DSC VHF and Voice VHF radio range

[rogerthebodger]

Following on from the radio range out safety authority consider that the range of a VHF DSC radio call range is larger than a voice only VHF radio call.

Ignoring any, atmospheric conditions, I cannot see how there can be significant difference in range as both are line of sight and both ch 80 and ch 16 carrier frequencies are very
close.

Any one have any proof that the range of a VHF DSC call is significant greater than a VHF voice call.

 

[prv]

It's not that the radio waves travel further, but that the digital signal processing in the DSC receiver is better at making sense of a broken signal at extreme range than your ears are.

I don't know how significant the effect is, but it's certainly plausible.

Pete

 

[TernVI]

Seems quite beleivable that the digital calling will be low bandwidth, so will operate to a much lower signal power.
The way the messaging is handled is probably also a lot more ribust than hoping a human operator understands what's said.
I don't know about your coastguard, but ours has a number of remote receiving stations which would presumably automatically deal with a distress call. As would any ships.

 

[RichardS]

It's not that the radio waves travel further, but that the digital signal processing in the DSC receiver is better at making sense of a broken signal at extreme range than your ears are.

I don't know how significant the effect is, but it's certainly plausible.

Pete

It's the same digital processing effect with AIS which should, in theory be the same as VHF but, in practice, is much longer range.

Richard

 

[GHA]

It's not that the radio waves travel further, but that the digital signal processing in the DSC receiver is better at making sense of a broken signal at extreme range than your ears are.

I don't know how significant the effect is, but it's certainly plausible.

Pete

There will no doubt be some papers published somewhere on google. On ham radio other digital modes will get decoded when you can't really hear or see much of the signal.

 

[AntarcticPilot]

It's not that the radio waves travel further, but that the digital signal processing in the DSC receiver is better at making sense of a broken signal at extreme range than your ears are.

I don't know how significant the effect is, but it's certainly plausible.

Pete

Yes, Basically, you can think of it like this. A digital signal has two values, which represent 0 or 1. They are distinct, and so can be detected using clever filtering and electronics without much difficulty even when the signal to noise ratio (SNR) is very poor. However, a voice transmission uses a very wide range of values, and the SNR must be much higher in order for the voice to be readable.

For the same reason, Morse code is often readable at much greater distances than a voice call - a good reason for learning Morse. Sadly this is an occasion when I haven't taken my own advice - I only know a few characters of Morse!

Of course the voice part of a DSC call is exactly the same as a call connected by the usual channel 16 technique; it's only the initial contact and channel negotiation that DSC automates. But for a distress call, where the essential information is encoded in the DSC signal, that may be sufficient information.

 

[rogerthebodger]

So it seems to have a greater effective range even through the theoretical range is the same.

It seems that this is due to the ability for the electronics to determine what a digital message is better than Mk1 ear.

Our authorities are in the process at installing relay stations around the coast but this like a lot of other government projects delayed with completion dates being pushed back all the time.