OF VHF/UHF REPEATERS
If you're totally new to all this and have never used a Repeater before, this post may help you a little. Just bear in mind that I'm only an M7 licensee and know next to nothing about anything, but I think I understand the basics, so here goes...
First of all, let's just very quickly explain why we might need to use a repeater in the first place. When you are trying to make a simplex contact with someone who's line of sight is interrupted by high terrain or even tall buildings, you might choose to use a repeater to overcome the obstacles. Most repeaters are located on high ground or in a location which has good line of sight between multiple towns/cities.When you transmit to a Repeater which is within your reach, your signal goes into the repeater on one frequency and is instantaneously re-transmitted on a different frequency. Because of the Repeater's height and location advantage, your re-transmitted signal can now hopefully be heard by your friend on the other side of that hill which was getting in your way.
And it's not just about buildings and terrain blocking your simplex signals - it might just be that your friend cannot hear you simply because you're too far away. Having a Repeater half way between the two of you will often mean that you can successfully make contact.
Each Repeater has a CallSign just like you. They also have an Input (RX) frequency and an Output (TX) frequency. Some Repeaters operate on simple FM Analogue, some on Digital, some Fusion, some DMR and some DSTAR. For now, let's just consider simple FM.
Let's look at GB3EG in Wigan, UK. It's a UHF Repeater located in IO83QN. It has an Output (TX) frequency of 430.9125 and an Input (RX) frequency of 438.5125. So it receives on 438.5125 and re-transmits on 430.9125.
So if you wanted to use GB3EG, you would LISTEN to the repeater transmissions on 430.9125 and you would TRANSMIT to the repeater's receiver on 438.5125.
Just pause and make sure you understand that. This diagram may help...
So from your point of view, you are using two frequencies and it would be a pain in the backside if you had to keep quickly switching between the two during a conversation. Well your radio is capable of operating in SHIFT mode, where you tune into a particular frequency and the radio SHIFTS the frequency by a certain amount while you're pressing the PTT button. Repeaters tend to use common shifts and the one in the example above uses a shift of plus 7.6MHz.
Repeaters are best stored into your radio's memory bank. So with this particular repeater, you would choose FM MODE, tune into 430.9125 and store the frequency in a Memory slot with an alpha-tag of GB3EG (or maybe Wigan) and a Plus 7.6MHz shift.
There's one more thing to do before you save that Memory though!
If you simply transmit to a repeater's input frequency, nothing will happen, because repeaters require you to send them a "TONE" in order to open up their squelch and give you access. All modern radios have these tones stored as a list, so it's just a case of telling your radio which tone to use for this particular repeater.
GB3EG uses a tone of 82.5 so add that setting to the Memory Slot and then Save.
When you go to that memory slot in your radio, it will know to listen on 430.9125 and before transmitting on 438.5125 it will send the correct tone to open up the repeater's squelch.
If you finish programming your radio and the repeater does not respond at all when you key up, just double-check to make sure you didn't get the repeater's TX/RX frequencies the wrong way around in your memory slot.
And bear in mind that even though a repeater is closeby, it doesn't necessarily mean that you can open it. From my own QTH I am unable to open a local repeater 4 miles away and yet I can open one 40 miles away! It all depends on what's between you and the repeater.
So there you have it - a simple analogue FM repeater. How about a Fusion repeater?? Well they're just the same! In fact they're often easier because you don't have to enter a CTCSS tone - you just store the RX/TX frequencies, MODE and the correct SHIFT into a Memory slot. Most Fusion Repeaters are connected to a particular room on Wires-X and if you change that room to another, the repeater will eventually switch itself back to its favoured room. Some of these repeaters are locked to a certain room.
Many repeaters are MultiMode, meaning that they can handle Analogue, DSTAR, DMR, C4FM, etc. If you had a radio which includes FM and DSTAR you might want to program that multi-mode repeater into your radio's memories twice - one slot for working analogue FM and another for working digital DSTAR. Having said that, many modern radios have Automatic Mode Switching.
To test your memory programming, you should see if you are able to 'open' each repeater. When you transmit to a repeater, it should reply with a short beep or a string of morse-code and stay transmitting for a couple of seconds (or someone listening may reply to you).
Repeaters have TIMERS and will automatically shut down after a certain amount of TX time has passed - typically 3 minutes. When in a QSO with someone, it's important between overs to leave a good 3 second gap to give the repeater time to stop transmitting - otherwise your TX-time will be considered as a continuation of your friend's time and will therefore be cut short. If you wait for the repeater to fully stop transmitting before you start, you will get your full 3 minutes to chat.
Before moving onto other aspects of repeaters, it's worth noting that (as with all other Ham Radio operations), a Repeater Etiquette exists.
The basic rules are....
- ALWAYS LISTEN before transmitting!
- Call a particular contact "G4CFP, M7MCQ".
- Don't call CQ!
- You can solicit a call with "M7MCQ listening on GB3BEG"
- Use Phonetics.
- Try not to interrupt an existing conversation unless you think you have something useful to add. You may ask if it's okay to join in.
- Try not to hog the repeater if activity/demand seems high.
- Do not test repeaters by using a short PTT pulse. Instead, say "M7MCQ Testing".
- Leave 3 second pauses between transmissions so that the repeater doesn't time out and so that other people have the chance to 'break in'.
- If you have gone into 'ramble mode' and think you are going to time-out on the repeater, you can say that you're going to take a quick break and stop transmitting for 3 seconds to reset the repeater's timer and give you longer to finish what you were saying.
- BEAR IN MIND that ANYONE could be listening to the repeater output, so don't treat it as some sort of private network! Watch your P's and Q's.
- ALWAYS welcome newcomers and those who sound nervous.
- Be kind and courteous.