hear it. What is so great about this is that vehicle "A" and vehicle "B" can talk to one another over a much greater distance than they could if they were trying to communicate directly to one another. Because of the greater height, the higher power and the much better antenna at the repeater site, the receiving and transmitting range is far superior to any mobile. And anything the repeater hears, it retransmits. A handheld radio suddenly has a range equal or better than most base stations or mobiles. A mobile radio becomes very powerful.

When you are finished talking and release the mic button, the VHF/UHF transceiver switches over to 146.91 receive so that you can hear the output from the repeater. When you push the mike button to talk, the transceiver again goes to 146.31 transmit.

Repeaters have been placed on tall buildings, towers, mountain tops and water towers. Anywhere where the repeater operator can get a height advantage. Oh those mountain top repeaters! I have heard of some that provide as much as 150 mile range or more for a mobile radio.

So how do you use a repeater? Because a repeater is most often a local device, there tend to be a lot of answers to this question. I will try to stay with generalities.

Repeaters operate on repeater frequency pairs. Those are the receive and transmit frequencies I mentioned before. In most areas of the country repeaters make use of a suggested Band Plan originally formulated to bring some kind of regulation to repeaters so that hams travelling through an area have a reasonable chance of communicating with other hams in the area. There are a few repeaters in some parts of the country that have not adheared to the Band Plan so you should contact the local hams to find out about local operations. Some common repeater pairs are: .34-.94, .28-.88, .16-.76, .04-.64. And many more in just the two meter band. When you get your first VHF or UHF radio, always purchase a Repeater Directory at the same time. It will answer most of your questions about frequency and tone

As repeaters become more common, many repeaters are going to tone access to prevent more than one repeater from being keyed at one time. Tone access means that your transceiver transmits a subaudible tone and the repeater will not key unless the tone is present. There are many diffferent tones available so you will need to know what frequency tone is being used in your area.

You also need to know whether the repeater is "open" or "closed". Most repeaters are "open" and while a club or individual may have expended a great deal of money on the project, it is there for any ham radio operator to use. There are however a few "closed" repeaters and it is always nice to know ahead of time when a "machine" (repeater) is restricted to club members only.

Now then. What do you actually say on a repeater? Again there are local variations. In most areas of the country I have been in, you announce your presence on the machine by just saying your call sign. Just "K9RWE". That's it. Because the machine retransmits you, it isn't neccessary to go through a long "CQ CQ CQ, this is K9RWE etc" kind of thing. Also, because it is an FM mode, is very easily understood and the people using it are generally local, most repeater operation is done in short conversational transmissions. It does not emulate the HF style of long transmissions followed by someone else doing a 10 minute monologue. Repeater conversation tends to be more like a telephone conversation only with push-to-talk buttons.

Conversations cover the whole gamut of subjects much like any other mode of ham radio but seem to have more local focus. Many repeater groups are heavily involved in community support with weather watch nets, emergency communications during power outages and providing volunteer communications for parades, fund raising walks, bike rides and other similar functions that lend themselves to the short range very reliable communications provided by FM VHF/UHF repeaters.

On top of that, it is a wonderful way to keep track of what everyone in the area is doing including what club meetings are coming up and who's going to the hamfest next week. Around here, one of the repeaters puts on several nets during the week including a computer net which helps provide answers to persons having a little problem with their computer, a swap net for hams trying to get rid of gear they no longer need, and a net on Saturday night that presents a subject to those operators who check in and then everyone has an opportunity to comment on the subject. The topics are varied and provide some really lively exchanges of ideas!

So, that's the (very) short and (very) simplified explanation of repeaters. The same concepts apply to repeaters no matter which band they are on, 50 MHz, 144 MHz, 220MHz or 440 MHz or anything else. The frequencies and frequency splits may be bit different, but basic operation is the same. Have fun on the repeater in your area and be kind to other users. Always listen between transmissions for others who may want to get into the machine too.

 

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