So you bought your very own Ham Radio! Now what? Well I’ll go over the Ham Radio Basics: Simplex VS Repeaters and using a 2m / 70cm (440) Ham Radio. There are two basic ways to communicate using your new radio. One is what is called Simplex. The other, more popular way, is using a Duplex Repeater. It may sound complicated, but relax, I’ll make it simple for you to understand. For those of you that already have your Amateur Radio License, this should be a review. But I will break it down anyway for the benefit of those who don’t.
When two or more stations contact each other using the same frequency for both transmit and receive, they are said to be operating simplex. So what does that mean? Remember using walkie-talkies as a kid? Do you use FRS or GMRS radios? That is all simplex.
I hate referring to a CB, but that is also Simplex Communication Basically, you and the person or persons you are talking to are all set to the same frequency. You have to wait for the other to finish talking and release the microphone button before you take your turn transmitting. And, you are also transmitting directly from your radio to the receiving radio(s).
This is where one station transmits on frequency A and receives on frequency B and the other station transmits on frequency B and receives on frequency A. This one gets a bit more involved. “Duplex” gets broken down again into two parts Full Duplex, and Half Duplex.
- Full Duplex: While not “exactly” correct, the best way to make it simple to understand is to think of a telephone. Imagine the earpiece of your phone connected to the microphone part of another phone, and that phones earpiece is connected to the microphone on your phone. You and the person you are talking to can both talk and be heard at the same time. (This is how a Repeater works, more on that later…)
- Half Duplex: Works the same way as Full Duplex, BUT, since your radio can not transmit and receive at the exact same time you still have to wait for the other person to finish transmitting before you can transmit back.
So why in the world would you want to use Duplex at all? It sounds just like a complicated way to do simplex. Well, yes it is. BUT if you want to use a Repeater, you will need to set up duplex.
What is a repeater?
Ok, what is this repeater thing? Well, it is a device consisting of a transmitter and a receiver. It picks up your transmission and simultaneously retransmits it. I know what you’re thinking, What good is that? Well, a Repeater is just a fancy real time relay station. Usually they will have much greater range than you will if transmitting from a handheld or mobile radio. They have large base station or specialized “Repeater antennas” mounted high up in the air. Also Repeaters usually put out much more power than you will be using.
Let’s say you’re using your 5watt handheld which would consistently be able to talk 10 to 15 miles. As long as you are in range of the repeater, it can increase your range to 50, 75, maybe even 100miles.
For example, Let’s say you live 15 miles south of town, your friend lives 15 miles north of town. That is 30 miles between you. Depending on the terrain and elevation, you just might be able to communicate simplex on one of these two bands, but it will definitely have some static on it. Now let’s say that in town there is a Repeater! Now you and your friend only have to get your signals to the repeater, and it will relay your transmissions in real time for you!
OK, before you get too excited, I know I said all you have to do is get your signal to the repeater and it will relay for you. Well, now I have to throw some more “techie” stuff at you. Just because your signal gets to the repeater, that doesn’t mean it will “hear” it. Remember earlier I talked about full duplex? Well this is where that comes in. You’ll need to know three things about the repeater. 1 the output frequency, 2 the shift, 3 the access tone. Let me break that down a bit for you.
- The Output Frequency – This is the frequency your radio will be set to “hear” the repeater.
- The Shift – This is the difference between the output frequency and the input frequency. There is a standard shift amount. For 2m it is .600Mhz (or 6Khz) and for 70cm(440) it is 5Mhz. You also need to know shift direction +up or –down.
- The Access Tone – This is a sub-audible tone also known as CTCSS or PL. The tone is not always used, but if the repeater is programmed for a tone then it will not repeat any signals it receives that do not have a tone on it.
I know, it sounds like a lot of work just to talk on the radio, but once you have it programmed and stored into memory it’s just a matter of selecting that memory channel and you’re on the air.
Where can you find all of this information? It is available from many different locations. The ARRL puts out a book out called the Repeater Directory. There are also a few Android and IPhone Apps. And there are many places on the internet to find this info. Think of a Repeater directory as a phone book for repeaters. Here is a link to the online database I use. http://www.repeaterbook.com/ (they also have a great Android APP, and no I don’t work for them. LOL)
Ok, quiz time!
“You just went to Repeater Book and looked up a repeater near my hometown. Here is the page that came up.”
HINT: The first two are 2m and the last three are 70cm(440)
Q) What is the output frequency of the first one?
A) You should have got 146.625 The displayed frequency is the output frequency.
Q) Ok, what is the input frequency of the first one?
A) You should have got 146.025 Remember 2m is a .600Mhz offset, see the minus after the frequency?
Q) Ok, what is the input frequency of that last one?
A) You should have got 449.725 Remember 70cm(440) is 5Mhz offset, See the + after the frequency?
Q) What is the tone for the last one?
A) That’s right 131.8
Q) What is the tone for the second to the last one?
A) Ok that was a trick question. There isn’t one for this frequency. 😛
Show & Tell Time
Lets say you clicked the second one. The 147.195 N3ETV repeater, this is what you would see… By the way, this is the repeater that my club runs.
This page will give you more details. Notice on the “Features” line it says Autopatch, e-power, linked.
Autopatch means you can (with the right passcode) connect to a telephone line using your radio.
e-power means just that. This repeater runs off of battery power with large solar pannels and a couple small windmills keeping them charged up.
Linked means with a few touch tones it can be connected via radio-waves to a few other repeaters in the area. This increases the effective range of communications. Anyone transmitting through any of the linked repeaters will be heard on all of them. This can be done for many reasons, usually for emergency responses, and training for those emergencies. When linked we can cover most of western PA and parts of Eastern Ohio.
You’ll find most of the 2m and 70cm(440) repeaters are set up for emergency situations. E-power, linking etc. And like the image above says “When all else fails, amateur radio”
Jake McCracken KC3BDF
For more information about Jake and ham radio you can listen to the pod cast we did last week. Or visit The Bug Out Location which is a community of preppers that we put together. Jake is very active there in the “communications” group.