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back to article Radio amateurs fret over G.fast interference

As vendors, carriers, politicians, analysts and advocates of all kind queue to offer their support to the emerging G.fast standard, there's one group watching developments with apprehension: radio amateurs. Their worry, as outlined by UK interference-watcher forum Interference.org.uk, is that aside from notches for FM radio and …

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Bronze badge
FAIL

In other words, the current spec only uses frequencies below 106 MHz

That's still MF (160m) though to the low-band VHF (6m) potentially wiped out, which, I dunno, is only the most useful bit of the amateur spectrum.

Not to mention the other HF users out there such as land mobile, marine HF, HF airband, etc…

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Re: In other words, the current spec only uses frequencies below 106 MHz

Just because it currently uses frequencies below 106MHz does not mean that you won't get significant harmonics above there.

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It works both ways, too - not only does the RF electrical signal leak out as electromagnetic waves thanks to the (very) imperfect transmission-line qualities of the local loop, but for the same reason the data signal is susceptible to high field-strength radio signals. There is clever defence against impulse noise (the most common universal source) but a high-power transmitter in your vicinity could well play havoc with the xDSL signals.

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Silver badge

Not a problem for DSL

If the line throws up too many errors it'll reset and redo the training phase and notch out the frequency it is broadcasting because it'll see that range has having too low a SNR.

Transmitters are not really an issue, unless someone is broadcasting a 100 MHz VHF wideband signal down the street.

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Re: Not a problem for DSL

Tell that to everyone who's broadband goes TU once the house next door gets covered with christmas lights and their dodgy controllers..... I guess I should have been a bit more generic about what I meant by "high-powered transmitter".

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No, up to 212 MHz

Unless they are going to also ban most of the spectrum above 108 MHz and below DAB, this is also going to disrupt aircraft radio, ILS and navaids

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Bronze badge

Re: No, up to 212 MHz

That seems pretty unlikely - the power levels involved are very low - they have to be to allow this stuff to work without the crosstalk from one circuit killing every other service running on the cable. I suspect the very deliberate propagation characteristics of airborne / land to air radio services might also protect against interference.

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Mushroom

Ah, well back to the drawing board

It's about time to design a working portable EMP gun then?

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Alert

Not Just Hams

But ANY applications below 106 / 212 and there can easily be harmonics.

It may also lock out proposals to use 42MHz to 86MHz properly.

For FM Radio Japan uses 76 to 90MHz and some countries around the 65MHz part of band.

The distance this can work at is limited (maybe 100m to 200m?), but not should be allowed for any above ground wiring. Actually fibre to the premises would make more sense.

Even current ADSL, ADSL2+ and VDSL is a problem on overhead wires.

But Ofcom and some others unlike ITU want to abolish ALL terrestrial broadcasting anyway. IP based services, cable and Satellite can't replace all Broadcast applications.

Aircraft uses 110 to 130 MHz approximately

Weather Satellites 137MHz

Marine 152 to 163 MHz approximately (Canals, rivers, lakes, not just Harbours, Estuaries, Shore).

There are other services too. Not just Radio Amateurs (50, 70, 145, 435 MHz small chunks) who are the least of the spectrum users between 1MHz and 430MHz..

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Re: Not Just Hams

Indeed.

I'd like to point out a small and insignificant user of various spots around 27Mhz, 35Mhz, 40Mhz, 459Mhz and 2.4Ghz. It's the radio-controlled models allocation.

These originally used 27Mhz alone. Then CB came and camped on that illegally, and the Home Office Radio Regulatory Board (as was) proved completely ineffectual (and uninterested) in doing anything about it, in spite of the fact that R/C modelers paid a license fee to use the slot.

Nowadays modelers might be flying jet turbine models capable of several hundred miles an hour, or FPV drones at several miles from their operators. Interference could be quite dangerous, in spite of the precautions which are routinely taken...

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Something people seem to be missing

It won't use the entire frequency band up to 100 MHz (or whatever figure they top out at) They can notch out whatever frequency ranges they wish to avoid interference. This is how DSL works now, if it didn't it would only work on 'perfect' phone lines. A lot of older plants have bridge taps and other impairments that will knock out certain frequency ranges.

The training phase of DMT identifies these impairments and avoids using those ranges. These ranges can also be programmed in, so if there is a strong VHF channel 4 in town, you might avoid using that, if there are certain bands used for police radio or FM or whatever, they can be avoided, etc.

