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Old 16th Dec 2018, 1:58 am   #1
Croozer
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Default Power economy of valve vs. Dab - Arithmetical error??

A goodmans Dab radio came my way so I fed it with 6 D batteries to explore the joys of digital. But 'pleasures are like poppies spread, you seize the flower its bloom is shed' and the following day the battery was flat. A replacement was equally short lived.

Suspecting a fault, I measured the current and it drew the best part of a full amp! This seemed unbelievably high for a portable radio, so to get some idea about the parameters of this new digital world, I compared with the beefy wall wart on a Pure Evoke. 1000ma at 12V!

I measured the consumption of the 1964 HMV mw/lw kitchen transistor radio the Goodmans was to replace. 16mA on a pp9 for 198khz at a 'normal' listening volume.

Out of curiosity I wondered just how retrograde this change in power consumption was so I did a sum.

My R55 uses 4 valves with 1.4V 25mA heaters, the o/p has a double heater.

Lineup dk96 df96 daf96 dl96

HT 90V: 0.6ma 1.65ma 0.17ma 5ma

So. Comparison:

DAB Portable: 9W
1964 transistor portable 0.15W
1955 valve portable: 0.8W


Perhaps someone could check my arithmetic as my results defy logic, and I'm not immune to a misplaced decimal point.

A DAB radio is more than ten times less efficient and gets through batteries ten times faster than a 1950s valve radio? And a massive 50 times less economic than a first generation transistor set?
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Old 16th Dec 2018, 2:36 am   #2
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

I regard DAB radios as mains only sets.
You need a wheel barrow to carry the batteries if you take one out.
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Old 16th Dec 2018, 3:23 am   #3
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Like all radios nowadays (present company excepted) the main use is either in a car or, as you say, at home on mains power. Portable listening has largely transferred to the ubiquitous phone. Having said that, the latest models are said to be more economical.
Another drawback of early adoption of as was plain DAB.
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Old 16th Dec 2018, 3:35 am   #4
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Yes, I'm guessing the Goodmans in question is an early set, when around 8 hours from a set of D cells was the norm. I've just measured the battery consumption of my most recent DAB model, a Roberts Sovereign: 150mA while the display is illuminated, dropping to 100mA after a few seconds when the light goes out until a control is next adjusted. "Only" 600mW, then, from the four D cells, justifying the claimed 120-150 hours of battery life from a decent set of alkalines. Even so I returned them straight away to the LED lantern where they live...

Paul
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Old 16th Dec 2018, 3:36 am   #5
G8UWM-MildMartin
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Your arithmetic is near enough: I get it to nearer 0.9W for the valve portable, but not enough of a difference to argue about.
The tangential argument is whether it is cheaper to run a mains valve radio at, say, 40W consumption at 15p/kWh (0.6p/hr) giving a nice 3-W output than your 1964 transistor portable at 5p/ Ah for cheapest 1.5V alkaline cells x 6 for 9V = 30p for 9Wh. 3.333p/Wh x 0.15 = 0.5 p/hr. Again, close enough not to argue about.
The DAB portable would be very dear to run on batteries, but trivial on mains.
And B126 HT batteries for valve portables were dearer than complete transistor radios last time I bought one around 1979.(For a school trip to France on which transistor radios were banned, but they hadn't considered anyone would be eccentric enough to have a working valve portable...)
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Old 16th Dec 2018, 6:27 am   #6
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Quote:
Originally Posted by G8UWM-MildMartin View Post
(For a school trip to France on which transistor radios were banned, but they hadn't considered anyone would be eccentric enough to have a working valve portable...)
Love it!

School fails English comprehension test!

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Old 16th Dec 2018, 11:04 am   #7
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

I think this is implementation dependent. A lot of the DAB receivers were pretty much off the shelf modules with an audio amplifier and microcontroller attached by the vendor. Integration is a lot better now and they have somewhat more efficient ASICs. I have a USB stick sized receiver somewhere that lasts hours on a tiny Lipo Pack.

However all this pales in comparison to the HF DC receiver I built that takes 96mW!
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Old 16th Dec 2018, 3:24 pm   #8
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Quote:
Originally Posted by Radio Wrangler View Post
Quote:
Originally Posted by G8UWM-MildMartin View Post
(For a school trip to France on which transistor radios were banned, but they hadn't considered anyone would be eccentric enough to have a working valve portable...)
Love it!

School fails English comprehension test!

David
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Old 16th Dec 2018, 3:39 pm   #9
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

As Paul says, nearly 1A is possible for an early DAB set, though it's at the top end of the normal range. My Roberts RD60 does about 12 hours on a set of 4 alkaline D cells (or did - I don't really use it now). More recent chipsets are very much better, but still use a lot more power than a standard AM/FM analogue transistor radio.
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Old 16th Dec 2018, 3:51 pm   #10
Paul_RK
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

About the only solid state analogue portable here that might even be worse than early DAB models for power consumption is the early (1981/2) synthesized tuning Panasonic RF9000: twelve D cells, or 35 watts when powered by the mains.
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Old 16th Dec 2018, 5:35 pm   #11
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

I suspect that the batteries in the early dab sets may have been provided to retain the stored preselected station info when the mains was turned off. Stored stations were always lost unless batteries were present in the early examples I have come across.
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Old 16th Dec 2018, 5:53 pm   #12
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Storage technologies vary, but some early DAB models, for example the first Pure Evokes from the autumn of 2002, store pre-set stations indefinitely without having any facility for fitting batteries. In any case the current required for such a role wouldn't justify D cells or anything like: a couple of AAs would be more than sufficient. I'm pretty sure the main intention of providing batteries was to allow a degree of free-roaming portability, it's just that the cost of replacing them would have put most folk off making much use of the provision.

