Keeping radios working following analogue switch off.

[HamishBoxer]

To keep perfectly legal than as previously mentioned hard wire a very low output transmitter.And i am talking only a few milliwatt here, i stated earlier in a earlier posting i am not convinced it is allowed to run several watts or more into a dummy load.Having said that as long as it goes no further than a few feet within the building ,i dont see anyone complaining(or knowing).For me there is no way i wish to risk my amateur license,it took too much getting back in 1974.

David

[ppppenguin]

Not sure if leaky feeder has been suggested before. Implementation is simple. A length of rubbish quality co-ax (the sort with poor braid coverage) connected to the TX output. Far end terminated in a resistor.

This will give good signals within a few feet of the cable. If you run it around the house it should give decent signals inside and almost nothing outside. I base these comments on the Imperial College student radio in 1977. The steel frames of the halls of residence coupled well to the co-ax so you got best reception by putting your radio close to some structural steel. The signals also coupled to the steam pipes etc under Exhibition Road and could be received in the main college buildings if you put your set close to steelwork.

Suggest you don't use leaky feeder if you live in a tower block. All your neighbours will get a good signal too.

PS: Rather unexpectedly I found an online reference to the leaky feeder system at Imperial: http://www.crocclub.co.uk/mkii/page....ol=4&article=5

[kalee20]

Kalee99 (and others),

I bought a iTx transmitter kit a week ago, member OldTickTock brought this to my attention. It uses a 1R5 (=DK91) as modulated oscillator. Low powered so it's within the spirit of this Forum. I bought it (£39-95) because I wanted to compare its performance with a micropower 'pantry' transmitter of my own design.

I built it up on Saturday evening. Apart from an as yet unresolved anomaly of near-zero screen grid voltage on the 1T4 AF amplifier, which I'm overcoming with a potentiometer at present, it seems very promising. However, 'scoping the output shows a not very good sine-wave, so I'm expecting radiation on lots of harmonics and I'll be walking around with a portable SW radio to check how far any nuisance can be detected.

In order to not take this thread OT, I'm intending to start a new thread with a review (Mods - please intervene if necessary). But time is in short supply this week, so may be a fortnight before anything appears!

[Utility Matt]

Originally Posted by kalee20

I can see two things happening.

First, is that some enterprising company will make a set-top box type of thing, to convert DAB signals to AAB (analogue audio broadcast). Hopefully, this will offer outputs in the MW and FM broadcast bands.

Second, there may well be a big clear-out of existing radios by the masses, as they become redundant. So, we must all watch this carefully. I can't see the Mr Man-in-the-street, who has a couple of old radios that he'd always thought he'll get fixed one day, knowing how to find people like us - I can't abide the idea him thinking that now they're no use to anyone he might as well send them to landfill

Please note I am happy to take in any old bakelite EKCO radios to avoid the additional burden on the landfill sites!
I'm very interested in the idea of something to rebroadcast since I happen to like some of the stuff on, say, Radio 7, the older programmes! I will keep a look out with interest.
regards
Matt

[Tim]

Second, there may well be a big clear-out of existing radios by the masses, as they become redundant. So, we must all watch this carefully. I can't see the Mr Man-in-the-street, who has a couple of old radios that he'd always thought he'll get fixed one day, knowing how to find people like us - I can't abide the idea him thinking that now they're no use to anyone he might as well send them to landfill

Exactly what worries me!

[HamishBoxer]

We are though assuming Analogue turn off is really going to happen??

[Jimmyhaflinger]

Luckily, we're going to keep analogue radio broadcasts for many more years here in Italy (the few experimental DAB radio broadcasts are on the former VHF-III TV band and this was specifically done to allow the current FM analog broadcasts to continue unaltered)

Many old radios (virtually all Italian radios) have a "phono" input so it would be much easier to hook a DAB receiver's audio output there instead of fiddling with transmitters.

I'd leave DAB alone and use an Ipod anyway, there's almost no point in listening today's radio, be it analog or digital, lots of junky modern pop music and rarely anything interesting, i'd rather hook my radios to an Ipod loaded with my own music.

[A35Z5GT]

Greeting from the USA, first time poster...

I've been reading some of the posts about analogue broadcasting ceasing and thought I'd share a little tube transmitter I've built... Operates on 30v B+, so it isn't likely to get anyone in trouble... Heart is the 12EG6 tube that was used in hybrid auto radios of the 50s/60s... Other similar heptodes can be used(ex 12AD6), but the 12EG6 performs better... Only issue is it uses a 1Mc xtal osc for drive, I don't have any idea if that freq would be clear for users in Europe... Parts suppliers are in US, I suspect similar may be found at your preferred suppliers...

