Friday, 26 March 2021

REPEATERS FOR BEGINNERS

BASIC  UNDERSTANDING
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.

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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.

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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.
 
WHERE ARE MY REPEATERS??

To find your local repeaters (in the UK) you simply need to visit the RSGB REPEATER LIST and do some sorting...



First thing to do is to enter your 6-figure LOCATOR reference and click on Calculate. Now you need to sort the list by clicking on the km column (or mi column if you've changed to miles).

You will be presented with a list of repeaters in your general locality and beyond. Everything that you need to know in order to program your radio is shown on that screen including the CallSign of the Repeater, its distance from you, the TX/RX frequencies, the Tone and the modes of operation.

I recommend that you program in quite a few - you'll be surprised at how many can be opened from your QTH even though you may think they're too far away. As I said previously, I can open one 40 miles away very easily on 10W. On the other hand, there's some much closer that I can't reach.

Obviously, don't bother putting in repeaters which will only function on modes which you don't have (such as DMR if you don't have a DMR radio).
 

SIMPLEX GATEWAYS

In addition to Repeaters, you will also be surrounded (to one extent or another) by Simplex Gateways. In order to see a list of them, just CLICK HERE and enter your 6-digit locator and do a sort again.


These are usually Nodes operated by individuals with a special licence. The one closest to my QTH  (MB6HW) is operated by my friend Bill (G4CFP) and he usually has his Fusion gateway connected to the North West Fusion Group room, so when I listen to his simplex frequency of 144.8625MHz, I hear whoever is operating in that room. 

If I wish to, I can (through my radio's Wires-X system) change rooms, eg: move from NWFG to CQUK, but before I leave the gateway it is good etiquette to move the gateway back how you found it.

Simplex Gateways are still something that I'm learning about, so I'll leave it there for now until I feel confident to write more about it. Just bear in mind that it costs nothing to tune in to your local Gateways and have a listen around and ask questions. And always leave a 3 or 4 second pause between overs on a Simplex Gateway!

You should also bear in mind that you may find yourself tuning into a nearby Gateway Frequency and chatting away with someone believing that you're going through the gateway when you are actually just talking to someone via a Simplex connection. This can lead to confusion and can also be quite annoying and disruptive to the Gateway.

Imagine for a moment that you are tuned to your local gateway frequency of 144.8625 and someone you normally hear on there is active and responds to your call. He is operator A in the diagram below and you are operator B.


Your handheld's low power signal is reaching your mate's radio, but not reaching the Gateway. Your mate is close enough to you to hear your signal AND he's close enough to reach the Gateway....


So he's you're both happily chatting away to one another but your mate is also chatting on the Gateway, so any Gateway listeners can hear all your mate's side of the conversation, but none of yours. This is the Simplex Conundrum and you need to be mindful of this when transmitting on a nearby Gateway frequency.

So how do you know if you're both getting through to the Gateway for sure?? Well I guess that you could both call for a radio check and see if someone nowhere near the locality is hearing you both - that way you know for sure that you're going through it. There may be better ways, I'm not sure, but I'll update this page when I find out more.

Your local radio club should be your first port of call for learning about these things, so do ask around at the club for further guidance.

UPDATE : My friend Bill (G4CFP) has pointed out that you could always press your DX button to connect the Gateway to WiresX to confirm that you are actually reaching the gateway. He further points out though, that some repeater/gateways are locked to particular rooms and won't allow you to alter the room.

Take care, 73, Tom, M7MCQ.

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