Paul
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Old 16th Dec 2018, 9:28 pm   #13
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

There is a Pure Evoke-1 in use, mainly for Radio 3, in my work room. (DAB+ services can be had on the computer.) In DAB terms it probably counts as vintage. The PSU is rated at 1.2A and runs warm. I have another Evoke-1 with a failed PSU. I wonder how close to the limit they run? I have a switched extension block and so switch it off at the mains. The Evoke-1 only has six presets but it has never lost them.
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Old 16th Dec 2018, 9:51 pm   #14
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

The Pure Evoke-1: another co-incidence! Only yesterday, one arrived here via a 3rd. party: did I want to buy it? A quick test indicates it is faulty: sounds very much like L.F. instability / motor-boating, but intermittent. So I took the back off to have a look inside: a number of elect. caps. were spotted: a couple are physically large. I now need to talk to the vendor; at present I do not know the asking price. However, if I do make an offer, that will have to reflect its condition.

Al.
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Old 16th Dec 2018, 10:09 pm   #15
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

DAB is about the only new technology I can think of for which I was a quite early adopter: well, at least once self-contained radios became generally available, as I ordered an Evoke-1 the first time they were offered by mail order in the Radio Times. I returned that first one after a couple of days as the on/off switch had only lasted that long. A high current to switch, and I think the switch must have been just a sprung contact moving across a printed board. The replacement set is fine to this day, but is used fairly sparingly.
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Old 16th Dec 2018, 11:17 pm   #16
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Quote:
Originally Posted by Paul_RK View Post
DAB is about the only new technology I can think of for which I was a quite early adopter
Me too (at least for a personal purchase). I had even considered a 'hi-fi stack' type tuner item that the RSGB were promoting in Rad Com in the late nineties. I had already concluded that the conventional radio landscape was contracting (Radio 2 was already taking a turn for the worse IMO) and I was desperate for the wider choice that this brave new platform promised.

The Evoke-1 gathered dust for a while in the mid noughties but has been in almost daily use since. I bought another later Pure 'woody' but it lost one of the stereo channels just inside the two year guarantee period. Pure said they couldn't repair it and that the model had been discontinued and so replaced it with a much better Tempus model (the same size as the Evoke) that also has FM but was still plain DAB. This has a different display and much smaller PSU than the Evoke and is in frequent use in another room.
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Old 17th Dec 2018, 7:09 am   #17
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

A DAB radio can indeed use appreciably more power than a reasonably efficient valve portable.
However for most people, battery cost is more important than watts. The large cells used in a modern radio are cheaper per watt hour than HT batteries.
Ready made HT batteries are of course no longer readily available, and I suspect that most people use a suitable number of small 9 volt batteries in series.
These cost more per watt hour than D cells.

Despite this, battery costs for a DAB set per hour would still exceed the costs for a valve portable.

My DAB set claims 30 hours service from 6 alkaline C cells, and whilst I have never logged the number of hours use actually achieved, the claimed figure seems about right.
Unfortunately, C cells have about half the energy content of D cells but cost about the same, thereby wiping out much of the gain from the somewhat reduced power consumption.
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Old 17th Dec 2018, 9:00 am   #18
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

I have wondered for quite a while as to whether DAB consumes more or less energy than am/fm. The DAB transmitters are much lower power than some of the am/fm ones, but there are only a few of them. The DAB radios consume proportionally a lot more power, and there are thousands of them. I wonder which total is greatest. Not being a "valve" person, I hadn't contemplated the relative power consumption of valve radios though
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Old 17th Dec 2018, 9:57 am   #19
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

Some time ago I pondered on here about the net effect of DAB on global warming, CO2 etc. It seems to save on the broadcaster's electricity bills at the expense of everyone else's. At a time when people are starting to get concerned by the consumption of things on standby, even the latest DAB receivers could be seen as quite un-green running from mains.

Run one from primary batteries and the greenies really will be after your blood!

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Old 17th Dec 2018, 10:10 am   #20
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Default Re: Power economy of valve vs. Dab - Arithmetical error??

I wasn't an earlier adopter as I mainly use R4 "on the move" and couldn't really see the point until I needed 6 Music for it's Dylan Radio Station [Theme Time Radio] and then 4xtra found it's feet on the Archive Front. I recall that many Forum Members hoped to be immediately out there in the workplace listening to the likes of The Navy Lark on 4xtra etc but experienced all these battery frustrations way back then. My first [brick sized] DAB set was definitely not portable but I didn't intend it to be re the battery "drain" issues. Hindsight is a wonderful thing though, if you have the benefit of it

I bought a job lot of relatively small Goodmans DAB sets [GMR1886] from a Supermarket offer fairly recently, mainly to be plugged in at the side of the bed for late night listening but I have used these on batteries as well. Not a frightening experience but I didn't test them to destruction. As said by others, the trend is to use other means for portable listening anyway! Ironically, I still tend to use my battered small Roberts R862 multi band set for portability. Short and Medium Wave access has gone after a series of accidents but the FM band remains.

Dave
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