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Long Wave radio era set to end with switch-off

economist.com

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Re: Long Wave radio era set to end with switch-off

#71

Post by microgpt »

TylerE wrote: post #49
gerdesj wrote: post #20

Earlier quoted context omitted.

We do spend out quite a lot here in the UK for the BBC. They could easily dump a couple of expensive presenters and use the savings for vacuum tubes, if that is what is needed. No idea where vacuum tubes were invented but I'm sure the BBC could find someone to make them.

I'm sure they could , but sourcing people willing to manufacture heavily equipment/processing intensive speciality products for tiny runs will be MINDBLOWINGLY expensive. This isn't about the little tubes that go in a guitar amp... we're talking about tubes that may well be too large for a single person to lift. What's more, everyone who knew how to build things is either dead or in a retirement home. You'd have to r…

At least you already have some working tubes to start from. Some guy did it with Nixie tubes, of course those are a lot smaller.

Re: Long Wave radio era set to end with switch-off

#72

Post by RobotToaster »

bilegeek wrote: post #29

IMO, when the last LW transmitter shuts down, the whole band needs to be reallocated to hams. Realistic small-ish antennas are shockingly doable with a capacitance hat, loading coil, and counterpoise.

Best we can do is privatisation and selling it to a party donor.

Re: Long Wave radio era set to end with switch-off

#73

Post by aeonik »

microgpt wrote: post #63
bilegeek wrote: post #29

IMO, when the last LW transmitter shuts down, the whole band needs to be reallocated to hams. Realistic small-ish antennas are shockingly doable with a capacitance hat, loading coil, and counterpoise.

I thought hams already had plenty of bands. Is there not one in this range?

There is a very small slice that amateur radio gets in this band, in theory it would be nice to have a bigger slice, but honestly, building antennas for this band to transmit anything worthwhile would be pretty hard.

My 7 Mhz antenna (HF, 40m band) is 67 feet long, and goes across by whole house.

The smallest antenna you could get away with for LF would be hundreds to thousands of feet long.

You might be able to go smaller if you enjoy suffering. Though, there are some pretty creative antenna designs that defy logic.

Re: Long Wave radio era set to end with switch-off

#74

Post by Symbiote »

microgpt wrote: post #67
andyjohnson0 wrote: post #45

Earlier quoted context omitted.

> No idea where vacuum tubes were invented but I'm sure the BBC could find someone to make them. The BBC has just cut its budget by £500 million, in an apparent attempt to limit the damage from the latest charter renewal process - which determines its funding. The new director general (ie ceo) is an ex-Google person, and they seem to be pivoting to become a social media content provider. So I'm pretty sure that spend…

I thought the license fee was a tax. You have to pay it, except in extremely specific scenarios that are basically just the bureaucracy's way of saying it's technically optional even though it isn't. AFAIK you have to own no devices capable of receiving BBC broadcasts - this includes most phones and computers since they broadcast on the internet.

You only need the license if you watch live TV (on any service) or use BBC iPlayer.

If you only watch DVDs, or stream movies etc, you don't need a license

Re: Long Wave radio era set to end with switch-off

#76

Post by BuildTheRobots »

mschuster91 wrote: post #19
reaperducer wrote: post #9

Earlier quoted context omitted.

Is that emitted power, consumed power, or effective radiated power? Without knowing that, your power calculations have no meaning. Radio stations are usually measured by the last of those: Effective radiated power. You can have a radio station with a 50,000 watt ERP, but running only a 2,500 watt transmitter. For FM radio stations, it's all about the height of the transmitter above average terrain. For AM, it's about…

> Is that emitted power, consumed power, or effective radiated power? Going by [1], emitted power. [1] https://www.bbceng.info/Operations/transmitter_ops/Reminisce...

I can't edit my previous comment (which incorrectly implied that the 3 stations at Droitwitch are going out of the same antenna), but I've done more research and have more information.

Droitwitch LW's antenna uses a T-aerial suspended between two 210m steel masts acting as massive capacitive top-loaded vertical monopole. The signal isn't beamed or shaped, it propagates omnidirectionally and this style of antenna offers _0 dB_ of ERP increase.