Schematic here:

http://members.cox.net/35z5gt/12eg6txrev.jpg

a couple pictures of construction...

http://members.cox.net/35z5gt/12EG6mod.jpg

http://members.cox.net/35z5gt/12EG6wiring.jpg

Tom Bryant

[Paul_RK]

Interested to read as part of the response to a recent petition to halt AM/FM switch-off, "The Government is working with manufacturers to consider the implementation of a ‘set-top box’ solution for analogue radio which would allow existing analogue radios sets to receive DAB". As only a small proportion of existing radios offer an audio input facility, this seems necessarily to imply some manner of micro-transmitter. Unless of course it's just deflective waffle

Paul

[HamishBoxer]

Thats intresting Paul

David

[HamishBoxer]

Nice TX Tom

David

[Phil G4SPZ]

How about a DAB receiver with a low-power amplitude modulated output around 460kHz? That would couple into most AM radios' IFs if placed close by, and not even need tuning in by the user.

[kalee20]

But it would only work for superhets, and even then only if the IF was of this order. Even just pre-war, there were still some being produced with IF's of around 120kHz!

[Phil G4SPZ]

True, but a modulated output tuneable from 120kHz to around 700kHz would enable coupling at IF or MW, to suit all applications.

I guess the problem is that 'manufacturers' would find this too expensive to implement, unless large sales could be guaranteed. They would probably prefer to sell complete new radios, rather than set-top adaptors for existing ones. A plug-in micro-power transmitter is probably the cheapest option all round.

Manufacturers, are you listening?!

[A35Z5GT]

It would require far more signal to "hit" the IFs, than the front end and as already stated, that system could not be used on a TRF... I suspect one is dreaming if he expects a large mfgr to build something for a small segment of the population, you guys are likely going have to build your own small Tx and keep them in the closet(or pantry as one poster referred to his)...

Analogue isn't going away in the US in the foreseeable future, but many of us old radio guys that want to listen to other than religious or talk programing on their BCB radios, have a small AM transmitter... Yes many have bought and built the SStrans AMT3000(nice unit, I have one) or other solid state Tx, but also are a fairly large segment who build their own... For myself it's more fun to use something constructed with valves, it's just "more proper"... I do have the advantage of recently "inheriting" the contents of a TV/radio shop that was in business from the 50s to the early '80s, so I have 99% of the parts on hand, and seldom need to buy anything for my projects... Prior Tx projects have been built using 50s UHF TV converters, as once gutted those already have a transformer, chassis and cabinet that are quite satisfactory for such projects...

Tom

[Jimmyhaflinger]

I think there's no point in making a DAB set-top-box,

Radios, unlike TVs, are small, inexpensive, and many are portable.
a DAB set top box may make (some) sense for a vintage radio collector, a lot less for the average radio user, and would be absolutely useless for portable radio users.

can you see someone buying a DAB set top box that costs as much as a new DAB radio (unless the gov subsidizes them) and that basically only allows his old FM radio to be used as a "wireless audio amplifier" for the DAB receiver? because you'll still need to fiddle with the DAB set top box to tune into your station, the old FM radio's tuning knob will only be needed to tune into the DAB STB's own frequency

[kalee20]

Well, maybe not for portable radios. But what about car radios? There were many CD players made with an FM modulator, to feed a standard FM car radio. Same with MP3 players. So why not DAB sets with an FM output? And if they are designed for 12V operation, then an extra socket for a plug-top type power supply would allow them to be used at home!

[A35Z5GT]

I could see the FM converter for auto usage becoming a reality and could be used for home use using a 12v power source(we call those plug in power packs "wall warts" here in the US, dunno the proper reference in the UK)... Still it's no help for older receivers of the MW or SW bands only...

Tom

[wireful3]

I have confused myself trying to decide what I would do when Analogue ceases. I do have a digital receiver but have difficulty deciding what I would wish to play through my analogue radios.

I think I would only need a converter for my FM radios. Unless the AM bands are blanketed with interference from whatever else replaces existing broadcasts, there are European stations that provide good enough signals in the evenings to use the radios as they were intended. For most of them SW is going to be available from almost anywhere in the world.

An FM "pantry transmitter" that would enable the all stages of the FM radio to be used is not a trivial home build. I don't know whether this will be needed as I gather units already exist along the lines Kalee suggests for car radios that give an FM output from a DAB receiver signal.

I agree with the other comments that say the economics of a set top box to feed an AM receiver make it unlikely. For the mass market I am sure manufacturers will aim for very low cost DAB sets. This is the way they went with FM radios

[Graeme Murphy]

I have already decided to just give up listening to radio when they turn off the signals.
I have tried DAB and the reception where I live is terrible.
I can only get a signal if the radio is sat upon the south facing windowsill yet according to the dab website I should have excellent reception !