Dating your receivers - Page two
Size of the dial glass
The tuning dial on a radio is, without exception, the focal point on the front panel of a radio. Manufacturers often went to great lengths to make them as attractive as possible and as a collector I spend time glaring at the dial after I turn a set on as - it is sometimes too irresistable to ignore.
In the 1920's there was no such thing as a tuning dial as most of us know. Tuning was often done using several adjustments relying on calibrated scale markings of 1 to 100 which was never indicative of where a station might be located. Making a receiver was a science but tuning it was an artform.
After a while, manufacturers listened to people's tales about how difficult tuning a set was and they devised ways to make life alot easier for listeners. Manufacturers developed their own tuning indicators, using methods many and varied and the chants of 'our indicator is a better system than yours' became part of each manufacturers sales pitch. For the time being though, people saw the real solution as reducing the number of tuning knobs to one. The people won the battle for user-friendliness and the tuning method has changed little to this day.
In the late 1920's the tuning dial was a small wedged shaped hole where a disc with graduations marked 1 - 100 was displayed. Sometimes this was backlit but most of the time it wasn't. This made life easy because there was now only one tuning knob. These dials were not exactly dominant though.
At the start of the 1930's, tuning dials began to get slightly larger. The wedge shaped hole that I spoke about before gave way to either an arch shaped dial or a round dial, both being about 100mm in diameter. There were a few exceptions such as Breville, who made their dials slightly larger still but 100mm was more or less a benchmark for the time. In these later dials the disc with the dial markings no longer spun around to indicate the station. Instead a pointer, like a hand on a clock did this job. By this time most tuning dials were backlit with a 6.3 volt lamp. If the dial's disc was made of celluloid then it will invariably be burnt by the lamp, though fairly authentic-looking replacements are now made for some of the more common dials.
A little about why dials got bigger...
During the 1930's there was a big change on tuning dials - the introduction of station listings. Many countries moved from the 1 - 100 scale to frequencies and it is very common to see an overseas-made receiver to show 5.5 - 16 which meant 550 - 1600kHz tuning scale. Australia had a slightly larger frequency allocation though and most Class A stations (2FC, 3LO, 6WF, etc) could not be tuned on sets made overseas. The Australian MW band started at 530kHz which allowed for these stations. To make life easy, Australia's radio station call signs were printed on all future dials which meant that in some cases the dials had to be made bigger.
Most radio stations now use gimmicky names to identify themselves and this came to be after a relaxation of a law that required all stations to identify themselves by the callsign issued to them by the Commonwealth Government. So instead of a given station simply identifying as 2AB (fictitious) they'd now identify as something like 100.6 Blah Blah ~ Catchy Phrase Here ~ Blah Blah Blah (fictitious) - like I said, it's a gimmick and I can't really see where this habit attracts more advertisers and listeners. Back since the days of early broadcasting all stations identified with their callsign and these callsigns were organised to co-incide with the state/territory that the station was located in. Even though many stations don't identify themselves with their callsign, they are still issued with them and their transmitting facilities must be branded with them in some way. These are as follows:
AREA AM FM
Originally the Northern Territory used the number 5 as their prefix and the Australian Capital Territory used the 2 prefix but this was changed at some stage. Note how AM stations use two letters and FM stations use three. Of course, FM came along in the 1970's and therefore didn't appear on any valve sets in this country.
Knowing all this about station callsigns, you can assume that with Australia being a bloody big country that there would be alot of radio stations. There is. Even today the Commonwealth allocates a certain number of new broadcasting licences each year and they generally are sold by way of auction and can end up costing more than $100m each. Radio is big business and very competitive though I am not sure we need so many stations.
During the 1920's and 1930's, there were very few stations and while they each aimed their programming at local audiences, it was considered normal for interstate audiences to tune in. Some of my sets still pick up interstate stations quite well, all things considered, and given the number of stations we have now it is a bit surprising that it's still achievable. I often tune into Melbourne, Adelaide and Brisbane for a few minutes though most of the AM stations are networked these days so what you hear in Sydney is more or less being broadcast in the other states too.
Back to the dial sizes...
During the very late 1930's and throughout the 1940's radio tuning dials became fairly dominant features on most radios, large and small. Some examples are pictured below and the number of stations amplified the need for such large dials. Typically, the stations in the capital cities were given precedence, followed by all regional stations in a smaller font. Given that in those times, most stations provided their own programming, this convention was a little un-necessary in my view, but it was how things were done in this period.
1945 brought some more changes and radio manufacturers where faced with two challenges for the coming decade. One was to make radios smaller. At the time this was easier said than done. There was no minaturisation of components taking place and no-one really knew how to do so. It was a new manufacturing technique and took several years to become commonplace. 1949 saw the introduction of baseless valves where the pins came directly out of the glass envelope instead of the fragile wires which the base pins were soldered to. Baseless valves were generally faster to manufacture and were also stronger. This was the first sign that minaturisation would play a big role in radio manufacture during the 1950's. The late 1940's also saw the spawning of the humble small four valve mantel receivers. At first, these were still fitted with GT valves but during, thereabouts 1950-1951, the baseless valves gradually took over which gave the manufacturers the opportunity to install that all-important fifth valve to boost performance. The option was rarely exercised though because these mantel models were always intended to be marketed as second sets because most people had larger radios in their lounge/drawing rooms anyway. Four valve mantels were built to a price though for what they missed in circuitry, they still performed fairly well. The second challenge for manufacturers was to fit all of Australia's callsigns on the shrinking dials of the 1950's. It was never going to happen. On some sets, stations in small towns were simply left off the dial and it was a case of bad luck. After all, a manufacturer wasn't obliged to mark all stations on their dials - it was simply good practice to do so. A more commonly exercised option though, and probably more favourable to stations, was to regionalise the dials. AWA and Astor are two makers which come to mind straight away because they did just this. Each state had its own dial! Alternatively two states would share a dial, EG: NSW and QLD would be on one, as per the Radiola pictured below, VIC and TAS would be on another and SA and WA would be on the other one. Dials would be simply allocated to receivers on the production line depending on where that batch of sets would get sent. By the way, I didn't forget the NT and the ACT, it's a case of the mainland territories being grouped with NSW and SA respectively in those days. The Astor 'Football' is an example where the set had the slightly more expensive option of a dial for each state and a complete set of six o these receivers would be quite a valuable part of any collection. If your collection had Astor receivers holding a dominant place then it'd be ideal to have six of each dial across all the colours the sets came in and I think there were several colours in limited numbers. You could value such a collection in the tens of thousands I'd imagine because it would be very difficult and time-consuming to collect all possible combinations of dial and colour.
So now we know that after a period of grace, splendour and considerable expense and extravagence during the 1940's, radios began to become more conservative in their styling and presence. During the 1950' there was a general shift away from glass as a dial material to thermoplastics and with this came the ability to improve printing technology to a considerable degree. I've cleaned many dial glasses only to clean off the station markings with the dust and cobwebs, so a curse on the inventor of the inks used! This problem is yet to happen to me when cleaning a plastic tuning dial on a 1950's-1960's receiver so this was one of few benefits to come from the adoption of thermoplastics. Because of the ability to print more clearly it was possible to once again include all stations on one dial, reducing production costs and allowing one radio to be sold anywhere.
In summarising, the size of the tuning dial changed dramatically over the period in which valve radios were manufacturered and if you are familiar with the general aspects of what I have mentioned here, you can date any receiver to an accuracy of +-5 years just by looking at it from a distance. It's a simple matter of becoming familiar with the various types and shapes of tuning dials that existed over time.
Time and Date
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