Even worse, they're transmitting AM, so the power output dynamically increases with the volume of the analogue audio being transmitted. If you cut off the input to Droitwitch, it'd still be putting out a 500kW carrier wave. When audio is applied the amplitude of the carrier is modulated, so for peak loudness (someone shouting or the loudest spike in music) it can take an extra 50% power to create the upper and lower sidebands - at peak, the Vapotron tubes could be putting out a combined 750kW.

The amplification stage is only ~70% efficient as well, so at peak power it's possible that the site is pulling nearly 1MW from the grid.

--

Compared to a modern UHF DTV transmitter station the differences are wild. The big transmitter near me is putting out 6* DTV MUX's at 174kW ERP each, but that's through a 15dBd UHF array at the top of the mast which gives an obscene amount of gain.

- Mains draw at the wall ~150kW (including cooling and ancillary systems).

- Total TPO (RF energy leaving the cabs) from each of the six transmitters is only ~52kW combined (8.7kW each)

- Output of the combiners after losses of ~0.5dB is ~46kW. We can expect another ~1.5dB of attenuation after forcing it up 300m of waveguide to the top of the tower so we're now sat at a "mere" ~33kW of RF energy going into the bottom of our antenna.

- 33kW with a +15dBd gain gets us to an ERP from the antenna of 1.044 MW.

--------------

Note: Numbers compiled from public sources. All mistakes and misunderstandings are mine. Whilst I do work in a tangentially related industry this is completely out of my area of expertise - in the same way that working as a cleaner at an aeroplane does not mean one knows how to fly or maintain a plane.

Re: Long Wave radio era set to end with switch-off

#77

Post by TylerE »

microgpt wrote: post #71
TylerE wrote: post #49

Earlier quoted context omitted.

I'm sure they could , but sourcing people willing to manufacture heavily equipment/processing intensive speciality products for tiny runs will be MINDBLOWINGLY expensive. This isn't about the little tubes that go in a guitar amp... we're talking about tubes that may well be too large for a single person to lift. What's more, everyone who knew how to build things is either dead or in a retirement home. You'd have to r…

At least you already have some working tubes to start from. Some guy did it with Nixie tubes, of course those are a lot smaller.

Exactly - and look what those cost despite being produced in relative quantity. Now scale up to something that's 1000 times the size with 1/1000th the production volume. Wouldn't surprise me if the per-tube cost was in the millions.

Nixies are also cold cathode, low current devices. Radio broadcast tubes can be handling tens or even hundreds of thousands of watts.

Re: Long Wave radio era set to end with switch-off

#78

Post by KaiserPro »

fredoralive wrote: post #51
dingaling wrote: post #34

Earlier quoted context omitted.

... on a patchwork off different frequencies across the UK due to the poor propagation of VHF

Doesn’t RDS mostly solve that for the most common case where frequency changes becomes an issue (car radios).

Yup, and DAB also still works.

Re: Long Wave radio era set to end with switch-off

#79

Post by sidderl »

http://websdr.ewi.utwente.nl:8901

One can listen to the live closure broadcast via this WebSDR website, by tuning it to AM 198 kHz.

"You are listening to 198 kHz longwave. BBC Radio 4 is no longer available on this frequency. However, you can find Radio 4 many other ways. You can find BBC Radio 4 online, via BBC Sounds. Radio 4 is available on DAB digital radio and through your digital television, including freely. Radio 4 is also available via FM radio, on 92 to 95 MHz and 103 to 105 MHz. Plus, you can listen via your smart speaker: just say 'play Radio 4'. Information on how to listen can be found on the BBC website, at bbc.co.uk/reception."

Re: Long Wave radio era set to end with switch-off

#80

Post by KaiserPro »

There is precisely one thing that keeps 198LW online: economy seven.

I think the reason why its been left on so long is that it took so long to migrate to digital meters https://tradehelp.gdhv.co.uk/support/solutions/articles/7900...

I am also annoyed that I missed the last signal.

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