C4fm 4 sota

Digital VHF is the main topic of conversation in our radio club. Horses for courses but if you use the internet bridge devices as part of the QSO then it doesn’t interest me personally.
Glad your new rig worked.
So on a digital topic I could get behind. You used fusion to activate the hill, so obviously it wasn’t using repeaters etc. Does the digital aspect, improve the distance covered with your signal? Or just improved the audio quality? I would think if it’s narrower than normal FM voice then it could be advantageous to have the option on a summit?

I have a Yaesu FT2DE which has C4FM capabilities builtin;
NO, I did not buy this radio, I won it a raffle at GMDX Convention a couple of years ago.
I have used the FM and APRS facilities, but the Fusion capabilities are largely unused. There does not appear to be any Fusion activity within the local Edinburgh - East of Scotland.
There is supposed to be a Fusion repeater about a mile away from me, GB7DE, but to date I have only heard 1 station through it; the repeater keeper, and at present this repeater is off the air.
Question: Is there an agreed simplex Calling Freq for C4FM? The use of the FM Calling Freq of 145.500 MHz doesn’t appear appropriate somehow?
Ken - GM0AXY

It’s the same for me. The technical aspect of such linking and trunking is interesting as a problem to solve and to keep running, but using them as the end purpose doesn’t float my boat.

That is £64,000 question. It depends on the modulation scheme, the vocoder and the protocol.

The modulation scheme (4FSK or GMSK) will let you calculate a BER (bit error rate) for a given signal strength. The vocoder data contains voice data and FEC (forward error correction) data. You can use the FEC to fix errors in the received voice data. The protocol lets you calculate how well the receiver stays sychronised and how quickly it can regain sync.

Wide mode Fusion uses twice the bandwith than D-STAR so it can transmit twice as many bits of data and send a higher quality voice signal for the same coverage. DMR fits 2 signals into the same bandwidth as wide Fusion. So you either lower quality voice and lower performance with weaker signals.

Both DMR and Fusion protocols have improved massively on sync performance and recoverabilty over D-STAR, an advatange of coming after D-STAR was in the field demonstrating sync issues!

Simulations and tests suggest a 4FSK signal in a 6.25kHz BW has the same performance as narrow band analog FM in a 12.5kHZ channel.

Fusion clg is 144.6125 - which is where I’m going right now!

Thanks for that; but you need to up your power and aerial in order that I might hear you here in Edinburgh, hi!

It’s actually the calling frequency for all digital voice modes (Fusion, d-Star, DMR)

Interesting to read about your experiences so far Tom. I’ve dabbled with d-Star on a couple of hills, but never heard anyone else on simplex. Like you I’ve had issues getting the radio to talk to my computer (too little free time to spend faffing around on computers - I just want it to work; or, more often, give up and don’t use the full potential:exploding_head: KISS rules).
APRS is another area that doesn’t seem to be used to full potential in the UK.
Is anyone active in the 146-147 band (UK NoV required)?

Okay interesting information.
Looking at the bandplan my impression was that 145.375 MHz would be correct for C4FM


145.375 digital voice calling

But always good to learn something new.

73 Joe

You’re correct Joe. Most IARU 1 countries use 145.375. The UK is different (in so many ways :face_with_monocle:)

UK UHF repeaters input/outputs are designed to cooperate with UHF repeaters in Europe such as PA/ON so the 1.6MHz shifts are reversed. I’ve not looked to see what the 7.6MHz shifts look like.

The UK bandplan does clearly say

144.6125 MHz  UK Digital Voice (DV) calling (Note 9)

and note (9) says

 	Note 9: In other countries IARU Region-1 recommend 145.375 MHz

There is probably a good reason for it being specified like this.

(Usual words needed about bandplans, not mandatory, essentially a good idea, do your own thing etc.)

Yep. That’s where I got my information from too.

I just looked at the bandplan and it gives 145.375 as digital voice calling, so perhaps not so different. If digital voice (of any flavour) brings activity to the wasteland that 2m usually is around here I’m all for it - when there is a consensus mode I will even equip myself with it! :wink:

But which one? There are plenty to choose from.

And there in lies the crux of the problem Brian! I think most people who make the jump do so mainly on the basis of which system dominates nearest to them.
I read up about fusion after reading this thread; and do like the sound of a couple of the features for SOTA. If we agreed on a standard Group ID setting, the radio could alert you to another activator within range. (Sadly I’m not on fusion though :cry:

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There’s been some work lately to bridge the 3 modes. Depends on your local network but I’ve seen a few where you can hit your respective YSF/DStar/DMR repeater and then they inter-op on the backend for the same talkgroup regardless of digital mode.

The only tricky bit is that most repeaters only have specific talkgroups “always on” so you’d want to run a local spot if you wanted to hear it 24/7.

The only trouble with this bridging is that repeaters are not permitted for SOTA. I’ll keep my pockets well fastened until the majority use one DV mode for simplex!

Dose!nt float my boat either looks like another White elephant they come and go these gimmicks Geoff



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I think the goal was to spot on a common talk group, obviously repeaters are out of band for activations.

Considering most of the commercial stuff (DMR, P25) is heading this way due to narrowband restrictions(FCC mandates all new non-ham modes use 12.5kHz bandwidth in the US) I don’t think you’ll see them go away anytime soon. Even moreso as cheap DMR radios($70) are starting to pop up.

Just because it doesn’t do anything for you doesn’t mean you need to talk down to it. As someone who comes from the software side of the worlds I find all of the digital modes pretty fascinating.