The fight for amateur radio enthusiasts isn't against G.fast, because if they fight that battle they'll lose. They are a tiny minority, versus all the people who want faster internet. The proper battle is to identify some frequency ranges they think ought to be notched out, and work with their telco provider(s) in the area to see if they can reach a reasonable agreement.

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Re: Something people seem to be missing

Well that's the whole reason why small frequency allocations have already been identified for radio amateurs (and for other users) - so that the areas to be avoided are known. There's no need to have another discussion about it. And it's all very well automatically notching out some VHF channel that's active in the locality AFTER having caused interference to it during the learning process, but a lot the most interesting amateur radio activity involves extremely low power signals covering great distances. The chances of any of the local computer equipment noticing any of those activities and notching them out during its learning process seems pretty unlikely to me.

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RF Noise Levels are already very high.

As a Radio Ham who operates portable and mobile on HF, VHF and UHF all over the UK I know that noise levels in any built up area are already very high anyway; in central London noise reaches levels that are best described as staggering...

You have to be well out into the countryside to get reasonable noise levels and a really low noise floor is probably only possible in Northern Scotland.

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Anonymous Coward

Re: RF Noise Levels are already very high.

Yeah London is a pretty noisy place isn't it? And quite dirty and smelly and full of immigrants ;-)

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Re: RF Noise Levels are already very high.

Around here (Beds) the 80M noise level is S7+-, the 160M is also S7.

And thatś just through the powerline BT stuff.

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Re: RF Noise Levels are already very high.

I'm used to a S8 noise floor on 80m and 40m… sometimes S9+ in places.

I'm about 10km north-west of the Brisbane CBD.

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Silver badge
Unhappy

Talking about leaky house drop cables ...

Cable TV has been available in Canada for many years - in fact some Canadian companies were cable pioneers.

Early installations were somewhat 'ad hoc' being made before any standards had really been laid down. Often house drops were simply spaded in under lawn turf.

Now, some 40 years on, the cables are working their way to the surface and all it takes is a lawn mower to shave the shield/screen off the cable.

Often the first knowledge of this damage is from aircraft pilots who complain about TV programming they hear on their AM radios when coming in to land at Toronto International!

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Re: Talking about leaky house drop cables ...

"Early installations were somewhat 'ad hoc' being made before any standards had really been laid down. Often house drops were simply spaded in under lawn turf."

Early installations, eh? I think you'll find that's still how VerminMedia does drops.

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Bronze badge

Re: Talking about leaky house drop cables ...

Often the first knowledge of this damage is from aircraft pilots who complain about TV programming they hear on their AM radios when coming in to land at Toronto International!

And of course, if you thought television was bad watching it, you should hear what the FM carrier sounds like in AM!

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Bronze badge

Re: Talking about leaky house drop cables ...

That's the way it should be! I used to listen to the TV on the radio, until the d'd FM radio stations came in and swamped all the TV audio signal.

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Ion

Good Riddens

Personally think this kind of technology is hear to stay, and going by the quite frankly disgraceful response, from "Ham People" not on here but from other sites, mind, I will be glad to see them go. See most have a superiority complex in that they believe that there hobby is more important than the majority.

Average response is why don't you have Cat5/6? well guess what not everyone can afford a few thousand to have there house routed (and doing it urself looks rubbish unless inside the walls).

Also wireless is crap if ur concern is latency which is pretty much everyone but the most modest of users. So sometimes even wireless doesn't provide a solution (e.g. thick walls long distances).

Finally asking technology to slow down (and leave a space) for a quite frankly ancient technology is absurd. Yes you might have a "new" ham radio, but guess what that technology is ancient and dead and always will be.

More importantly than anything else by wanting these types of product dead, your effectively saying even though i live on a street of 20 houses my house is the important one and i should take priority (even though there may be 5 of those houses using the technology).

Put it simply if your using a Ham Radio you need to head back to the 1970's.

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Re: Good Riddens

You're talking about data over powerline devices within a property. This article is about data over telephone wires into the house - the delivery of internet services into a property.

Some similarities, but also some huge differences in the issues. For instance, modern "outside plant" is built with twisted pair wiring that has a reasonable degree of transmission-line characteristic at (low) radio frequencies. Mains cabling within a property has no such characteristic.

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